CN111537579B - Electrochemical method for detecting formaldehyde based on rhodium oxide-nano porous nickel composite electrode - Google Patents
Electrochemical method for detecting formaldehyde based on rhodium oxide-nano porous nickel composite electrode Download PDFInfo
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Abstract
The invention provides rhodium oxide-nano porous nickel (Rh) capable of detecting formaldehyde2O3@ NPNi) composite electrode and a method for preparing the same. The invention adopts a template method to prepare the nano porous nickel electrode, and modifies rhodium oxide on the surface of the porous nickel electrode to obtain the rhodium oxide-nano porous nickel composite electrode. The electrode has a structure of compounding three-dimensional ordered nano porous nickel and high catalytic activity sheet rhodium oxide, a gas transmission channel is increased, and the sensitivity and the response speed of the electrode to formaldehyde are improved. The composite electrode has a stable structure, and no interface between the modification material and the electrode blocks the transmission of electrons, so that the composite electrode can be used for quickly detecting trace pollutant formaldehyde and can be used for a portable formaldehyde detection sensor.
Description
Technical Field
The invention belongs to the field of gas electrochemical detection, relates to an electrochemical method for detecting formaldehyde based on a rhodium oxide-nano porous nickel composite electrode, and particularly relates to rhodium oxide-nano porous nickel (Rh) for accurately and rapidly detecting trace formaldehyde pollutants2O3@ NPNi) composite electrode and a method for preparing the same.
Background
Formaldehyde (formaldehydes), the chemical formula HCHO, also known as Formaldehyde, a naturally occurring organic compound, is listed as "a substance that is strictly regulated in high-risk carcinogenesis". The formaldehyde has wide application, is a popular chemical product with simple production process and sufficient raw material supply, is the main stem of a downstream product tree of the methanol, about 30 percent of methanol in the world is used for producing the formaldehyde, and the annual output is about 2500 million tons.
Formaldehyde has pungent odor, can be smelled at low concentration, and has olfaction threshold of 0.06-0.07mg/m3. Long-term low concentration formaldehyde exposure can cause headache, dizziness, asthenia, sensory disturbance, hypoimmunity, and may cause sleepiness, hypomnesis or neurasthenia, mental retardationDepression and the like. The harm of long-term formaldehyde exposure to the respiratory system is also huge, and respiratory dysfunction and hepatotoxic lesion can be caused, which are shown as hepatocyte damage, liver radiation energy abnormality and the like. The newly decorated room has high formaldehyde content and is the main cause of many diseases.
In 2017, 10 and 27, in a carcinogen list published by the international cancer research institution of the world health organization, formaldehyde is put in a carcinogen list. In 2019, 7 and 23, formaldehyde is listed in the list of toxic and harmful water pollutants (first batch). In the national sanitary standard, the maximum limit value of indoor formaldehyde of a civil building is 0.08mg/m3. Therefore, accurate detection and control of formaldehyde concentration in the environment is of paramount importance.
At present, the types of sensors for formaldehyde detection are various, but most of formaldehyde sensors are greatly interfered by environmental humidity, the reference potential is easy to generate a 'drifting' phenomenon, the working stability is poor, and the precision and the reliability of formaldehyde detection are influenced. The electrochemical detection method has the advantages of quick response, high sensitivity, simple preparation, convenience in carrying and the like, and is the best method for quickly and accurately detecting molecules at present. The active catalytic material is supported on the electrode, reacts with the target analyte, and generates an electrical signal proportional to the concentration of the target analyte. The content of the measured object can be estimated by measuring the current or impedance of the electrode and other response parameters, and the method has good selectivity and sensitivity.
In the detection of formaldehyde, the nano porous material can obviously enhance the sensing capability. This enhancement is mainly due to material geometry characteristics such as irregularities, large specific surface area and high porosity, which makes more active sites on the electrode surface and increases the probability of charge transfer between the molecules and the electrode surface. Meanwhile, the in-situ modification technology is adopted, so that the stability of the structure and the performance of the electrode is ensured, and the electrode can be simultaneously used for accurately detecting trace formaldehyde in the environment and the water body.
