Tracing the Origin of Driving Force of Photoinduced Interfacial Electron Transfer Reaction by Colocated Scanning Electrochemical Microscopy

Solar energy is the ultimate power source for mass and energy conversions on this planet through photochemical reactions. Among these, photoinduced interfacial electron transfer (PIET) reactions are driven by photofield-induced Volta potentials, fundamentally different from classical electrochemical processes by directly applied potential through a potentiostat. Herein, we develop a colocated scanning electrochemical microscopy (SECM) approach─integrating with atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM)─to correlate the morphology, Volta potential, and PIET kinetics at the same located silver sheet/single-layer graphene (Ag/SLG) electrode. We reveal that illumination induces π-π* transitions in SLG and d-electron excitations in Ag, leading to a synchronous positive shift of the Fermi level of the Ag/SLG electrode, acting effectively as a photogenerated interfacial potential. More importantly, the Volta potential difference across the Ag/SLG boundary, determined by their electron work function, remains nearly constant. The synergy between the photoinduced Volta potential and the Volta potential difference across the Ag/SLG boundary underpins the enhanced PIET efficiency. This study provides a direct methodology to quantify physical-field-driven interfacial electron transfer and establishes a framework for the rational design of catalyst/carrier systems beyond conventional electrochemical paradigms.