Design Of Pd/Ru-based Nanocatalysts And Their Study In Electrocatalytic Alcohol Oxidation And Water Splitting

Energy and environment have always been a global hot issue,and with the extremely rapid development of China’s economy,the problem of environmental pollution caused by excessive consumption of non-renewable energy sources has become increasingly serious.The development of efficient,green and pollution-free energy production technologies is the key to solving energy scarcity and environmental pollution.And electrocatalysis,as a highly efficient energy storage conversion technology,has the ability to convert organic small molecules or water into green,non-polluting,human-friendly products（e.g.carboxylic acids,esters,oxygen and hydrogen）,opening up a new path to solve the existing fuel depletion and environmental pollution problems caused by non-renewable energy consumption.However,the method generally suffers from slow reaction kinetics and high operating voltages.Therefore,highly active,selective and stable electrocatalysts need to be prepared in order to increase the reaction efficiency.At present,precious metal-based materials remain one of the best performing catalysts in the field of electrocatalysis,facilitating the reduction of the activation energy of electrocatalytic reactions and providing conduction sites for electrochemical reactions,thereby increasing the rate of the reaction.However,due to their scarcity and high cost,precious metal-based catalysts need to be rationally designed to reduce their usage and improve their performance.In this paper,a range of synthetic methods are used to design the catalysts through a number of different modulation methods,the main ones being as follows.1.A series of Pd Cu/CNT nanocatalysts with face-centred cubic（fcc）and body-centred cubic（bcc）phases were prepared by synthesising Pd Cu nanoparticles in an oil bath and then loaded onto carbon nanotubes using an alloying and crystallographic phase control design approach,and its application in alkaline ethanol oxidation was investigated.The Pd Cu/CNT nanoparticles produced fcc crystalline phase,bcc crystalline phase and a mixture of fcc and bcc crystalline phases at different calcination temperatures.At a calcination temperature of 300℃,the Pd Cu/CNT-300 catalysts showed a mixed fcc:bcc=2:1 crystalline phase with the highest electrocatalytic activity for ethanol oxidation:mass activity reaches 7.8 A mg _Pd^-1 and area activity reaches 17.0 m A cm^-2,with good electrochemical stability and structural stability.In addition,the selectivity of the C1 pathway can reach 53.9%.This excellent performance is attributed to the enhanced electron donor activity of Pd by Cu,achieving a synergistic effect between the bimetals,and the phase interface brought about by the mixed crystalline phases,which together modulate the electronic structure of the catalyst and increase the electron transfer rate of the catalyst.Ultimately,the CO anti-toxicity of the catalyst was improved and the C-C bond-breaking ability of the catalyst was enhanced,which in turn improved the selectivity and catalytic oxidation activity of the C1 pathway of ethanol in alkaline media.2.A series of M-Ru/Ru O₂@CNT（M=Mn,Cd,Cu）bifunctional catalysts were designed and synthesised by doping and strong metal-support interaction（SMSI）to improve the activity and stability of the catalysts.A simple,efficient and solvent-free microwave pyrolysis method was used and the whole reaction process required only180 s.The synthesised Mn-Ru/Ru O₂@CNT catalysts with ultra-small particle size（2.5nm）exhibited the best catalytic performance,with oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）tests showing excellent overpotentials of 177m V and 30 m V,respectively,in 0.5 M H₂SO₄ solution at a current density of 10 m A cm^-2.In addition,current densities of 10 m A cm^-2 and 100 m A cm^-2 were obtained at1.43 V and 1.51 V,respectively,when measuring water splitting,and were maintained at a current density of 100 m A cm^-2 for 100 h.This is the first time that a Ru-based catalyst has been able to perform stable acidic water splitting at high current densities.Density functional theory（DFT）shows that Mn doping improves the catalytic activity by changing the electronic structure and optimising the binding energy of the intermediates through charge redistribution between the dopant ions and the ruthenium-based catalyst containing heterojunctions,and improves the stability of the catalyst by increasing the formation energy of ruthenium vacancies and preventing the formation of ruthenium vacancies.