In Situ Disentangling Local Thermal and Photoelectron Contribution in Photoelectrochemical Reactions Based on Optical Microfiber Sensors

The introduction of the photothermal effect holds significant importance for enhancing the efficiency of solar‐driven photoelectrochemical energy conversion, including water splitting, CO 2 reduction, and nitrogen reduction reactions. Distinguishing and quantifying the effects of local heating to photoelectrochemical reactions, however, remains challenging. Herein, it is reported that the local thermal in photoelectrochemical reaction can be in situ measured via an optical microfiber sensor, which captures thermo‐optic signals from highly sensitive modal interference. For proof‐of‐concept, the laser‐induced graphene (LIG) electrode as a model for photoelectrochemical reaction, which has emerged as a highly promising photoelectrode material owing its excellent photothermal conversion efficiency, tunable structure, and outstanding electrical conductivity. Experimental studies demonstrate that the local photothermal effects contribution can be quantified in real time, which further decoupling the photoelectronic effect contribution in photocurrent. Additionally, the potential for further enhancing sensitivity through dispersion turning point is demonstrated, achieving approximately five times the improvement over traditional fiber interferometers. This advancement holds promise for ultra‐sensitive detection of weak photoelectrochemical reactions. Therefore, this work provides critical experimental evidence for decoupling the photothermal and photoelectronic effects in photoelectrochemical reactions through a highly sensitive microfiber in situ detection technique, facilitating the development of advanced photoelectric materials and more efficient solar energy conversion systems.