Electrocatalytic Performance Of Ru-based Oxides In Acidic System

Hydrogen,as an alternative to fossil fuels,is the ideal clean energy source.Water splitting to produce molecular hydrogen is a promising method to store to store electric energy.The water splitting consists of two half-cell reactions such as hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.However,the high overpotential of anodic and the slow kinetics restricts the development of hydrogen economy.Recently,OER catalysts have been widely studied in alkaline,promoting the rapid development of hydrogen production.In comparison,the design of durable and performance acid OER catalysts is still very slow,which greatly restricts the popularization and application of water splitting in acid.Therefore,this work starts from the synthesis of high-performance RuO₂-based OER catalyst and the selective oxidation of methanol to replace OER process,and tries to alleviate the restriction of energy consumption for water splitting in acidic conditions.The main research results are as follows:1.Zn-doped RuO₂（py-RuO₂:Zn）nanowire array catalyst was prepared directly on Ti substrate by pyrolysis method.Through characterization and testing,it was found that the introduction of Zn element regulated the morphology of RuO₂,reduced the crystal size of the catalyst,increased the electrochemical active surface area of the catalyst,and increased the number of active sites.The OER activity of py-RuO₂:Zn was greatly increased.The overpotential and Tafel slope of py-RuO₂:Zn are 175m V@10 m A cm^-2and 38.9 m V dec^-1in 0.5 mol L^-1H₂SO₄electrolyte solution.It was significantly better than commercial RuO₂(295 m V and 49.7 m V dec^-1),and showed excellent acid OER catalytic activity.In the stability evaluation,py-RuO₂:Zn can run stably for 1000 hours at the current density of 10 m A cm^-2and more than 100hours at the current density of 50 m A cm cm^-2,indicating that the catalyst also has excellent catalytic stability.2.The CeO₂/RuO₂ methanol oxidation catalyst was prepared by pyrolysis method.The methanol oxidation reaction was used to replace the slow OER and was coupled with HER.This reaction could catalyze methanol oxidation to produce value-added formic acid（HCOOH）at the anode and high purity H₂at the cathode.Through characterization and testing,it was found that the introduction of CeO₂could be used as the active site of water activation,while RuO₂was used as the active site of methanol oxidation,and the two cooperated to complete methanol oxidation reaction.In H₂SO₄(0.5 mol L^-1electrolyte solution containing CH₃OH(2.5 mol L^-1),the methanol oxidation potential of CeO₂/RuO₂is only 1.195 V（vs RHE）,much lower than 1.405 V on pyrolytic pure RuO₂（py-RuO₂）.The negative potential shift was about 300 m V compared with OER(1.494 V@10 m A cm^-2)of c-RuO₂.In addition,the selectivity of formic acid was more than 50%in a wide potential range of 1.32～1.52 V.When the potential was 1.32 V,the current efficiency of formic acid was53.7%.Futrther,in Methanol-water electrolyzer,a cell voltage of 1.308 V was obtained at 10 m A cm^-2,about 260 m V smaller than that of 1.570 V for Pt/C（HER）||py-Ru O2（OER）cell and corresponding to a 16.7%reduction in energy input for H2 generation under the conditions.The selective oxidation of methanol to formic acid shows great potential as a substitute for acid OER process,which can significantly reduce the cost of hydrogen production from water splitting.