Disclosure of Invention
The invention aims to solve the main technical problems that the existing formaldehyde sensor is influenced by humidity, has poor stability and low sensitivity and cannot detect the formaldehyde accurately, in particular to the problem that the formaldehyde of trace pollutants in the environment and water bodies cannot be detected accurately.
In order to solve the above technical problems, the present invention provides rhodium oxide-nanoporous nickel (Rh) capable of detecting formaldehyde2O3@ NPNi) composite electrode.
The rhodium oxide-nano porous nickel composite electrode comprises an electrode substrate and an electrode modification layer, wherein the electrode modification layer is rhodium oxide-nano porous nickel, rhodium oxide is specifically modified on the surface of the nano porous nickel, the specific structure is represented as a sheet structure containing microscopic holes and a surface layer, and the diameter of each hole is less than 50 nm.
The electrode adopts an electrochemical deposition method to modify rhodium oxide on the surface of the nano-porous nickel in situ, and the rhodium oxide-nano-porous nickel composite electrode is constructed. The electrode has a structure of three-dimensional ordered nano porous nickel and high catalytic activity sheet rhodium oxide phase composition, and a gas transmission channel is increased. Meanwhile, the in-situ modification technology ensures the stability of the electrode structure and the electrode performance, can realize the accurate detection of formaldehyde, and avoids the interference of humidity and the generation of potential drift. When the molecule is detected, the pore structure of the electrode is matched with the size of the detected molecule, so that the transfer diffusion of solute is easy, and the sensitivity and the response speed of the electrode to formaldehyde are improved. The composite electrode has a stable structure, no interface between the modification material and the electrode blocks the transmission of electrons, and the sensing response speed is greatly improved, so that the composite electrode can be used for quickly detecting trace pollutant formaldehyde.
The invention also aims to provide a preparation method of the rhodium oxide-nano porous nickel composite electrode capable of detecting formaldehyde.
The method specifically comprises the following steps:
s1, preparing a nano porous nickel modified electrode: preparing nano porous nickel on the surface of the electrode by adopting a template method;
s2, preparing a rhodium oxide-nano porous nickel composite electrode: the electrode decorated with the nano porous nickel is taken as a substrate, and an electro-deposition method is adopted to decorate a rhodium oxide layer on the surface of the nano porous nickel, so as to prepare the rhodium oxide-nano porous nickel composite electrode.
The template method is one of the preparation methods of the nano porous material, and is characterized in that the size and the shape of the nano porous material can be accurately controlled by controlling the shape of the template, so that the structure and the property of the electrode can be regulated and controlled. When the molecule is detected, the pore structure of the electrode is matched with the size of the detected molecule, so that the solute is easy to transfer and diffuse. The nano-aperture is suitable for detecting gas molecules, and the mesoporous aperture is suitable for detecting liquid molecules and biomacromolecules.
Further, in step S1, a polystyrene microsphere template is first prepared, and a nickel sheet is used as a substrate to perform electrophoretic deposition in the polystyrene microsphere emulsion with positive charges, so as to obtain the polystyrene template electrode. The template method specifically comprises the following steps: dispersing polystyrene microspheres with the diameter of 200-300nm in deionized water at the mass concentration of 1-5 wt% to form stable suspension; taking a polyimide copper clad laminate (Cu/PI) as a working electrode and a platinum sheet as a counter electrode, and carrying out electrophoretic deposition in 1-5 wt% of polystyrene microsphere emulsion, wherein the voltage of the electrodeposition is 3-5V, and the time is 5-10 min. And finally, drying the electrode at the temperature of 80-100 ℃ to obtain the polystyrene microsphere template. The deposition time determines the structure of the obtained nanopores, including the size and shape of the voids.
In the preparation process, the polyimide copper-clad plate needs to be ultrasonically degreased for 20-30min in acetone and then soaked in 0.4MNa2S2O8、0.1M CuSO4And 0.4M H2SO4Removing the surface oxide film in the solution. In order to protect the copper layer of the polyimide copper clad laminate, a protective layer nickel layer is electrodeposited on Cu/PI, and then a polystyrene template is electrodeposited.
