Engineering of abundant metal complexes for electrochemical water splitting.

Advancements in water splitting technologies are crucial for achieving sustainable hydrogen production. Development of highly efficient and economically viable catalysts is essential for commercialization of water electrolysers. While precious metals like platinum and iridium are renowned for their catalytic capabilities in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), their high cost and scarcity present significant challenges. Hence, various metal oxides, carbides, sulfides, phosphides, alloys, metal complexes, and composites have been examined as potential catalysts for water splitting reactions. This review offers a comprehensive analysis of Earth-abundant metal complexes as promising alternatives for water splitting catalysis. The fundamental principles underlying water splitting, including electrochemical dynamics, thermodynamics, and reaction kinetics, and their impact on catalytic performance have been evaluated. Emphasis is placed on the pivotal role of Earth-abundant metals such as manganese, iron, cobalt, nickel, and molybdenum and their recent innovations in catalyst design focussing on composites for enhancing the HER, OER, and integrated dual-function catalysis are discussed. Comparative evaluation related to advantages and limitations of these alternatives with respect to precious catalysts in terms of cost, availability, and environmental impact is presented. To integrate the same catalyst for HER and OER activities, insights into strategies for optimization of the performance are provided. Additionally, the review highlights the contributions of computational chemistry, including density functional theory studies in engineering catalyst design and understanding reaction mechanisms. Finally, an assessment of current challenges and future directions is presented to provide a holistic perspective on the transformative potential of Earth-abundant metal complexes in advancing sustainable water splitting technologies.