Recent advances and future research directions in polyoxometalate-based water electrolysis for hydrogen production

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.