Effect Of High-pressure Torsion On The Electrochemical Hydrogen Production Catalytic Properties Of Amorphous Alloys

Hydrogen is a clean energy carrier which is expected to replace fossil energy.Electrochemical water splitting is a sustainable way to produce hydrogen.However,this method still has great challenges in large-scale application due to its low energy conversion efficiency.Hydrogen evolution reaction（HER）is a key step in the production of hydrogen by electrochemical water splitting,and an efficient hydrogen evolution catalyst is required to improve the reaction efficiency and reduce the energy consumption of the reaction.Although Pt group metals exhibit high intrinsic catalytic activity for HER,but they are expensive and scarce in reserves.Therefore,the development of noble metal-free,highly activity and long-lived HER catalyst materials holds very important theoretical and application value.Amorphous alloys are metastable metal materials with long-range disordered atomic arrangement.Due to their abundant active sites,highly tunable composition,and easy preparation,amorphous alloys have been widely studied as catalyst materials in recent years.Despite the above advantages,the HER catalytic activity of amorphous alloys is still highly dependent on the composition of noble metal elements.Therefore,structural modification of amorphous alloy materials to improve their HER catalytic performance is of great significance.High-pressure torsion（HPT）is a method of severe plastic deformation（SPD）of materials,which can be used for alloying,grain refinement and other directions.In this study,a series of Fe-based and Pd-based amorphous alloys were treated by HPT.By introducing nano-scale defects into amorphous alloys and regulating the flow unit density in the amorphous matrix,the HER catalytic performance of the amorphous alloy is effectively improved.The specific research contents are as follows:In the first part of this work,we studied the effect of HPT treatment on Fe_73.5Si_13.5B₉Cu₁Nb₃amorphous alloy.The selection of this composition is based on our group’s previous research on Fe₇₈Si₉B₁₃ amorphous alloy.Adding Cu and Nb elements based on Fe-Si-B improves the glass-forming ability of amorphous alloys,and Cu and Nb elements are beneficial to some catalytic reactions,such as dye degradation.The study shows that the HPT treatment with different parameters reduces the overpotential of Fe_73.5Si_13.5B₉Cu₁Nb₃amorphous alloy in HER catalytic,and the HPT-5N sample with the best performance that the overpotential at 10 m A cm^-2 decreased from 418 m V to 174 m V.And it also decreased after 1000CV cycles which indicated the self-stabilization character of amorphous alloy.In the second part of this study,we prepared a Fe₇₅B₂₅ amorphous alloy.The results show that Fe element is the main active atom in HER catalysis,and the overpotentials of Fe₇₅B₂₅ amorphous alloy has a significant decrease after HPT treatment.The overpotentials corresponding to the 10m A cm^-2 current density of the HPT-1N,HPT-5N and HPT-10N samples have decreased from 402m V that of the original ribbon to 154 m V,139 m V and 116 m V,respectively.In addition,the Fe₇₅B₂₅ amorphous alloy has a lifetime of at least 300 hours both before and after HPT treatment,while the activity and stability of the HPT samples are much superior than the amorphous ribbon.In the first two parts of the study,it was found that Fe-based amorphous alloys were crystallized to a certain extent after HPT treatment.In the third part of this study,a Pd₄₀Cu₃₀Ni₁₀P₂₀amorphous alloy with low hardness and well toughness was subjected to HPT treatment and its HER performance were investigated.The Pd-based amorphous ribbons did not crystallize after HPT treatment,and their overpotentials of HER in both alkaline and acidic electrolytes were greatly reduced:The overpotential corresponding to the current density of 10 m A cm^-2 was decreased from 379 m V to 209 m V in 1 M KOH and from 179 m V to 76 m V in 0.5 M H₂SO₄.This proves that HPT treatment can effectively improve the HER catalytic performance of amorphous alloys without causing crystallization.The effect of HPT treatment on the atomic energy state of amorphous alloys was studied by DSC tests,and it was found that the density of flow units in the amorphous matrix was greatly increased after HPT treatment,which explained the reason for the improved HER performance from the atomic scale.