炭纸衬底上化学气相沉积直立型二维过渡金属硫化物及其电催化产氢性能

Chemical vapor deposition of two-dimensional transition metal sulfides on carbon paper for electrocatalytic hydrogen evolution

以MoS_(2)为代表的二维过渡金属硫化物近年来在电催化水分解产氢反应中表现出良好的电催化活性而受到广泛关注。但二维过渡金属硫化物的导电性一般较差、且催化活性位常在有限的边缘位置,成为限制其催化性能的重要因素。本文通过化学气相沉积方法研究了在炭纸基底上直接生长3种过渡金属硫化物(MoS_(2)、NbS_(2)和WS_(2))构筑一体化催化电极,以提高整个电极的导电性。通过优化生长工艺,实现了炭纸表面3种过渡金属硫化物的直立型生长并对电催化产氢反应表现出良好的催化性能,尤其是WS_(2)表现出新颖的纳米片/纳米纤维层次结构,其对产氢反应表现出最佳的催化性能。在此基础上,对炭纸上生长的过渡金属硫化物通过阴极电化学活化处理的方式引入硫缺陷,从而提高其HER活性。结合透射电子显微镜和原位电化学拉曼光谱仪研究了二维过渡金属硫化物在电化学活化前后的结构变化尤其是所产生的硫缺陷的微观结构,为其产氢性能的提升提供合理的解释。

Hydrogen is considered the most likely alternative clean energy fuel to traditional fossil fuels.One of the most attractive hydrogen production strategies is water splitting,but the need for expensive Pt precious metal catalysts to catalyze the hydrogen evolution reaction(HER)is a problem.Recently,two-dimensional transition metal dichalcogenides(TMDs),especially MoS_(2),have attracted intense interest as a non-precious metal HER catalyst due to their low cost and relatively high catalytic activity.However,their poor electron conductivity and the limited number of active sites at their edges have greatly limited their overall catalytic performance.We report the direct growth of three representative TMDs(MoS_(2),NbS_(2) and WS_(2))on a conductive carbon paper substrate using chemical vapor deposition and have studied the effects of temperature and gas flow rate on their morphology and structure.All the as-grown TMDs have a 2D nanosheet morphology and were aligned perpendicular to the carbon paper.The WS_(2) nanosheets had the smallest sheet size with a diameter of ca.100-200 nm and,more interestingly,were assembled into a one-dimensional nanofiber,leading to the highest HER activity.Additional electrochemical cathodic activation further improved the HER activity of the TMDs,and the structural changes after the activation were investigated by TEM combined with in-situ electrochemical Raman spectroscopy.The activated NbS_(2) contained large triangular or truncated triangular S vacancy areas,which is distinctly different from the individual S vacancies in MoS_(2).