Further, in step S1, the specific preparation method for preparing the nano-porous nickel is as follows: the prepared polystyrene microsphere template is used as a working electrode, a platinum sheet is used as a counter electrode, and the current density is set to be 10.0-15.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 2-5min, washing with deionized water, drying, and soaking the dried electrode in a chloroform solution for 20-30min to obtain the three-dimensional ordered nano porous nickel.
Further, in step S1, the plating solution for electrodepositing the metallic nickel layer may select nickel sulfate, nickel nitrate, and nickel sulfamate as the main salt of the metallic nickel. In the present invention, it is preferable to use 1.0 to 1.5M nickel sulfamate tetrahydrate, 0.02 to 0.05M nickel chloride and 0.3 to 0.6M boric acid.
Further, in step S2, depositing a rhodium metal layer on the nanoporous nickel electrode by using an electrodeposition method, and then constructing Rh by using an anodic oxidation method2O3@ NP Ni electrode. The specific method for preparing the ruthenium oxide modification layer comprises the following steps: using nano porous nickel as cathode and titanium net as anode, setting current density at 0.8-1.2A/dm2And carrying out electrodeposition treatment at the temperature of 35-65 ℃, preferably 38-45 ℃ for 5-20min, preferably 5-10min to obtain the rhodium-nano porous nickel composite electrode, and then putting the rhodium-nano porous nickel composite electrode into an alkaline solution for anodic oxidation treatment to obtain the rhodium oxide-nano porous nickel composite electrode. The electrodeposition time is too long, and the prepared rhodium oxide coating is thick, so that the porous structure of the bottom layer is completely covered, and the sensing response characteristic of the electrode can be influenced.
Further, in step S2, the electrodeposition bath for preparing the rhodium-nanoporous nickel composite electrode comprises: 2-3g/L of rhodium sulfate and 20-25g/L of sulfuric acid.
Further, in step S2, the anodic oxidation method specifically includes: the rhodium-nano porous nickel composite electrode is used as an anode, stainless steel is used as a cathode, and the concentration is 0.3-0.6A/dm2Oxidation reaction is carried out for 5-10min under current density.
Further, in step S2, the alkaline solution may be selected from common inorganic bases, preferably 1-2M KOH.
The rhodium oxide-nano porous nickel composite electrode prepared by the method can be used for quickly detecting trace pollutant formaldehyde and can be used for a portable formaldehyde detection sensor.
Scanning and observing the surface appearance of the rhodium oxide-nano porous nickel composite electrode prepared by the method by adopting an SEM electron microscope.
FIG. 1 is an SEM topography of a rhodium oxide-nanoporous nickel composite electrode obtained during the preparation of example 1. Wherein, FIG. 1(a) is an SEM image of a polyethylene template, and FIG. 1(b) is an SEM image of porous nickel, and it can be seen from the SEM image that the pores on the surface of the electrode are uniformly distributed and orderly arranged. After the surface of the porous nickel is modified with rhodium oxide, the electrode structure is greatly changed, as shown in fig. 1(c), a rhodium oxide-nano porous nickel composite electrode structure combining nano-porous and lamellar is formed, and the diameter of the pores is less than 50 nm.
And (3) testing the response performance of the rhodium oxide-nano porous nickel composite electrode prepared by the method of the invention for detecting formaldehyde by adopting methods of cyclic voltammetry, differential pulse voltammetry and the like.
FIG. 2 is a plot of cyclic voltammetry curves of the rhodium oxide-nanoporous nickel composite electrode prepared in example 1 at various scan rates in KOH solution containing 10mM formaldehyde, where the scan rate is between 10mV/s and 100 mV/s. As can be seen from the figure, when the scanning speed is gradually increased, the peak current density is also increased, which shows that the rhodium oxide-nano porous nickel composite electrode prepared by the invention has response performance to formaldehyde and can detect trace formaldehyde in water.
FIG. 3 is a plot of the chronoamperometric response of the rhodium oxide-nanoporous nickel composite electrode prepared in example 2 to a lower concentration of formaldehyde. As can be seen from the figure, the response sensitivity of the electrode is gradually increased along with the increase of the concentration of formaldehyde, which shows that the rhodium oxide-nano porous nickel composite electrode prepared by the invention can realize the rapid detection of trace formaldehyde.
