Preparation Of Ru-based Electrocatalysts For Oxygen Evolution Reaction By Magnetron Sputtering

With the rapid development of economy,the chemical energy stored in the earth is rapidly consumed,resulting in a serious energy crisis and environmental pollution.As a clean,green and high-density energy source,hydrogen energy is currently the preferred alternative energy source.Among all the present methods of producing hydrogen,electrolyzing water is one of the most promising method.In the process,it consumes water,and products hydrogen and oxygen.So it is environmentally friendly.In the process of hydrogen production,it is necessary to consider not only the hydrogen production process,but also the oxygen evolution reaction?OER?which is a semi-reaction of electrolyzing water.However,OER,as a four-electron reaction,has a high kinetic barrier,which has lead to very large impact.Therefore,it is necessary to study a suitable OER catalyst.At present,ruthenium-based catalysts have high activity and are the most important OER catalysts of the commercial electrodes.However,the commercial RuO₂ catalyst still needs 420 mV overpotential at a current density of 10 mA·cm^-2,which needs to be further reduced.Therefore,this paper aims to study how to use the ruthenium-based materials more efficiently to obtain better OER activity.Different preparation methods of magnetron sputtering and doping of non-precious metals Fe and Co were mainly the studied.The main research contents are as follows:?1?Different RuO₂ catalysts were prepared by magnetron sputtering technique.Under RF oxygen sputtering,RuO₂-R?O?catalyst has relatively high OER activity,and its activity is 1.285 A·mg^-1 at 1.8 V?vs.RHE?potential,compared to DC sputtering of RuO₂-D?O?catalyst(1.113 mA·mg^-1),increased by 15%.At the same time,it was increased by 25%compared to the RuO₂-T catalyst(1.027 mA·mg^-1)prepared by thermal decomposition.The Tafel slope of the RuO₂-R?O?catalyst is 68.8mV·dec^-1,indicating that the reaction S-OH*_ads+OH^-S-O*_ads+H₂O is the rate controlling step.In addition,the effects of sputtering time,sputtering pressure,sputtering oxygen content and calcination temperature on the OER activity of RuO₂-R?O?catalyst were also investigated.?2?Fe-doped RuO₂ catalyst was prepared by magnetron co-sputtering.Fe doping significantly increases the OER activity of the RuO₂ catalyst,requiring only an overpotential of 312 mV at a current density of 10 mA·cm^-2,which is 44 mV lower than that of the RuO₂ catalyst?356 mV?.At the same time,the Tafel slope of Fe-doped RuO₂ catalyst is 56.6 mV·dec^-1,indicating that Fe doping promotes the formation and conversion efficiency of O_ads intermediate in RuO₂.At the same time,the amount of Fe doping affects the OER activity of the catalyst.When the Fe doping amount is 25%,the obtained RuO₂-Fe?25?-400 catalyst has an optimum OER catalytic activity.Its current density at a potential of 1.6 V was 32.41 mA·cm^-2,which was about 2.6 times that of the RuO₂ catalyst(12.46 mA·cm^-2).?3?First,a RuCo alloy was prepared by magnetron co-sputtering,and then the Co-doped Ru-based catalyst was prepared by the CV de-alloying process.The CV scan dissolves Co in the RuCo alloy catalyst,thereby increasing the electrochemical area ofthe catalyst and significantly increasing the OER activity of the catalyst.The current density of the catalyst at a potential of 1.8 V was 125.40 mA?cm^-2,which was1.34 times higher than that of the RuCo catalyst before demetalation(53.55 mA?cm^-2);compared to the Ru catalyst(68.06 mA?cm^-2),increased by about 1 time.In addition,the effects of Co content in the catalyst,the number of CV segments during de-alloying and the type of electrolyte on OER activity were also discussed.Among them,the longer CV segment number and higher pH electrolyte are beneficial to obtain high activity and stability OER catalyst;while Co content has little effect on its activity.