Photoelectrochemical Dicarboxylation of Styrene with CO2 to Phenylsuccinic Acid on Ni-Decorated Silicon Photocathode

Abstract

The conversion of CO2 into value-added chemicals is highly critical for sustainable development. Among the various strategies, the dicarboxylation of alkenes with CO2 offers a highly attractive route to access synthetically valuable dicarboxylic acids, which serve as key intermediates in the production of polymers and pharmaceuticals. Photoelectrochemical (PEC) catalysis carboxylation represents an efficient and sustainable carboxylation strategy, offering distinct advantages including mild reaction conditions, cost-effectiveness, and environmental compatibility. In this study, an efficient PEC system is presented for the carboxylation of styrene using a Ni-modified p-type micro-pyramid silicon (Ni/p-Si) photocathode. The incorporation of Ni catalyst significantly suppresses charge recombination and accelerates charge transfer at the electrode-electrolyte interface, thereby enhancing the overall photoelectrochemical performance. The optimized Ni/p-Si photocathode achieved 77.7% Faradaic efficiency (FE) for phenylsuccinic acid at −2.4 V vs. Ag/AgCl, with a photocurrent density of −4.5 mA cm−2. Moreover, this PEC platform demonstrates moderate FEs across a range of substituted styrenes, indicating good functional group tolerance. Mechanistic studies reveal that the reaction proceeds via single-electron reduction of styrene to generate radical anions, which undergo CO2 addition followed by further reduction and subsequent attack on a second CO2 molecule to yield succinic acid. These findings broaden the scope of CO2 utilization through selective and sustainable C-C bond formation processes.