Carbon dots in photocatalytic water splitting and related proton/electron‐coupled reactions: Multiscale regulation of charge dynamics and interfacial processes

Abstract Photocatalytic water splitting provides a representative platform for understanding the relationship between photogenerated charge utilization and interfacial catalytic conversion. The overall efficiency of this process is governed by the coupling between ultrafast photophysical events and slower interfacial redox reactions. Carbon dots (CDs), with tunable carbon‐core structures, surface functional groups, defect states, dopant sites, and flexible interfacial chemistry, are well suited for regulating such multiscale charge‐reaction coupling. This review focuses on CD‐based photocatalytic water splitting and related proton/electron‐coupled reactions from the perspective of multiscale charge utilization. A spatiotemporal framework is first established to describe CD‐mediated charge evolution and its matching relationship with interfacial catalytic reactions. Recent regulation strategies for CD‐based systems are then summarized, including light‐harvesting modulation, carrier‐behavior regulation, interfacial charge transfer, and local reaction‐environment construction. Particular emphasis is placed on transient and operando characterization techniques that connect early‐stage charge dynamics with reaction‐relevant interfacial processes. The roles of theoretical calculations and emerging machine‐learning approaches in identifying structure‐property relationships, reaction descriptors, and charge‐utilization mechanisms are also discussed. Finally, current challenges and future opportunities are outlined, highlighting the need for mechanism‐oriented characterization, rational interfacial design, multiscale theoretical modeling, and data‐driven descriptors for efficient charge utilization in CD‐based photocatalytic systems.