Mechanism Of Rare Earth Phosphate To Regulate Electrochemical Hydrrogen Evolution Reaction Of Mloybdenym Phosphide Electrocatalyst

The excessive fossil fuel depletion and concomitant environment contamination drive the development of clean and renewable energy sources.Hydrogen,as a renewable energy carrier with good thermal conductivity,high combustion value,large energy density and convenient storage,is considered to be one of the most promising replacements of carbon-based fuels.However,the high hydrogen evolution overpotential of the electrolytic electrode leads to the high-power consumption and production cost.Therefore,it is of great significance to develop novel,efficient,and universal synthetic methods to fabricate high-performance,low-cost electrode materials with low overpotentials,and thus reduce energy consumption.In this paper,a controlled construction method for three-dimensional self-supporting monolithic rare earth CePO₄ modified MoP electrode materials were developed.We designed and synthesized a series of high-performance MoP electrode materials modified with rare earth CePO₄,heteroatomic doping and carbon-based composite.The regulation of phase,composition,structure,size/morphology,three-dimensional structure,doping ions and doping behavior of catalyst were investigated.Theoretical calculations verified the composition-structure-performance relationship of how rare earth CePO₄ modified MoP electrode material,and clarified the mechanism of the rare earth CePO₄ regulates the electrocatalytic activity of MoP electrode materials.Electrochemical hydrogen evolution performance tests showed that the electrode material had an overpotimum of 48 mV at a current density of 10 mA?cm^-2in alkaline conditions,showing catalytic activity comparable to that of commercial Pt/C catalysts.In the first chapter,MoO₃ nanobelts were in situ grown on the carbon cloth by solvothermal method.At the same time,Ce?OH?₃ film was electrodeposited on the surface of the MoO₃ nanobelts and was subjected to high temperature phosphating to prepare Ce and P co-doped CePO₄/MoP/CC three-dimensional self-supporting HER electrode materials,which exhibits similar catalytic activity to commercial Pt/C in 1.0M KOH solution.Theoretical calculations reveal that modification of CePO₄ molecules not only increases interface synergy and promotes charge transport,but also optimizes the hydrogen adsorption energy,and thus greatly improving the HER performance of MoP.In the second chapter,we constructed a three-interface structure of RuP/CePO₄/MoP/CC via introducing Ru into the above CePO₄/MoP/CC electrodes on the basis of the first part of the work to further improve the HER performance.The phase structure,morphology,elemental composition,valence state,and charge transport properties were systematically studied.The results showed that this three-interface structure provides more channels for the rapid transfer of electrons and enhances the synergy between the three components.The electrocatalyst under its optimized conditions requires an over-potential of 29 mV to achieve a current density of 10 mA?cm^-2,even better than commercial Pt/C.In the third chapter,in order to further improve the stability and and applicability of the above obtained CePO₄/MoP/CC electrodes in a wide pH range,a nitrogen-doped carbon layer was introduced to be wrapped on CePO₄/MoP/CC to generate the CN@CePO₄/MoP/CC.The carbon layer not only can protect electrodes from morphological collapse during the electrodeposition and high-temperature phosphating processes,but also can provide more exposed active sites.Moreover,the doping of nitrogen atoms enhances the synergistic catalysis.Therefore,the electrode has excellent catalytic performance in a wide pH range,and the degradation of the catalyst performance after48 h is negligible.