Coupling NiCo catalysts with carbon quantum dots on hematite photoanodes for highly efficient oxygen evolution

Abstract

Highly efficient hole transfer from photoanodes to oxygen evolution catalysts is crucial for solar photoelectrochemical (PEC) water splitting. Herein, we demonstrated the coupling of the NiCo catalyst with carbon quantum dots (CDs) on the surfaces of α-Fe₂O₃ photoanodes, resulting in one of the highest currently known PEC activities of 4.26 mA cm⁻² (1.23 V versus the reversible hydrogen electrode, AM 1.5G). Furthermore, the H₂ generation rate from PEC water splitting could reach up to 74.9 μmol cm⁻² h⁻¹ with a faradaic efficiency of nearly 99%. The detailed experimental results clearly reveal that these CDs acted as an efficient medium for remarkably promoting hole transport from anodes to catalysts and selectively tailoring the electronic structure of surface-active sites, which significantly promoted the surface charge separation and oxygen evolution process. This work offers unique insights into the design and construction of highly efficient photoanodes for PEC water splitting applications.