Sequence-Controlled Electrochemical Immobilization of Catalyst-Photosensitizer Oligomers for Tuning Photoelectrochemical Behaviors

Immobilizing catalysts and photosensitizers on an electrode surface is crucial in interfacial energy conversion. However, their combination for optimizing catalytic performance is an unpredictable challenge. Herein, we report that catalyst and photosensitizer monomers are selectively grafted one-by-one addition onto the electrode surface by interfacial electrosynthesis to achieve composition and sequence-controlled oligomer photoelectrocatalytic monolayers. This electrosynthesis relies on the oxidative coupling reaction of carbazole and the reductive coupling reaction of vinyl on the catalyst and photosensitizer monomers, and it initiates on self-assembled monolayers and propagates with alternating positive and negative potentials. Each addition and completion of the target monomer can be quantitatively identified and monitored by optical and electrical responses and their linear coefficients as a function of reaction steps. The resulting composition and sequence-controlled monolayers exhibit tuning electrocatalytic behaviors including water splitting and CO₂ reduction, indicating an efficient way to optimize the electro- and photocatalytic functions and performance of molecular materials.