The production of value-added chemicals and fuels from CO2 and water by highly efficient, selective, robust electrocatalytic materials is of vital interest to address the energy challenges. In this work, we report a hierarchical CuO-derived inverse opal (CuO-HIO) electrocatalyst which demonstrated impressive CO selectivity and negligible H2 evolution at high current densities (achieved ~35 mA cm-2 at -1.2 V vs. RHE). Such a three-dimensional interconnected porous network with voids about 200 nm surprisingly exhibited a Faradaic efficiency (FE) of 72.5% for CO production at -0.6 V vs. RHE and was very stable during 24-hour CO2 electrolysis (~ 3 mA cm-2). Significant changes in in situ Cu K-edge XANES and Fourier transformed EXAFS spectra dynamically revealed the transformation of Cu2+ to Cu0 species within 60 min at -0.6 V vs. RHE. Such an observation was well consistent with the gradual emergence of three primary diffractions of metallic copper in the in situ time-resolved XRD patterns under the working condition. An increase in Cu fraction and particle size as a function of electrolysis time was clearly obtained. CO2-to-CO outperformance of CuO-HIO catalyst over typical oxidized copper catalysts could be ascribed to (i) the mass transport limitation and local pH effect induced by unique hierarchical morphology, (ii) highly roughened surface, and (iii) in situ reduction of Cu2+ to stabilized metallic Cu active sites during the electrolysis. Our findings may open an opportunity for rational design of promising, high-performance electrocatalysts for renewable fuel productions from fossil fuel-generated CO2 emission.

Probing the in situ electrochemical reduction of hierarchical oxide-derived inverse opals during the conversion of carbon dioxide into fuels

2019 Spring National Meeting

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