Fig. 4 is a timing current curve diagram of the anti-interference test of the rhodium oxide-nano porous nickel composite electrode prepared in example 2. Common interferents such as ethanol, acetic acid, methanol and formic acid are used for testing whether the electrode has enough anti-interference performance, specifically, a timing current method (CA) is used, formaldehyde and the interferents are added into 0.1M KOH solution at equal time intervals, and the electrocatalysis effect of the rhodium oxide-nano porous nickel composite electrode on the interferents is judged by analyzing the change condition of current density. As can be seen from the figure, obvious current response is generated after formaldehyde is added, but no obvious current change is generated after the interference substances are added, so that the rhodium oxide-nano porous nickel composite electrode prepared by the method has good anti-interference performance and can detect formaldehyde in a complex test environment.
FIG. 5 is an electrochemical response diagram of stability test of the rhodium oxide-nanoporous nickel composite electrode prepared by the invention. Specifically, 11 composite electrodes were prepared in sequence by the same method and procedure under the same conditions, and formaldehyde response test was performed under the same conditions to record data. The Relative Standard Deviation (RSD) of the 11 electrochemical response values is 3.84 percent, so that the rhodium oxide-nano porous nickel composite electrode prepared by the invention has excellent stability and can realize accurate detection of formaldehyde.
The invention has the beneficial effects that:
(1) high response performance: the rhodium oxide is modified on the surface of the nano-porous nickel in situ, a rhodium oxide-nano-porous nickel composite electrode is constructed, and a surface modification layer of the electrode has the synergistic catalytic action of three-dimensional ordered nano-holes and surface high-activity substances, so that the detection sensitivity is greatly improved, and the problem that the sensitivity and the accuracy of the existing formaldehyde sensor are not enough is solved.
(2) And (3) accurate detection: by adopting the in-situ modification technology, the stability of the structure and the performance of the electrode is ensured, and the interference of humidity and the generation of potential drift phenomena are avoided. No interface between the modification material and the electrode blocks the transmission of electrons, the sensing response speed is greatly improved, the accurate detection of formaldehyde is realized, and the problem of insufficient detection stability of the existing formaldehyde sensor is solved.
(3) The application field is wide: the electrode preparation process is simple and easy to implement, and the electrode structure can be regulated and controlled to be simultaneously used for quickly detecting trace formaldehyde in the environment and the water body.
Drawings
The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.
FIG. 1 is an SEM topography of a rhodium oxide-nanoporous nickel composite electrode prepared by the invention. Wherein fig. 1(a) is an SEM image of a polyethylene template, fig. 1(b) is an SEM image of porous nickel, and fig. 1(c) is an SEM image of a rhodium oxide-nanoporous nickel composite electrode;
FIG. 2 is a cyclic voltammogram of different scanning rates of a rhodium oxide-nanoporous nickel composite electrode prepared according to the invention in a KOH solution containing 10mM formaldehyde;
FIG. 3 is a plot of the chronoamperometric response of the rhodium oxide-nanoporous nickel composite electrode prepared according to the invention to formaldehyde of lower concentration;
FIG. 4 is an anti-interference test of the rhodium oxide-nano porous nickel composite electrode prepared by the invention for detecting formaldehyde;
FIG. 5 is a stability test of the rhodium oxide-nanoporous nickel composite electrode prepared by the invention for detecting formaldehyde.
Detailed Description
In order that the objects, aspects and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the following detailed description and the accompanying drawings.
Example 1
Preparing a rhodium oxide-nano porous nickel composite electrode:
(1) preparation of porous nickel: the template method is adopted to prepare the nano porous nickel, and the specific method comprises the following steps: firstly, polystyrene microspheres with the diameter of 200-300nm are dispersed in deionized water at the mass concentration of 1-5 wt% to form a stable suspension. And (3) taking a polyimide copper-clad plate as a working electrode and a platinum net as a counter electrode, and carrying out electrophoretic deposition in the prepared polystyrene microsphere emulsion, wherein the voltage of the electrodeposition is 3V, and the time is 10min to obtain the polystyrene microsphere template. Then preparing an electrodeposition nickel plating solution, specifically 1.0M nickel sulfamate tetrahydrate, 0.02M nickel chloride and 0.3M boric acid. The polystyrene microsphere template is used as a working electrode, the platinum sheet is used as a counter electrode, and the current density is set to be 15.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 5 min. Then washed by deionized water and dried. And (3) soaking the dried electrode in a chloroform solution for 30min to obtain the three-dimensional ordered porous nickel electrode.
