Sustainable carbon-based composites for hydrogen evolution: catalyst engineering and performance enhancement pathways

Achieving carbon neutrality by 2050 is a central global objective that is accelerating the transition to sustainable hydrogen. Water electrolysis, particularly the hydrogen evolution reaction (HER), offers a promising pathway for clean hydrogen production. Nonetheless, high catalyst cost, limited durability, and sluggish alkaline kinetics remain significant obstacles. This review systematically examines the design and application of carbon-based composite catalysts for HER, spanning carbon-based materials and electrodes to hydrogen production devices and, ultimately, the broader hydrogen energy system. We also outline upgrade pathways for hydrogen production devices and optimization strategies for the hydrogen energy system, with particular attention to China's growing energy demand and continued dependence on fossil fuels. We analyze advanced structural strategies, including transition-metal doping (e.g., iron, cobalt, and nickel), heteroatom modification (e.g., nitrogen-doped graphene), and hierarchical architectures (e.g., three-dimensional porous frameworks and single-atom catalysts). The latest progress in the development and optimization of catalyst materials was summarized, with an emphasis on methods to improve catalytic activity and stability. We compare the advantages and disadvantages of four electrolyzer types. In addition, we provide an overview of the global hydrogen landscape, with emphasis on China's progress in hydrogen production, storage, and utilization. This review highlights the roles of heteroatom doping, active-site engineering, and synergy between the electrolyte and the catalyst in improving HER performance. We examine the effects of temperature management and flow-channel design on hydrogen production devices within integrated systems that leverage artificial intelligence and multi-energy coupling. Finally, we discuss current limitations of water electrolysis for hydrogen production and outline future directions, including improving catalyst robustness under complex conditions, reducing production costs, simplifying synthesis methods, upgrading the design of existing hydrogen production devices, adopting interdisciplinary approaches for mechanism analysis, integrating artificial intelligence with regional, large-scale hydrogen energy systems, and reducing avoidable hydrogen energy losses to improve efficiency. These insights aim to advance water electrolysis technology, support the global carbon-neutrality goal, and guide future research on sustainable hydrogen production. Compared with previous reviews that mainly focus on catalyst synthesis and intrinsic activity, this work uniquely bridges carbon-based catalyst design with electrode engineering, electrolyzer technologies, and hydrogen energy systems, providing a unified framework to accelerate the development of efficient, durable, and scalable hydrogen production for global carbon-neutrality goals.