CuO (111) Microcrystalline Evoked Indium–Organic Framework for Efficient Electroreduction of CO2 to Formate

Electrochemical reduction of carbon dioxide (CO₂RR) to formate is economically beneficial but suffers from poor selectivity and high overpotential. Herein, enriched microcrystalline copper oxide is introduced on the surface of indium-based metal-organic frameworks. Benefiting from the CuO (111) microcrystalline shell and formed catalytic active In-Cu interfaces, the obtained MIL-68(In)/CuO heterostructure display excellent CO₂RR to formate with a Faradaic efficiency (FE) as high as 89.7% at low potential of only -0.7 V vs. RHE in a flow cell. Significantly, the membrane electrode assembly (MEA) cell based on MIL-68(In)/CuO exhibit a remarkable current density of 640.3 mA cm^-2 at 3.1 V and can be stably operated for 180 h at 2.7 V with a current density of 200 mA cm^-2. The ex/in situ electrochemical investigations reveal that the introduction of CuO increases the formation rate of the carbon dioxide reduction intermediate ^*HCOO^- and inhibits the competitive hydrogen evolution reaction. This work not only provides an in-depth study of the mechanism of the CO₂RR pathways on In/Cu composite catalyst but also offers an effective strategy for the interface design of electrocatalytic carbon dioxide reduction reaction.