(2) Preparing a rhodium oxide-nano porous nickel composite electrode: the prepared nano porous nickel electrode is used as a substrate, and an electro-deposition method is adopted to modify a rhodium oxide layer on the surface of the porous nickel to construct a rhodium oxide-nano porous nickel composite electrode. The specific method comprises the following steps: preparing rhodium plating solution, specifically 2g/L rhodium sulfate,sulfuric acid 20 g/L. The nano porous nickel electrode is used as a cathode, the titanium net is used as an anode, and the current density is set to be 1.2A/dm2And the temperature is 38 ℃, and the electrodeposition time is 5min, thus obtaining the rhodium-nano porous nickel electrode. Then the electrode is subjected to anodic oxidation in 2M KOH alkaline solution, a rhodium-nano porous nickel electrode is used as an anode, stainless steel is used as a cathode, and the concentration of the rhodium-nano porous nickel electrode is 0.5A/dm2And oxidizing for 10min under the current density to obtain the rhodium oxide-nano porous nickel composite electrode.
Example 2
Preparing a rhodium oxide-nano porous nickel composite electrode:
(1) preparation of porous nickel: the template method is adopted to prepare the nano porous nickel, and the specific method comprises the following steps: firstly, polystyrene microspheres with the diameter of 200-300nm are dispersed in deionized water at the mass concentration of 1-5 wt% to form a stable suspension. And (3) taking a polyimide copper-clad plate as a working electrode and a platinum net as a counter electrode, and carrying out electrophoretic deposition in the prepared polystyrene microsphere emulsion, wherein the voltage of the electrodeposition is 5V, and the time is 5min to obtain the polystyrene microsphere template. Then preparing an electrodeposition nickel plating solution, specifically 1.5M nickel sulfamate tetrahydrate, 0.05M nickel chloride and 0.6M boric acid. The polystyrene microsphere template is used as a working electrode, the platinum sheet is used as a counter electrode, and the current density is set to be 10.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 2 min. Then washed by deionized water and dried. And (3) soaking the dried electrode in a chloroform solution for 30min to obtain the three-dimensional ordered porous nickel electrode.
(2) Preparing a rhodium oxide-nano porous nickel composite electrode: the prepared nano porous nickel electrode is used as a substrate, and an electro-deposition method is adopted to modify a rhodium oxide layer on the surface of the porous nickel to construct a rhodium oxide-nano porous nickel composite electrode. The specific method comprises the following steps: preparing rhodium plating solution, specifically 2g/L rhodium sulfate and 20g/L sulfuric acid. The nano porous nickel electrode is used as a cathode, the titanium net is used as an anode, and the current density is set to be 1.0A/dm2And the temperature is 45 ℃, and the electrodeposition time is 8min, thus obtaining the rhodium-nano porous nickel electrode. Then the electrode is subjected to anodic oxidation in 2M KOH alkaline solution, a rhodium-nano porous nickel electrode is used as an anode, stainless steel is used as a cathode, and the reaction temperature is 0 DEG C.6A/dm2And oxidizing for 8min under the current density to obtain the rhodium oxide-nano porous nickel composite electrode.
Example 3
Preparing a rhodium oxide-nano porous nickel composite electrode:
(1) preparation of porous nickel: the template method is adopted to prepare the nano porous nickel, and the specific method comprises the following steps: firstly, polystyrene microspheres with the diameter of 200-300nm are dispersed in deionized water at the mass concentration of 1-5 wt% to form a stable suspension. And (3) taking a polyimide copper-clad plate as a working electrode and a platinum net as a counter electrode, and carrying out electrophoretic deposition in the prepared polystyrene microsphere emulsion, wherein the voltage of the electrophoretic deposition is 5V, and the time is 5min, so as to obtain the polystyrene microsphere template. Then preparing an electrodeposited nickel solution, specifically 1.0M nickel sulfamate tetrahydrate, 0.02M nickel chloride and 0.3M boric acid. The polystyrene microsphere template is used as a working electrode, the platinum sheet is used as a counter electrode, and the current density is set to be 12.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 3 min. Then washed by deionized water and dried. And (3) soaking the dried electrode in a chloroform solution for 20min to obtain the three-dimensional ordered porous nickel electrode.
