Enriched oxygen vacancies of Cu2O/SnS2/SnO2 heterostructure for enhanced photocatalytic reduction of CO2 by water and nitrogen fixation

Niwesh Ojha; Abhinav Bajpai; Sushant Kumar

doi:10.1016/j.jcis.2020.10.056

Enriched oxygen vacancies of Cu₂O/SnS₂/SnO₂ heterostructure for enhanced photocatalytic reduction of CO₂ by water and nitrogen fixation

J Colloid Interface Sci. 2021 Mar:585:764-777. doi: 10.1016/j.jcis.2020.10.056. Epub 2020 Oct 20.

Authors

Niwesh Ojha¹, Abhinav Bajpai¹, Sushant Kumar²

Affiliations

¹ Gas-Solid Interaction Laboratory, Department of Chemical and Biochemical Engineering, Indian Institute of Technology Patna, Bihta, Patna 801 106, Bihar, India.
² Gas-Solid Interaction Laboratory, Department of Chemical and Biochemical Engineering, Indian Institute of Technology Patna, Bihta, Patna 801 106, Bihar, India. Electronic address: sushantkumar@iitp.ac.in.

PMID: 33127052
DOI: 10.1016/j.jcis.2020.10.056

Abstract

When two semiconductors are electronically coupled, their photocatalytic performance can be greatly enhanced. Herein, we formed a heterostructure between Cu₂O and SnS₂/SnO₂ nanocomposite using a solvothermal reactor, which reduced CO₂ by H₂O at ambient conditions to produce CO, H_2, and CH₄. With inclusion of Cu₂O, apparent quantum yield, a measure of photoactivity, has increased from 7.16% to 8.62%. Also, the selectivity of CH₄ over CO was approximately 1.8-times higher than that of SnS₂/SnO₂. Interestingly, the as-synthesized catalysts were able to fix N₂ to NH₃ under light illumination at ambient conditions. Dissecting the mechanism into basic steps, it is shown that oxygen vacancies within the catalysts act as trapping sites for photo-induced charge carriers which strongly influenced the reactivity and selectivity of product. Additionally, oxygen vacancies act as active sites to chemisorb nitrogen molecules, which follow associative steps to generate NH₃. In absence of sacrificial agent, the NH₄⁺ generation rate was66.35μmol.g^-1h^-1 for Cu₂O/SnS₂/SnO₂, which is 1.9-fold higher than SnS₂/SnO₂. Formation of a p-n heterojunction between Cu₂O and SnS₂/SnO₂ nanocomposite offered favorable photoreductive potentials and high stability, mainly owing to their intimate interfacial contact. The results clearly illustrate a promising strategy to use oxygen vacancies rich heterostructure for wide application in photocatalysis.

Keywords: Nanocomposite; P-n heterojunction; Photocatalyst; Selectivity; Vacancies.