Efficient photocatalytic hydrogen production on defective and strained black bismuth (III) oxide.

Bismuth (III) oxide (Bi 2 O 3) has been highly studied as a photocatalyst for green hydrogen production due to its low band gap, yet its efficiency requires enhancement. This study synthesizes a defective and strained black Bi 2 O 3 by severe straining under high pressure, via a high-pressure torsion method, to improve its photocatalytic hydrogen production. The material rich in oxygen vacancies exhibits a ten-fold improvement in water splitting with excellent cycling stability. Such improvement is due to improved light absorption, narrowing band gap and reduced irradiative electron-hole recombination. Moreover, the valence band bottom energy positively increases by straining leading to a high overpotential for hydrogen production. This research highlights the potential of vacancies and lattice strain in developing dopant-free active catalysts for water splitting. • Defective and strained Bi 2 O 3 was produced by severe straining under high pressure. • The material, rich in oxygen vacancies, exhibits high light absorption and a narrow band gap. • It shows ten-fold improvement in photocatalytic hydrogen production with excellent cycling. • Strain and vacancies reduce recombination and enhance overpotential for H 2 evolution. [ABSTRACT FROM AUTHOR]