Designing Type-II p-SiCC4/XO (X = Sn, Pb) van der Waals Heterojunctions with a Built-in Electric Field as Promising Photocatalysts for Highly Efficient Overall Water Splitting

Abstract

To overcome the intrinsic exciton utilization bottlenecks in two-dimensional photocatalysis, we designed the novel p-SiCC4/XO (X = Sn, Pb) van der Waals heterojunctions and systematically investigated the exciton-related properties and photocatalytic performance using first-principles calculation. The results demonstrate that the p-SiCC4/XO (X = Sn, Pb) heterojunctions possess 2.00 and 2.18 eV indirect band gap and type-II band alignment, and the band edge alignments fully span the redox potentials of water splitting. These heterostructures also exhibit distinctive auxetic characteristics with the maximum values of -0.05 and -0.025, respectively. The interfacial built-in electric field drives spatial charge separation and sustains long radiation lifetime interlayer excitons (1.1-2.6 ns), enabling efficient exciton dissociation with suppressed recombination. More importantly, the p-SiCC4/XO (X = Sn, Pb) heterojunctions only can spontaneously proceed the oxygen evolution half-reaction at pH = 7, however, the overall water splitting redox reaction on p-SiCC4/PbO heterojunction can be nearly spontaneously driven under the light illumination at pH = 0. In addition, the p-SiCC4/XO (X = Sn, Pb) heterojunctions yield exceptional solar-to-hydrogen efficiencies of 16.87% (p-SiCC4/SnO) and 12.67% (p-SiCC4/PbO). These findings indicate that there heterojunctions show great application prospect as water splitting photocatalyst.