3D Porous Pyramid Heterostructure Array Realizing Efficient Photo‐Electrochemical Performance

Abstract Direct photo‐electrochemical (PEC) water splitting is of great practical interest for developing a sustainable energy systems, but remains a big challenge owing to sluggish charge separation, low efficiency, and poor stability. Herein, a 3D porous In 2 O 3 /In 2 S 3 pyramid heterostructure array on a fluorine‐doped tin oxide substrate is fabricated by an ion exchange–induced synthesis strategy. Based on the synergistic structural and electronic modulations from density functional theory calculations and experimental observations, 3D porous In 2 O 3 /In 2 S 3 photoanode by the protective layer delivers a low onset potential of ≈0.02 V versus reversible hydrogen electrode (RHE), the highest photocurrent density of 8.2 mA cm −2 at 1.23 V versus RHE among all the In 2 S 3 photoanodes reported to date, an incident photon‐to‐current efficiency of 76% at 400 nm, and high stability over 20 h for PEC water splitting are reported. This work provides an alternative promising prototype for the design and construction of novel heterostructures in robust PEC water splitting applications.