Non-carbon-supported low-loading precious metals: from rational synthesis to mechanism insight for advanced electrocatalysis

Non-carbon-supported low-loading precious-metal (NCS-LLPM) electrocatalysts address the cost and scarcity bottlenecks inherent in precious metals through their ultralow loading, rendering scale-up economically viable. Their combined activity and durability meet device-level operational requirements and facilitate the laboratory-to-device transition toward industrial electrolyzers. Scaled deployment in clean electrochemical conversion curtails reliance on fossil-derived processes, offering a tangible route to emission reduction and sustainability. Rational design of non-carbon supports exploits their diverse bonding modes and coordination configurations with metal sites, which constitute structural degrees of freedom largely absent in conventional carbon supports. This bonding drives charge transfer and orbital hybridization, reshaping the electronic structure of the anchored metal and tightening the metal-support interaction. These reinforced interactions also suppress the oxidative corrosion and agglomeration that typically degrade carbon-supported catalysts, improving long-term operational stability. This review first summarizes typical synthetic routes and highlights advanced strategies including microwave-assisted fabrication and high-throughput screening. The role of non-carbon supports in regulating catalytic performance is examined in terms of electronic structure modulation, conductivity enhancement, and coordination-environment optimization. It further categorizes reported NCS-LLPM catalysts, including emerging single-atom systems, and summarizes recent advances across key energy conversion reactions, such as hydrogen evolution, oxygen evolution, oxygen reduction, nitrate reduction, alcohol oxidation, and carbon dioxide reduction. Analysis of inherent trade-offs across different support families reveals a set of general design principles and identifies dynamically adaptive metal-support interfaces as a unifying framework for achieving high performance. Finally, critical challenges in scalable synthesis and practical implementation are discussed, together with targeted optimization strategies and perspectives for future development.