Emerging two-dimensional nanomaterials for electrochemical hydrogen evolution

Hydrogen has been verified as a clean and economical energy source, due to its high mass energy density and renewability. Electrochemical water splitting is regarded as one of the most economical and eco-friendly approaches for hydrogen evolution. Recently, emerging two-dimensional (2D) nanomaterials have demonstrated their potential as distinguished non-noble catalysts for hydrogen evolution. These ultrathin nanomaterials are dramatically different from their bulk counterparts. Abundant active sites are maximally exposed and the small diffusion paths of the ultrathin nanosheets can effectively facilitate charge transfer in the electrocatalytic hydrogen evolution. Moreover, many tactics can be easily adopted in such an interesting and adjustable platform, which makes the 2D material an ideal object to explore the exciting catalytic activity and electronic transfer. Various inventive strategies regarding increasing active sites, improving intrinsic activity and enhancing electrical conductivity for enhancing catalytic performance are urgently pursued. Here, the primary criteria for evaluating catalysts in electrochemical HER is discussed, followed by a brief introduction of the superiorities of 2D nanomaterial catalysts for HER. Based on these, recent strategies for improving the catalytic activity of 2D nanomaterials are summarized. We believe this review will provide deep insights for understanding the 2D material catalysts for catalyzing HER, and aid in devising new catalysts with high catalytic activity.