Synthesis of Cu2O Nanostructures with Tunable Crystal Facets for Electrochemical CO2 Reduction to Alcohols

Bingqian Liu; Xi Yao; Zijing Zhang; Changhai Li; Jiaqing Zhang; Puyao Wang; Jiayi Zhao; Yafei Guo; Jian Sun; Chuanwen Zhao

doi:10.1021/acsami.1c03850

Synthesis of Cu₂O Nanostructures with Tunable Crystal Facets for Electrochemical CO₂ Reduction to Alcohols

ACS Appl Mater Interfaces. 2021 Aug 25;13(33):39165-39177. doi: 10.1021/acsami.1c03850. Epub 2021 Aug 12.

Authors

Affiliations

¹ School of Energy and Mechanical Engineering, Nanjing Normal University, Nanjing 210042, China.
² State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, China.
³ State Grid Anhui Electric Power Research Institute, Hefei 230022, China.

PMID: 34382393
DOI: 10.1021/acsami.1c03850

Abstract

Electrochemical CO₂ reduction enables the conversion of intermittent renewable energy to value-added chemicals and fuel, presenting a promising strategy to relieve CO₂ emission and achieve clean energy storage. In this work, we developed nanosized Cu₂O catalysts using the hydrothermal method for electrochemical CO₂ reduction to alcohols. Cu₂O nanoparticles (NPs) of various morphologies that were enclosed with different crystal facets, named as Cu₂O-c (cubic structure with (100) facets), Cu₂O-o (octahedron structure with (111) facets), Cu₂O-t (truncated octahedron structure with both (100) and (111) facets), and Cu₂O-u (urchin-like structure with (100), (220), and (222) facets), were prepared by regulating the content of a polyvinyl pyrrolidone (PVP) template. The electrochemical CO₂ reduction performance of the different Cu₂O NPs was evaluated in the CO₂-saturated 0.5 M KHCO₃ electrolyte. The as-synthesized Cu₂O nanostructures were capable of reducing CO₂ to produce alcohols including methanol, ethanol, and isopropanol. The alcohol selectivity of the different Cu₂O NPs followed the order of Cu₂O-t < Cu₂O-u < Cu₂O-c < Cu₂O-o (with the total Faradaic efficiencies of alcohol products of 10.7, 25.0, 26.2, and 35.4%). The facet-dependent effects were associated with the varied concentrations of oxygen-vacancy defects, different energy barriers of CO₂ reduction, and distinct Cu-O bond lengths over the different crystal facets. The desired Cu₂O-o catalyst exhibited good reduction activity with the highest partial current density of 0.51 mA/cm² for alcohols. The Faradaic efficiencies of alcohol products were 4.9% for methanol, 17.9% for ethanol, and 12.6% for isopropanol. The good electrochemical CO₂ reduction performance was also associated with the surface reconstruction of Cu₂O, which endowed the catalyst with abundant Cu⁰ and Cu⁺ sites for promoted CO₂ activation and stabilized CO* adsorption for enhanced C-C coupling. This work will provide a new route for enhancing the alcohol selectivity of nanostructured Cu₂O catalysts by crystal facet engineering.

Keywords: alcohols selectivity; crystal facet-dependent effect; electrochemical CO2 reduction; nanostructured Cu2O catalysts; structure−property−activity relationships.