Identification and mechanistic understanding of active sites in bimetallic catalysts for electrochemical water splitting

Abstract

The development of efficient, durable, and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is central to advancing electrochemical water splitting as a scalable platform for green hydrogen production. Among emerging candidates, bimetallic catalysts offer exceptional promise due to their tunable electronic structure, synergistic surface interactions, and rich redox chemistry. This review critically examines the latest advances in identifying and elucidating the real active sites in bimetallic systems, highlighting their dynamic evolution under operating conditions and their influence on catalytic performance. We explore how structural motifs, including atomically dispersed dual sites, alloyed nanophases, heterointerface, and core–shell architectures, govern activity and stability by modulating adsorption energetics, charge transfer, and lattice strain. Emphasis is placed on integrating in situ and operando spectroscopic techniques with theoretical tools, such as density functional theory (DFT) and machine learning-assisted modeling, to uncover mechanistic pathways and establish accurate structure–activity relationships. Distinguishing geometric versus electronic contributions to active site behavior, with comparisons across acidic, alkaline, and saline media, is given particular attention. By bridging experimental observations and theoretical predictions, this review provides a comprehensive framework for the rational design of bimetallic electrocatalysts tailored for high-efficiency water splitting, offering insights into overcoming current limitations and guiding future directions in renewable hydrogen technologies.