(2) Preparing a rhodium oxide-nano porous nickel composite electrode: the prepared nano porous nickel electrode is used as a substrate, and an electro-deposition method is adopted to modify a rhodium oxide layer on the surface of the porous nickel to construct a rhodium oxide-nano porous nickel composite electrode. The specific method comprises the following steps: preparing rhodium plating solution, specifically 3g/L of rhodium sulfate and 25g/L of sulfuric acid. The nano porous nickel electrode is used as a cathode, the titanium net is used as an anode, and the current density is set to be 1.2A/dm2And the temperature is 38 ℃, and the electrodeposition time is 5min, thus obtaining the rhodium-nano porous nickel electrode. Then the electrode is subjected to anodic oxidation in 2M KOH alkaline solution, a rhodium-nano porous nickel electrode is used as an anode, stainless steel is used as a cathode, and the concentration of the rhodium-nano porous nickel electrode is 0.5A/dm2And oxidizing for 10min under the current density to obtain the rhodium oxide-nano porous nickel composite electrode.
Example 4
Preparing a rhodium oxide-nano porous nickel composite electrode:
(1) preparation of porous nickel: the template method is adopted to prepare the nano porous nickel, and the specific methodComprises the following steps: firstly, polystyrene microspheres with the diameter of 200-300nm are dispersed in deionized water at the mass concentration of 1-5 wt% to form a stable suspension. And (3) taking a polyimide copper-clad plate as a working electrode and a platinum net as a counter electrode, and carrying out electrophoretic deposition in the prepared polystyrene microsphere emulsion, wherein the voltage of the electrodeposition is 5V, and the time is 5min to obtain the polystyrene microsphere template. Then preparing an electrodeposition nickel plating solution, specifically 1.5M nickel sulfamate tetrahydrate, 0.05M nickel chloride and 0.6M boric acid. The polystyrene microsphere template is used as a working electrode, the platinum sheet is used as a counter electrode, and the current density is set to be 10.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 2 min. Then washed by deionized water and dried. And (3) soaking the dried electrode in a chloroform solution for 30min to obtain the three-dimensional ordered porous nickel electrode.
(2) Preparing a rhodium oxide-nano porous nickel composite electrode: the prepared nano porous nickel electrode is used as a substrate, and an electro-deposition method is adopted to modify a rhodium oxide layer on the surface of the porous nickel to construct a rhodium oxide-nano porous nickel composite electrode. The specific method comprises the following steps: preparing rhodium plating solution, specifically 2g/L rhodium sulfate and 20g/L sulfuric acid. The nano porous nickel electrode is used as a cathode, the titanium net is used as an anode, and the current density is set to be 0.8A/dm2And the temperature is 45 ℃, and the electrodeposition time is 10min, thus obtaining the rhodium-nano porous nickel electrode. Then the electrode is subjected to anodic oxidation in 2M KOH alkaline solution, a rhodium-nano porous nickel electrode is used as an anode, stainless steel is used as a cathode, and the concentration of the rhodium-nano porous nickel electrode is 0.6A/dm2And oxidizing for 5min under the current density to obtain the rhodium oxide-nano porous nickel composite electrode.
Example 5
And (3) testing the stability of the rhodium oxide-nano porous nickel composite electrode:
following the procedure of example 1 above, 11 composite electrodes were prepared in sequence under the same conditions and formaldehyde response tests were performed under the same conditions and the data recorded as follows.
Example 6
The rhodium oxide-nanoporous nickel composite electrodes prepared in the above examples 1-4 were used in combination with a gas sensor to perform actual tests for trace formaldehyde. Specifically, a portable formaldehyde gas detection instrument of a commercial product was purchased from Guangzhou Yu core sensing technology, Inc., and the composite electrodes prepared in examples 1 to 4 were sequentially inserted into the instrument according to the method of using the instrument, and the detection of trace formaldehyde gas in the environment was performed under the same conditions, and data was recorded, as shown in the following table.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single technical solution, and such description is for clarity only, and those skilled in the art should take the description as a whole, and the technical solutions in the embodiments may be combined appropriately to form other embodiments that those skilled in the art can understand. The technical details not described in detail in the present invention can be implemented by any of the prior arts in the field. In particular, all technical features of the invention which are not described in detail can be achieved by any prior art.
