Functional Nanoengineering of Catalytic Environments for High‐Efficiency Electrochemical Water Splitting

The development of highly efficient water-splitting technologies relies on the precise control of catalytic environments at the nanoscale, where structural, electronic, and interfacial properties collectively determine catalytic performance. Recent advances in nanoengineered electrocatalysts, including noble-metal nanostructures, single-atom catalysts, defect-rich oxides, heterointerface-engineered systems, and carbon-supported multidimensional architectures, have revealed new opportunities for tailoring catalytic nanoenvironments to enhance hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. This review highlights emerging strategies for engineering functional catalytic environments that regulate charge transfer, optimize active-site exposure, facilitate mass transport, and improve structural robustness under practical electrochemical conditions. Particular attention is given to ultrathin oxyhydroxide layers, vacancy-mediated surfaces, lattice-distorted phases, and multicomponent heterostructures that exhibit superior activity and long-term durability. In addition, recent progress in operando characterization, theoretical modeling, and integrated electrode design is discussed to elucidate structure-function relationships governing catalytic performance. Finally, scalable synthesis approaches, engineered porous electrodes, and data-driven catalyst discovery are examined as promising pathways toward practical implementation. By connecting nanoscale materials engineering with functional electrocatalytic performance, this review provides critical insights into the rational design of catalytic nanoenvironments for next-generation water-splitting technologies.