This article reviews recent significant advances in the field of water splitting. Catalysts play very important roles in two half reactions of water splitting - water reduction and water oxidation. Considering potential future applications, catalysts made of cheap and earth abundant element(s) are especially important for economically viable energy conversion. This article focuses only on catalysts made of cobalt (Co), nickel (Ni) and iron (Fe) elements for water reduction and water oxidation. Different series of catalysts that can be applied in electrocatalytic and photocatalytic water spitting are discussed in detail and their catalytic mechanisms are introduced. Finally, the future outlook and perspective of catalysts made of earth abundant elements will be discussed.

A hybrid structure constructed by uniformly anchoring crystalline Ni ₂ P cocatalyst on 1D CdS nanorods exhibits extraordinarily efficient photocatalytic activity for H ₂ evolution in water (rate of 1,200 μmol h ⁻¹ mg ⁻¹ and TOF of 36,400 h ⁻¹ per mol Ni ₂ P) under visible light irradiation.