Phase engineering of iron group transition metal selenides for water splitting

Water splitting is an essential process for renewable energy systems, requiring efficient, economical, and abundant catalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Phase engineering of nanomaterials (PENs) has emerged as a promising strategy to optimize catalytic activity. Unconventional phases have been discovered in various nanomaterials, including metals, metal oxides, transition metal phosphides, and chalcogenides, making PENs a viable approach to catalyst design. The corresponding catalysts have exhibited distinctive HER and OER performances. However, the phase engineering of the iron group transition metal selenides (IGTMSes) for water splitting is still under development and needs systematic summarization. To assist researchers in understanding the trends in controllable phase engineering of IGTMSes for water splitting, this review provides detailed explanations of various PEN methods and traditional phase transition strategies.