A mesh-like BiOBr/Bi2S3 nanoarray heterojunction with hierarchical pores and oxygen vacancies for broadband CO2 photoreduction

Abstract

Exploring highly efficient heterostructured photocatalysts for converting CO₂ to value-added chemicals has long been pursued, which is mainly limited by inefficient visible/near-infrared (NIR) photon capture, undesirable electron–hole recombination, and insufficient accessible active sites. Herein, we report a robust heterojunction photocatalyst, consisting of mesh-like Bi₂S₃ nanoarrays epitaxially grown on BiOBr nanoplates via a facet-selective topotactic transformation process, for synchronically overcoming the aforementioned obstacles and markedly advancing the CO₂ conversion efficiency: (i) vertically aligned Bi₂S₃ nanowalls harness solar photons from the visible to NIR region beyond 1000 nm and minimize the light shielding effect on BiOBr substrates, while multiple light reflection in the mesh pores enclosed by Bi₂S₃ walls and BiOBr supports accounts for improved light utilization efficiency; (ii) intimate coupling of BiOBr and Bi₂S₃ endows the heterojunction with enhanced charge separation efficiency through the interfacial Bi–S/Br–Bi bonds between them; (iii) etched pores and oxygen vacancies on the surface of BiOBr strengthen the adsorption and activation of CO₂, and decrease the barrier of the rate-determining step in CO₂-to-CO reduction. By virtue of these distinguished features, the optimized BiOBr/Bi₂S₃ heterojunction delivers an outstanding CO evolution rate of 103.5 μmol g_cat⁻¹ h⁻¹ and selectivity of 90.1% under broadband light irradiation. This work sets up a significant milestone in simultaneously manipulating the three critical steps in photocatalysis during the construction of novel hybrid architectures for solar energy conversion applications.