SPR-Effect Enhanced Semimetallic Bi⁰/p-BiOI/n-CdS Photocatalyst with Spatially Isolated Active Sites and Improved Carrier Transfer Kinetics for H₂ Evolution

Abstract

Bi0/p-BiOI/n-CdS was first designed to be applied to hydrogen evolution by water splitting. UV–vis diffuse reflectance spectroscopy (DRS) tests show that Bi0 has an surface plasmon resonance (SPR) absorption peak at 428 nm. Theoretical calculations show that electrons generated in Bi were injected into BiOI. Due to the SPR effect of Bi0, both electron transfer kinetics and optical absorptivity were improved. Bi0 also worked as a medium for storing and transferring electrons. Tauc plots and M–S tests show that Bi0 has a band structure similar to semiconductors, indicating that Bi0 exhibits semiconductivity. Therefore, two continuous heterojunctions Bi0/p-BiOI and p-BiOI/n-CdS were formed. Finally, the H2 and O2 evolution active sites were spatially separated, thus alleviating the recombination of carriers and photocorrosion of CdS. Collectively, Bi0/BiOI and CdS were combined to construct an SPR-enhanced double heterojunction structure. As a result, a hydrogen production efficiency of 31 mmol h–1 was achieved.