Claims (10)
1. An electrochemical method for detecting formaldehyde based on a rhodium oxide-nano porous nickel composite electrode is characterized in that the rhodium oxide-nano porous nickel composite electrode comprises an electrode substrate and an electrode modification layer, the electrode modification layer is rhodium oxide-nano porous nickel, the rhodium oxide-nano porous nickel modification layer is formed by modifying rhodium oxide on the surface of the nano porous nickel, and the specific structure of the rhodium oxide-nano porous nickel modification layer is a sheet structure containing micro holes and a surface layer.
2. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 1, wherein the diameter of the pores is less than 50 nm.
3. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 1 or 2, wherein the preparation method of the rhodium oxide-nano porous nickel composite electrode comprises the following steps:
s1, preparing a nano porous nickel modified electrode: preparing nano porous nickel on the surface of the electrode by adopting a template method;
s2, preparing a rhodium oxide-nano porous nickel composite electrode: the electrode decorated with the nano porous nickel is taken as a substrate, and an electro-deposition method is adopted to decorate a rhodium oxide layer on the surface of the nano porous nickel, so as to prepare the rhodium oxide-nano porous nickel composite electrode.
4. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 3, wherein in step S1 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the template method specifically comprises: dispersing polystyrene microspheres with the diameter of 200-300nm in deionized water at the mass concentration of 1-5 wt% to form a stable suspension; and (3) depositing the polystyrene colloid for 5-10min under the condition of 3-5V by taking the polyimide copper-clad plate as a working electrode and the platinum net as a counter electrode to obtain the polystyrene microsphere template.
5. An oxidation based composition according to claim 4The electrochemical method for detecting formaldehyde by using the rhodium-nano porous nickel composite electrode is characterized in that in the step S1 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the specific preparation method of the nano porous nickel is as follows: the prepared polystyrene microsphere template is taken as a working electrode, a platinum sheet is taken as a counter electrode, and the current density is set to be 10.0-15.0mA/cm2And electrodepositing a metal nickel layer on the polystyrene template for 2-5min, washing with deionized water, drying, and soaking the dried electrode in a chloroform solution for 20-30min to obtain the three-dimensional ordered nano porous nickel.
6. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 5, wherein in the step S1 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the plating solution for electrodepositing the metallic nickel layer comprises: 1.0-1.5M nickel sulfamate tetrahydrate, 0.02-0.05M nickel chloride and 0.3-0.6M boric acid.
7. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 3, wherein in step S2 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the specific method for preparing the rhodium oxide modification layer is as follows: using nano porous nickel as cathode and titanium net as anode, setting current density at 0.8-1.2A/dm2And carrying out electrodeposition treatment at the temperature of 38-45 ℃ for 5-10min to obtain the rhodium-nano porous nickel composite electrode, and then putting the rhodium-nano porous nickel composite electrode into an alkaline solution for anodic oxidation treatment to obtain the rhodium oxide-nano porous nickel composite electrode.
8. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 7, wherein in the step S2 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the electrodeposition bath consists of: 2-3g/L of rhodium sulfate and 20-25g/L of sulfuric acid.
9. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nano porous nickel composite electrode as claimed in claim 7, wherein in step S2 of the preparation method of the rhodium oxide-nano porous nickel composite electrode, the anodic oxidation method specifically comprises: the rhodium-nano porous nickel composite electrode is used as an anode, stainless steel is used as a cathode, and the concentration is 0.3-0.6A/dm2Oxidation reaction is carried out for 5-10min under current density.
10. The electrochemical method for detecting formaldehyde based on the rhodium oxide-nanoporous nickel composite electrode as claimed in claim 7, wherein in the step S2 of the preparation method of the rhodium oxide-nanoporous nickel composite electrode, the alkaline solution is 1-2M KOH.
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