Non-Covalent Coupling of Carbon Nitrides and Dyes for Selective and Sensitive Electrochemiluminescent Detection of Local H+ in Oxygen Evolution Reaction

An accurate understanding of the mechanism of the oxygen evolution reaction (OER) is crucial for the design of efficient catalysts and the development of hydrogen energy. Despite significant advancements in microscopic pH detection studies through the use of mainstream strategies, such as scanning electrochemical microscopy (SECM), rotating ring-disc electrode (RRDE), and spectroscopic techniques, selective and sensitive detection of the change of proton (H+) concentration near the vicinity of the electrode during OER with high temporal resolution remains elusive. In this study, we pioneered the creation of an efficient hybrid electrochemiluminescence-based (ECL-based) pH sensor that enables the detection of H+ in the vicinity of the electrodes during OER. A new class of luminophore based on ECL resonance energy transfer (ECL-RET) was theoretically predicted and further synthesized by grafting fluorescent dyes onto carbon nitride nanosheets (CN) through non-covalent interaction. We present that one of the newly synthesized emitters, CN-FITC, is capable of detecting proton with fast response time, where the ECL intensity of CN-FITC is regulated by proton concentration. By coating this emitter onto an electrode positioned near OER catalysts, proton generation near the vicinity of the catalysts could be qualitatively detected, providing details of the reaction mechanism of OER and unveiling the catalyst degrading pathway caused by proton accumulation. Additionally, the average proton generation rate on the catalyst was extracted from the local pH measurement, leading to a quantitative descriptor of the OER reaction rate. Owing to the high designability of the dye, this study opens up a new strategy for the detection of more reaction intermediates.