中文摘要：

氢能是一种高热值、无污染的洁净能源.电解水制氢被认为是一种有效利用可再生能源,如风能、太阳能等,实现能量储存和转换的前沿科技.二维材料独特的结构和电子特性使其在催化电解水反应中具有广阔的应用前景.本文系统综述了二维材料在催化电解水反应中的两个半反应——阴极析氢反应（HER）和阳极析氧反应（OER）中的关键科学问题和最新进展,并展望了该领域所面临的挑战和机遇.

英文摘要：

Hydrogen is a kind of clean energy with high calorific value and non-pollution. There are many methods for hydrogen production. Fuel processing technologies transform a hydrogen containing material such as coal, petroleum, or natural gas into a hydrogen rich stream. However, these processes need an external heat source for the reactor and produce large amounts of carbon dioxide. Hydrogen production by electrolysis of water is regarded as an advanced technology to make effective use of renewable resources, such as wind power, solar power, etc., to achieve energy storage and conversion. Water electrolysis includes hydrogen evolution reaction（HER） and oxygen evolution reaction（OER）. These reactions are normally catalyzed by precious metals, such as platinum（Pt） and iridium（Ir）-based catalysts, which limits the large-scale application of electrolysis of water. Thus, it is necessary to develop alternative catalysts with low cost and high performance. Two-dimensional（2D） materials have considerable application prospect in electrocatalysis of H2 O because of their unique structural and electronic properties. In addition, 2D materials with a reduced dimension compared with the bulk material exhibits several distinctive properties, such as high specifc surface area, high thermal and electric conductivity and more catalytic active sites. In this review, the key scientific issues and the latest advances in the two half-reactions（HER and OER） of electrocatalytic water splitting with 2D materials are systematically summarized. The mechanisms of HER and OER are discussed briefly. The involved 2D materials for HER in this work include graphene, graphene encapsulated transition-metal catalysts, g-C_3N_4 and 2D transition-metal dichalcogenides, while for OER contain layered double hydroxide（LDH） and graphene encapsulated transition-metal catalysts materials. For graphene, g-C_3N_4 and 2D transition-metal dichalcogenides, there are various techniques to enhance the catalytic activity of the materials, s