| Ethanol is a non-toxic and renewable chemical raw material.Compared with traditional gasoline and hydrogen,ethanol has a higher energy density,which is more in line with the requirements of modern society for new energy.In addition,due to the necessity of controlling drunk driving,the detection of trace amounts of ethanol has also given rise to a research boom in recent years.In this work,a three-dimensional ethanol electrocatalytic electrode is prepared based on the substrate of macroporous conductive network(MECN)using a novel liquid flow deposition technique,and its performance in direct ethanol fuel cells(DEFCs)and ethanol electrochemical sensors is explored as well.The main work is as follows:First,siliconmicro-channelplate(Si-MCP)isfabricatedusing microelectromechanical systems(MEMS)and its three-dimensional porous structure can provide a large surface area gain for the electrodes.Then,the nickel and palladium nanoparticles are sequentially deposited onto the outer surface and the inner walls of Si-MCP using the liquid flow deposition technique to form MECN and palladium-modified three-dimensional electrode(Pd/MECN),respectively.Finally,the electrode is subjected to a rapid thermal processing(RTP)operation to bind palladium and nickel plating closer,and at the same time form a palladium-nickel alloy at the interface.In order to highlight the influence of liquid flow deposition on the performance of the electrode,the electrode samples fabricated by vacuum electroless plating and electroplating respectively are also prepared for reference.Morphology and structural characterization show that liquid flow deposition can improve the uniformity,compactness and spreadability of the coating,so that the surface area of electrode which can participate in the electrochemical reaction is larger.At the same time,the alloy degree between palladium and nickel of the sample prepared by liquid flow deposition is also higher,which is conducive to the electrocatalytic activity of the electrode.The Pd/MECN electrode is performed with a series of electrochemical tests in an alkaline fuel cell environment.The results show that the sample fabricated by liquid flow deposition has the highest electrocatalytic activity for ethanol,and the current density of ethanol oxidation peak can be 553 mA/cm~2,3.5 times and 34.5 times larger than that of samples fabricated by vacuum electroless deposition and electrodeposition,respectively.Electrochemical operating stability of such a sample is also the best,and its performance degradation is very small after the continuous scanning in the working environment for 13 hours.The optimum values of concentration(including the electrolyte concentration and the ethanol concentration)in DEFCs based on Pd/MECN electrode are also extracted in this work and the corresponding kinetic mechanisms are systematically analyzed,results showing that when the concentration of alkaline electrolyte and ethanol is comparable,the electrooxidation efficiency of ethanol is the most excellent.What's more,when the Pd/MECN electrode made by liquid flow deposition is applied to an ethanol electrochemical sensor,it owns excellent performance as well.Among that,the detection sensitivity of the sensor is 0.85 mA/mM/cm~2,which is much higher than that of its reference samples.After the prolonged cycling voltammetry test,the sensor's detection current density decreased by only 0.038%per circle on average,indicating that the liquid flow deposition has also improved the stability of such a sensor.Finally,the electrochemical behaviors of the detecting electrode surface are analyzed by electrochemical impedance spectroscopy(EIS)and alternating-current impedance(Z-V)tests,and it has been demonstrated qualitatively and quantitatively that the liquid flow deposition enriches the active sites on three-dimensional electrode surface.In a word,the above characterization results and excellent performance make the liquid flow deposited Pd/MECN electrode have a high application value in the field of DEFCs and ethanol electrochemical sensors. |
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