Cobalt porphyrin/molybdenum disulfide nanoensembles for light-assisted electrocatalytic water oxidation and selective hydrogen peroxide production

Abstract

Abstract The development of photo/electroactive catalysts sustainably producing hydrogen from water splitting and selectively hydrogen peroxide is of paramount importance to alleviate climate change effects. Herein, an anionic cobalt porphyrin (CoP) derivative is electrostatically interfaced with a positively charged modified molybdenum disulfide (MoS2), forming CoP/MoS2, which is accordingly employed as nonprecious photo/electrocatalyst for water oxidation reaction (WOR) and selective H2O2 production. According to the results, CoP/MoS2 shows remarkable bifunctional photo/electrocatalytic performance for WOR and 2e− pathway O2 reduction reaction (ORR) in alkaline electrolyte. Upon visible light irradiation, electrochemical measurements on a fluorine-doped tin oxide (FTO) coated glass electrode reveal an onset potential of 0.595 mV (ORR) and 1.575 mV (WOR) vs. reversible hydrogen electrode, being improved by approximately 80 mV, in both cases, compared to the dark conditions. Notably, the use of the FTO set-up not only enabled us to evaluate the photo/electrocatalytic activity of the CoP/MoS2 nanoensemble but also mimics the practical conditions in photo/electrochemical devices. The outstanding bifunctional photo/electrocatalytic performance of CoP/MoS2 is attributed to (a) the use of CoP as versatile single-atom molecular catalyst and photosensitizer (b) the strong ion-pair interactions between cationic modified MoS2 and the anionic CoP derivative, which prevent aggregation, ensuring better accessibility of the reactants to cobalt active sites, and (c) the co-existence of 1T and 2H phase at modified MoS2, offering improved electrical conductivity and intrinsic electrocatalytic activity along with enhanced intraensemble electronic interactions upon illumination. This work is expected to inspire the design of advanced and low-cost materials for the sustainable production of renewable fuels.