Authors
Sakthivel Perumal, Taewaen Lim, Kyung Hee Oh, Shin Wook Kang, Jee Hyeon Kim, Hyunseob Lim, Dong Young Chung, Kang Hyun Park, Ji Chan Park, Junhyeok Seo
Published in
Small (Weinheim an der Bergstrasse, Germany). Pages e75015. Aug 19, 2026. Epub Aug 19, 2026.
Abstract
Electrochemical CO2 reduction to formate on copper oxide catalysts is often limited by poor selectivity due to competing multi-electron pathways and by rapid reduction of active sites accompanied by severe structural reconstruction under cathodic bias. Here, we report a well-defined Cu2O|graphene heterostructure that enables highly selective CO2-to-formate conversion while maintaining a Cu+-state active phase during electrocatalysis. The electrochemical reactivity of distinct Cu oxidation states (Cu0, Cu+, and Cu2+) supported on graphene was systematically compared, revealing pronounced oxidation-state-dependent CO2 reduction behavior. Strong electronic coupling at the Cu2O|graphene interface regulated interfacial electron transfer, suppressing over-reduction to metallic Cu and preserving the catalytic structure during electrolysis. Time-resolved ex situ X-ray diffraction, Cu LMM Auger spectroscopy, Cu K-edge XANES, in situ Raman spectroscopy and high-resolution transmission electron microscopy collectively suggested the retention of Cu+-rich environment on graphene during CO2RR, in contrast to Cu|graphene and CuO|graphene. Consequently, stabilized Cu+ sites at the Cu2O|graphene interface favored a proton-coupled electron transfer pathway via the *OCHO intermediate, delivering a high formate Faradaic efficiency of 78% at -0.86 V vs. RHE. This work establishes interfacial electronic coupling as an effective strategy to stabilize metastable Cu+ active sites for selective CO2-to-formate conversion.
PMID:
42619357
Bibliographic data and abstract were imported from PubMed on 20 Aug 2026.
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