• Carbon-based transition metal catalysts combine high activity and stability, offering a cost-effective alternative to precious metals for the hydrogen evolution reaction (HER).
• The carbon component's role extends beyond a conductive support; it actively modulates the electronic structure via heteroatom doping, enhancing intrinsic catalytic activity.
• Morphology adjustment of carbon materials increases the number of active sites and improves mass transport, boosting apparent catalytic performance.
• Self-supporting carbon architectures eliminate the need for binders, improving electrode stability and facilitating practical application in water splitting.