Efficient photoelectrochemical water splitting of metal-porphyrin decorated on BiVO4 photoanode

Decorating sensitizers with excellent light harvesting ability such as porphyrins onto semiconducting materials should be a promising photocatalyst design protocol for prompting electron injection and charge separation at photoelectrolytic interfaces. Here we rationally construct three composite catalysts consisting of BiVO4 and metalloporphyrins (MTPP, M = Co, Ni and Cu) with different metal ion species, nominated as BiVO4/MTPP. The construction of BiVO4/MTPP composites with enhanced light absorption is confirmed by a series of spectroscopic techniques. Under AM 1.5G light irradiation, the composites' potential as photocatalysts for water splitting is investigated. It is found that the photoelectrochemical performance is dependent on the type of central metal ion in the porphyrin core. Among the three BiVO4/MTPP composites, the superior BiVO4/MTPP exhibits the highest photocurrent density of 3.9 mA cm-2 at 1.23 V vs. RHE, which is thought to be due to enhanced electron-hole pair production and a slower recombination rate. Our finding demonstrates a successful porphyrin-doped photocatalyst and highlights the importance of metal type in metalloporphyrins for photoelectrochemical water splitting applications.