Surface And Interfacial Engineering Of Transition-metal Chalcogenides Nanomaterials For Electrocatalysis

Eletrocatalytic technology has been widely developed as an effective approach to alleviate the ever-growing energy crisis and environmental problems.Therefore,it is highly necessary to pursue inexpensive electrocatalysts with high activity and stability in the field of energy conversion.Transition-metal materials have been regarded as promising alternatives to noble-metal catalysts due to their unique electronic structures,high abundance and low price.Among them,transition-metal chalcogenides have drawn great attention in the area of electrocatalysis because of their excellent electronic properties.However,their electrocatalytic performance is still quite low,far below the needs of practical applications.It should be noted that modulation of surface and interfacial structures of materials would have a significant influence on their electrocatalytic activity since catalytic reaction usually occurs on the surface sites of catalysts.Accordingly,we mainly focused on the regulation of surface and interfacial structures of transition-metal chalcogenides nanomaterials by heterointerface engineering and construction of amorphous structures,aiming to optimize the surface and electronic structures of electrocatalysts and eventually achieve enhanced electrocatalytic performance.Moreover,taking these catalysts as examples,we elucidated the inherent relationships between surface/interfacial structures and electrocatalytic activities via a combination of experimental investigations and theoretical calculations.The main contents are as follows:（1）With the aid of experimental and theoretical studies,the Cu₂O-Cu S heterostructure was constructed as a proof of concept to illustrate the role that heterojunctions play in the glucose sensing process.Density functional theory（DFT）calculations revealed that Cu₂O-Cu S heterojunctions possessed a decreased formation energy of electroactive Cu（III）species along with a lower adsorption energy of glucose molecules,enabling more favorable reaction kinetics for glucose electrooxidation.As expected,the Cu₂O–Cu S electrode shows superior electrochemical glucose sensing performance with respect to the Cu₂O electrode.This work provides significant implications for designing advanced electrochemical sensors in the future.（2）We highlight a facile microwave-assisted strategy to achieve the synthesis of amorphous and crystalline Ni S₂ nanospheres by governing their crystallinity with varying the type of sulfur source,and subsequently employ them as alternative catalysts for the electrochemical MOR.Notably,taking the amorphous and crystalline Ni S₂catalysts as a promising platform,the underlying relationship between amorphous structure and MOR performance is deeply investigated by means of the combination of theoretical simulations and experimental measurements.Benefiting from its condensed active sites and increased intrinsic reactivity as well as optimized reaction kinetics,the amorphous Ni S₂ catalyst possesses superior electrocatalytic MOR activity over the crystalline counterpart,affording a large current density of 200 m A cm^-2 at the potential of 0.6 V vs.Ag/Ag Cl,nearly 3 times higher than that of the crystalline one.This work can provide a guideline for the design and optimization of highly active MOR electrocatalysts.