Plasma Mediated Preparation Of Transition Metal-based Catalysts And Its Performance In Electrocatalytic Oxygen Evolution Reaction

The growing global energy and environmental problems have created an urgent need to develop renewable and clean energy sources,and hydrogen energy is considered the cleanest fuel and a promising alternative to fossil fuels.In recent years,the electrolysis water technology has won much focus for producing high purity hydrogen in an eco-friendly and sustainable manner.However,the anodic oxygen evolution reaction（OER）exhibited sluggish kinetics in four electron transfer processes.The overpotential of OER can be substantially reduced with noble metal-based catalysts such as Ru O₂and Ir O₂,but their scarcity and high cost raise the cost of hydrogen production.Therefore,developing high-efficient and cheap non-precious metal-based electrode materials to reduce the cost of hydrogen production,this is one of the key points that the development of new energy strategies with electrocatalysis as the core.At present,plasma technology exhibits great advantages in material synthesis and surface modification.In this work,NiFeN_xnanoparticles（NiFeN_x/NF）were synthesized on nickel foam by plasma technique,Fe₃O₄/NF was etched by plasma,Fe,Co and Ni-based hydroxides（M（Fe,Co,Ni）-OH）were post-treated by plasma technique,nitrogen-doped carbon by nitrogen plasma,and study their performance in electrocatalytic OER.The main contents are as follows:（1）NiFeN_x/NF material was synthesized by hydrogen and nitrogen plasma and studied its OER performance.Firstly,the plasma method does not cause pollutants during the preparation of transition metal nitrides,which is different from the conventional solvent thermal method and NH₃nitridation method;Secondly,the NiFeN_xnanoparticles are uniformly distributed on the NF surface,which makes the active sites well-exposed;Finally,Due to the synergistic effect between NiFeN and Ni₂Fe₂N,NiFeN_x/NF can substantially reduce the OER overpotential.（2）The catalytic performance of Fe₃O₄/NF was further enhanced by using argon plasma etching.This plasma etching treatment improves the catalyst performance problem,which is caused by particle aggregation on the catalyst surface.p-Fe₃O₄/NF has higher electrocatalytic OER performance than Fe₃O₄/NF,which is mainly attributed to the large specific surface area of p-Fe₃O₄/NF,allowing more active sites to contact with the electrolyte.（3）M（M=Fe,Co,Ni）-OH/NF post-treated with nitrogen,hydrogen,and oxygen plasma.electrocatalytic OER test results showed that the electrocatalytic OER performance of Fe（OH）₃/NF was better than that of Co（OH）₂/NF and far exceeded that of Ni（OH）₂/NF;The lower content of Fe in Fe_xCo_y（OH）_z/NF can significantly enhance its OER performance.The OER test results showed that the nitrogen plasma post-treatment could not enhance the catalytic performance of Fe（OH）₃/NF at different temperatures,which may be caused by the larger size of nanoparticles on the Fe（OH）₃/NF-x surface.and in addition,hydrogen and oxygen plasma could not enhance the OER performance of Fe（OH）₃/NF.However,it is interesting that nitrogen plasma can significantly enhance the OER performance of Fe_0.5Co_0.5（OH）_x/NF and oxygen plasma can enhance the OER performance of Ni（OH）₂/NF.（4）Carbon black was doped using nitrogen plasma.XPS results showed that the nitrogen plasma was enabled to perform nitrogen doping up to～7%in only 10 min with the highest pyridine nitrogen content.The OER test results showed that the OER performance of N/C materials was positively correlated with the content of pyridine nitrogen.In addition,we prepared M-N/C（Fe,Co,Ni）by impregnation method,and the results of electrocatalytic OER test showed that Fe-N/C outperformed Co-N/C and Ni-N/C in terms of OER performance.Moreover,due to the synergistic effect of bimetals,Fe-Ni-N/C outperformed the monometallic catalyst Fe-N/C in OER performance.