Electrochemical conversion of CO₂ into HCOO⁻ in a synergistic manner by a nanocomposite of Zn₂SnO₄/ZnO

Exploring environmentally friendly nanomaterials as alternatives to toxic metals for electrocatalytic CO₂ reduction into formate is very important. Designing a nanocomposite catalyst with different phase components is an underlying strategy to achieve prominent catalysts for electrochemical CO₂ reduction owing to the potential capacity to regulate electronic structure by interfacial interactions. Herein, we report a novel nanocomposite with components of cublic-like Zn₂SnO₄ and nanosheet-structured ZnO (Zn₂SnO₄/ZnO) as an efficient electrocatalyst for the CO₂ reduction reaction (CO₂RR). This strategy can reduce the use of toxic metals and the cost of the catalyst. The composite exhibited a maximum faradaic efficiency (FE) of 98% for the C₁ product, and even approached 90% for formate production at −1.0 V versus the reversible hydrogen electrode, along with excellent durability. In constrast, the maximum FE_HCOOH of a single ZnO component or Zn₂SnO₄ component were both <50% over the potential window. Coupling of X-ray photoelectron/adsorption spectroscopy and electrochemical measurements revealed interfacial charge transfer and oxygen vacancies to result in an optimized electronic structure of Zn₂SnO₄/ZnO. This was favorable for an HCOO* intermediate-involved reaction pathway, together with an enlarged electochemcial active area, which boosted the selectivity and activity of formate synergistically. © 2023 The Royal Society of Chemistry.