Recent advances and perspectives on multicomponent metallic electrocatalysts for water splitting and related reactions.

Compositionally engineered metallic nanostructured catalysts have received burgeoning attention in electrochemical energy conversion. This growing interest stems from their tunable atomic structures, controlled stoichiometry, diverse coordination environments, enhanced orbital interactions, and high electronic and structural flexibility. Alloys are broadly classified into two categories: intermetallic compounds and solid-solutions based on their structure, phase and atomic arrangement. These structural characteristics play a pivotal role in determining electrochemical energy conversion performance. Consequently, compositionally engineered alloy nanostructures have emerged as promising candidates in this field. This review provides a detailed analysis of alloy-based electrocatalysts for energy conversion applications. We begin with a brief introduction to understanding hydrogen (H2) production, associated problems and potential solutions. This is followed by an overview of alloys, intermetallic compounds and solid solutions, with emphasis on their structure and compositional features. Subsequently, we summarize recent advances in alloy catalysts in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). To reduce the cell voltage and enhance energy efficiency, the OER has been potentially replaced by alternative oxidation reactions including the urea oxidation reaction (UOR) and hydrazine oxidation reaction (HzOR), particularly in contaminate degradation assisted energy conversion systems. In the following section, we discuss solid solution and intermetallic compound catalysts for the HER, OER, OWS, UOR, and HzOR. We further compile and analyze the relationship between catalyst electronic structures, catalytic activity and reaction kinetics, highlighting how electronic modulation influences these energy systems. As a conclusion, we provide a summary of key insights, current challenges and future research directions for the advanced compositionally engineered metallic electrocatalysts. We anticipate that this review will provide valuable guidance to early career researchers and contribute to advancing electrocatalyst design toward the industrialization of energy conversion technologies and the development of sustainable green energy economy.