From Behavior to Dynamics: Decoding Carrier Roles in Cu‐based Photocathodes for Solar‐Driven CO ₂ Reduction

Cu‐based photocathodes offer unique advantages for photoelectrochemical CO 2 reduction (PEC CO 2 RR) due to their earth abundance, tunable electronic structures and capacity to efficiently produce multi‐carbon (C 2+ ) products. However, their practical performance is fundamentally governed by the dynamics of photogenerated charge carriers, whose generation, separation, accumulation, transport, and extraction directly determine both catalytic efficiency and stability. This review examines how carrier behavior governs key reaction steps, evaluates material design strategies for tuning interfacial charge dynamics, and summarizes emerging techniques for probing these dynamics and interfacial transformations in operando. Looking ahead, integrating precise carrier control with stability and selectivity will be critical, requiring deeper insights into the coupling between carrier physics and catalytic function to guide the development of next‐generation Cu‐based photocathodes for PEC CO 2 RR.