Noble metal-free two dimensional carbon-based electrocatalysts for water splitting

Noble metal materials are widely employed as benchmark electrocatalysts to achieve electrochemical water splitting which comprises of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, the high cost and scarcity limit the wide ranging commercial applications of noble metal-based catalysts. Development of noble metal-free two dimensional (2D) carbon-based materials can not only reduce the consumption of noble metals, but also create materials with the characteristics of high active surface area, abundance, easy functionalization, and chemical stability, which may carve a way to promising electrochemical water splitting. In this review, noble metal-free 2D carbon-based electrocatalysts, including heteroatom (B, S, N, P, F, and O) doped graphene, 2D porous carbons modified with heteroatoms and/or transition metals, and 2D carbon-based hybrids are introduced as cost-effective alternatives to the noble metal-based electrocatalysts with comparable efficiencies to conduct HER, OER, and overall water splitting. This review emphasizes on current development in synthetic strategies and structure–property relationships of noble metal-free 2D carbon-based electrocatalysts, together with major challenges and perspectives of noble metal-free 2D carbon-based electrocatalysts for further electrochemical applications.