Fine Tuning of Charge Motion Over Homogeneous Transient Metal Chalcogenides Heterostructured Photoanodes for Photoelectrochemical Water Splitting

Abstract Metal oxides (MOs)-based photoelectrochemical (PEC) cell, as an environmentally friendly and sustainable technique to convert solar energy to chemical energy, has been attracting enduring interest in the past few decades. However, sluggish charge transport dynamics, tough vectorial controllable charge migration route, and confined light absorption of MOs retard the solar energy conversion efficiencies of MOs-based photoelectrodes. Apart from MOs, transition metal chalcogenides (TMCs) photoanodes directly growing on the conductive substrate for PEC water splitting have been so far rarely reported albeit their generic merits of large absorption coefficient, suitable energy level alignment, and abundant active sites. Herein, we conceptually demonstrate the tunable construction of homogeneous TMCs heterostructured photoanodes (In2S3-CdIn2S4, In2S3-ZnIn2S4) by a facile, easily accessible, simple yet efficient cation exchange strategy at ambient conditions. The thus-designed TMCs composite photoanodes demonstrate significantly enhanced PEC water splitting performances relative to the pristine counterparts under both visible and simulated solar light irradiation, which is predominantly attributed to the markedly improved interfacial charge transfer/separation afforded by the favorable energy level configuration between the TMCs substrate and newly formed TMCs phase. We additionally ascertain that such ion exchange approach is universal for crafting other TMCs-based hybrid photoanodes. Our work is expected to provide an emerging avenue to craft a large variety of TMCs-based heterostructured photoanodes for solar energy conversion.