Hydrogen energy, as a clean, efficient, and renewable secondary energy carrier, plays a pivotal role in the global energy transition and the achievement of "dual carbon" goals. Among the various hydrogen production pathways, water electrolysis has emerged as the most promising approach for green hydrogen generation owing to its zero carbon emissions during operation and the high purity of the hydrogen produced. However, conventional electrolysis technologies depend heavily on noble-metal catalysts, such as platinum and iridium oxide, whose high cost and limited abundance severely restrict large-scale industrial deployment. Therefore, the development of high-performance, durable, and cost-effective catalysts for water electrolysis remains a critical challenge for the advancement of hydrogen energy technologies. Polyoxometalates (POMs), a class of nanoscale metal–oxygen clusters composed of transition metals such as molybdenum and tungsten, have emerged as promising alternatives owing to their diverse redox states, molecular-level tunability, high negative charge density, and excellent structural stability. This review systematically elucidates the advantages of POM-based materials for both the hydrogen evolution reaction and the oxygen evolution reaction in water electrolysis. By integrating recent advances, it summarizes diverse strategies aimed at overcoming the current limitations of POM electrocatalysts. Finally, the review discusses the opportunities and challenges associated with using POM compounds to enhance water electrolysis performance for hydrogen production and, by synthesizing state-of-the-art research directions, and provides an outlook on future trends in this rapidly developing field.

Designing and synthesizing high-efficiency non-precious metal-based catalysts having uniform active sites increases the reactivity and selectivity of materials and provides a platform for an in-depth understanding of their catalytic reaction mechanism. In this study, we provided an approach for fabricating isolated nickel single-atom sites (Ni SAs) with high loading (4.9 wt.%) stabilized on nitrogen-doped hollow carbon spheres (NHCS) using a core–shell structured Zn/Ni bimetallic zeolitic imidazolate framework (ZIF) composite as the sacrificial template. The as-fabricated Ni SAs/NHCS catalyst shows superior activity, selectivity, and recycling durability for the catalytic transfer hydrogenation of nitrobenzene to aniline, thus achieving 100% yield of aniline with a turn-over frequency (TOF) value as high as 29.9 h⁻¹ under mild conditions. This TOF value is considerably superior to the supported Ni nanoparticle catalysts. The experiments designed show that the hollow structure feature of NHCS facilitates accessible active sites and mass transfer, which thus contributes to the enhancement of the catalytic performance of Ni SAs/NHCS. Density functional theory calculations show the high chemo-selectivity and activity of the Ni SAs catalyst, arising from the unique role of the single Ni-N₃ site on simultaneously activating the H donor (N₂H₄) and substrate, as well as the hydrogenation of the –NOH group as the rate-determining step.

Electrochemical nitrogen reduction reaction (NRR) under ambient conditions is highly desirable to achieve sustainable ammonia (NH₃) production via an alternative carbon free strategy. Single-atom catalysts (SACs) with super high atomic utilization and catalytic efficiency exhibit great potential for NRR. Herein, a high-performance NRR SAC is facilely prepared via a simple deposition method to anchor Au single atoms onto porous β-FeOOH nanotubes. The resulting Au-SA/FeOOH can efficiently drive NRR under ambient conditions, and the NH₃ yield reaches as high as 2,860 μg·h⁻¹·mg_Au⁻¹ at −0.4 V vs. reversible hydrogen electrode (RHE) with 14.2% faradaic efficiency, much superior to those of all the reported Au-based electrocatalysts. Systematic investigations demonstrate that the synergy of much enhanced N₂ adsorption, directional electron export, and mass transfer ability in Au-SA/FeOOH greatly contributes to the superior NRR activity. This work highlights a new insight into the design of high efficient NRR electrocatalysts by combination of porous metal oxide matrix and highly active single-atom sites.