Enriched oxygen vacancies of Cu 2 O/SnS 2 /SnO 2 heterostructure for enhanced photocatalytic reduction of CO 2 by water and nitrogen fixation.

When two semiconductors are electronically coupled, their photocatalytic performance can be greatly enhanced. Herein, we formed a heterostructure between Cu ₂ O and SnS ₂ /SnO ₂ nanocomposite using a solvothermal reactor, which reduced CO ₂ by H ₂ O at ambient conditions to produce CO, H _2, and CH ₄ . With inclusion of Cu ₂ O, apparent quantum yield, a measure of photoactivity, has increased from 7.16% to 8.62%. Also, the selectivity of CH ₄ over CO was approximately 1.8-times higher than that of SnS ₂ /SnO ₂ . Interestingly, the as-synthesized catalysts were able to fix N ₂ to NH ₃ 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 NH ₃ . In absence of sacrificial agent, the NH ₄ ⁺ generation rate was66.35μmol.g ^-1 h ^-1 for Cu ₂ O/SnS ₂ /SnO ₂ , which is 1.9-fold higher than SnS ₂ /SnO ₂ . Formation of a p-n heterojunction between Cu ₂ O and SnS ₂ /SnO ₂ 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.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier Inc. All rights reserved.)