Controlled Electrodes Preparation Based On Non-thermal Radiation Heating And Study Of Electrocatalysis Activity Regulation

Hydrogen energy is considered as a renewable,environment-friendly,and clean energy.Electrolysis of water for production of hydrogen is a simple,clean,and efficient method,which has been applied in industry yield,but it required high energy consuming.In this regard,it is suggested that using renewable energies,such as solar and wind energy,provide electricity.On the other hand,preparing efficient electrocatalysts is also available to lower overpotential,thus lowering energy consuming.Pt-group noble metal whose free energy for hydrogen absorption are close to zero perform the most outstanding HER activity,but they are high price and their stability are poor.Traditional metal compounds such as MoS₂ and Mo₂C are inexpensive,which have comparable performance to noble-metal electrocatalysts.Traditional metal catalysts are usually prepared using radiation heating method such as hydrothermal and calcination method.To be specific,radiation heating is defined as that the heating of hot resistance wires is transferred to electrode by mediums.The radiation heating is an overall heating process where the electrode is not only heated,but also its surroundings are heated.Synthetic method has a direct impact on electrodes structure,which further impacts their electrocatalytic activity.Non-thermal radiation heating method can offset deficiency of radiation heating.It enables rapid heating and cooling rate,which is conducive to formation of defective structure to further endow outstanding electrocatalytic activity.In this basis,non-thermal radiation heating for preparing electrodes is studied in this article.We define non-thermal radiation heating as that electrodes themselves are heated and there is no need for an additional medium to transfer heat,which is a local heating process.Non-thermal radiation heating includes microwave heating,induction heating,Joule heating,laser heating,and electron beam heating.In this article,applying induction heating（IH）to prepare electrodes for electrolysis of water are mainly studied.The detailed research contents are as follows:1.With the electroxidation exfoliation graphite paper（ECP）used as both substrate and self-heated medium,the Ru（Ru/ECP）and RuO₂（RuO₂/ECP-IH）nanoparticles loaded on ECP are prepared by IH at Ar and air atmosphere,respectively.In acid electrolyte,the Ru/ECP and RuO₂/ECP-IH can achieve HER and OER with a overpotential of 117 mV and 197 mV at 10mA cm^-2,respectively.In alkaline electrolyte,the Ru/ECP and RuO₂/ECP-IH can achieve HER and OER with a overpotential of 50 mV and 277 mV at 10 mA cm^-2,respectively.Moreover,combining Ru/ECP and RuO₂/ECP-IH to assembly a two-electrode electrolyzer,the water splitting voltages of 1.6 V and 1.654 V are required to obtain 20 mA cm^-2 at acid and alkaline electrolytes,respectively.The voltages are lower than those of two-electrode electrolyzer constructed by commercial 20 wt%Pt/C and RuO₂.This result provides an available method for simple synthesis of electrodes applied in acid and alkaline water splitting.2.To expand applications of IH,the Ni foam with excellent conductivity,high specific surface area,and good flexibility is selected as self-heating medium and substrate.Various electrocatalysts including metal hydroxide and metal nitrides are grown on Ni foam by induction heating method and are applied in HER,OER,and ORR.Among them,the as-synthesized Ni-MoO₂ heterostructure and Ni Fe layered double-metal hydroxides（NiFe LDH/NF-IH）display excellent HER(-39 mV at 10 mA cm^-2)and OER(246 mV at 10 mA cm^-2)activity,respectively.Moreover,when the Ni-MoO₂/NF-IH and Ni Fe LDH/NF-IH are combined to construct electrolyzer for electrolysis of water,just potential of 1.5 V is required to achieve current density of 10 m A cm^-2.Besides,the as-synthesized Pt nanoparticles loaded on Ni foam by induction heating exhibits excellent HER and ORR activity.