Ultrathin carbon interim layer encapsulation for constructing p − n heterojunction photoanode towards photoelectrochemical water splitting

Abstract

Interfacial charge transfer and separation are both critical to the solar energy conversion efficiency, whereas it remains an enduring challenge. This work demonstrates the synergetic enhancement of interfacial charge transfer efficiency and bulk charge separation by depositing p-type Co3O4 cocatalyst onto n-type TiO2 nanotube arrays (TNTAs) that are uniformly coated with an ultrathin carbon layer, forming a p − n Co3O4/TNTAs heterojunction. Being highly dispersed on the surface of photoanodes, Co3O4 quantum dots retard forming charge recombination centers at the photoanode/cocatalyst interface, which facilitates hole transport. Simultaneously, ultrathin intermediate carbon layer boosts interfacial electron transfer kinetics, resulting in effective spatial charge separation and considerably improved photoelectrochemical (PEC) water splitting performances.