Fabrication of Earth-Abundant Electrocatalysts Based on Green-Chemistry Approaches to Achieve Efficient Alkaline Water Splitting—A Review

The fabrication of earth-abundant electrocatalysts by green-chemistry approaches for electrochemical water splitting could diminish or alleviate the use or generation of hazardous substances, which could be highly desirable to achieve efficient, green alkaline water electrolysis for clean energy production (H2). This review started by introducing the importance of the green-chemistry approaches. Later, this paper reviewed the fabrication of high-performance earth-abundant electrocatalysts using green-chemistry approaches for electrochemical water splitting (HER and OER). Moreover, this review discussed the green-chemistry approaches for the fabrication of earth-abundant electrocatalysts including phosphide/pyrophosphate-, carbon-, oxide-, OH/OOH/LDH-, alloy/B/nitride-, and sulfide/selenide (chalcogenide)-based earth-abundant electrocatalysts. Moreover, this review discussed various green-chemistry approaches, including those used to alleviate toxic PH3 gas emission during the fabrication of transition-metal phosphide-based electrocatalysts, to design energy-efficient synthesis routes (especially room-temperature synthesis), to utilize cheap or biodegradable substrates, and to utilize biomass waste or biomass or biodegradable materials as carbon sources for the fabrication of earth-abundant electrocatalysts. Thus, the construction of earth-abundant electrocatalysts by green-chemistry approaches for electrochemical water splitting could pave an efficient, green way for H2 production.