Interfacial engineering of lattice coherency at ZnO-ZnS photocatalytic heterojunctions

Abstract

Heterogeneous semiconductor interfaces with built-in electric fields are central to promoting directional carrier migration and separation for charge-induced redox reactions. Unfortunately, most heterointerfaces are structurally incoherent due to large lattice mismatch accompanied with multiple dangling bonds, imposing high energy barriers for charge transport. Here, we report the atomic engineering of ZnO-ZnS heterogeneous interfaces, transforming from incoherent characters to semi-coherent counterparts through annealing-induced spontaneous assembly of ZnS nanoparticles on single-crystalline ZnO nanowires, which is substantiated by aberration-corrected scanning transmission electron microscopy. Theoretical calculations reveal that semi-coherent interfaces are beneficial in annihilating deep local gap states and thus, remarkably reducing carrier transport barrier height by 1.25 eV. This contributes to a 5.8-fold enhanced photocatalytic hydrogen production rate with an improved stability. The study provides physical insights into interfacial lattice engineering of photocatalytic heterojunctions and offers a convenient strategy to convert incoherent interfaces to photocatalytically favorable semi-coherent phase boundaries for solar energy utilization. • The coherency of ZnO-ZnS interfaces was atomically engineered by thermal annealing • Creation of semi-coherent interfaces by grain rotation facilitates carrier transfer • Semi-coherent interfaces endow the composites with enhanced photocatalytic property Interfacial interaction in heterogeneous systems has a profound effect on photocatalytic performance. However, the intrinsic phase boundaries between two dissimilar photocatalytic materials are more prone to establish randomly incoherent interfaces containing multiple dangling bonds, due to the large discrepancy in their lattice parameters. This work opens up a convenient scenario to convert incoherent interfaces into plane-matched semi-coherent counterparts through annealing-induced grain rotation. These lattice-matching semi-coherent interfaces are conducive to annihilating deep gap states, resulting in a substantially reduced barrier height for carrier transport, which contributes to strengthened photocatalytic property and improved photostability. Overall, our report provides a practical paradigm for the atomic engineering of interface coherency of advanced photocatalysts, opening a promising avenue for the construction of heterojunctions. The incoherent ZnO-ZnS photocatalytic heterojunctions could be atomically engineered into semi-coherent phase boundaries by the spontaneous assembly of ZnS nanoparticles on ZnO nanowires via a convenient annealing strategy. The lattice-matching interface coherency reduces carrier transport barrier height by removing interfacial dangling bonds, giving rise to optimized interfacial electronic structure for promoted charge separation and strengthened photocatalytic activity.