(127g) Highly Active, Robust 3D Interconnected Porous Oxide-Derived Copper Electrocatalysts for Selective Conversion of CO2 into Fuels

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. Expensive noble metal catalysts have been extensively studied for electrochemically converting CO₂ into CO with high selectivity at low overpotentials. However, there is also a need to abate and/or replace the use of precious metals with Earth-abundant transition metals. In this work, we report hierarchical CuO-derived inverse opal catalysts which demonstrated impressive CO selectivity compared with commercially-available CuO powders and other reported copper-based catalysts. Such a 3D interconnected porous catalyst composed of small nanoparticles surprisingly produced CO with a peak Faradaic efficiency (FE) of 72.5% at -0.6 V vs. RHE and was highly robust during 24-hour CO₂ electrolysis. Selective C₁ production alongside negligible H₂ evolution could be ascribed to a local pH increment inside the interconnected porous structure and rapid consumption of CO₂ and protons at the highly roughened catalyst surface during the electrolysis. In addition, the in situ synchrotron X-ray absorption fine structure and X-ray diffraction measurements allowed us to probe the reduction of CuO into metallic Cu with dominant active Cu (111) surfaces under electrocatalytic conditions. The CO₂-to-CO outperformance of our 3D porous oxide-derived copper materials over typical oxidized copper catalysts could be ascribed to the synergistic effect of roughened, interconnected inverse opal morphology and surface structure which would highly correlate with weak binding of the intermediate species, lower adsorbate mobility, and reduced reactant availability per active site. Our anticipated findings may open an opportunity for rational design of promising, high-performance, less expensive electrocatalysts to produce sustainable fuels and value-added chemicals from fossil fuel-generated CO₂ emission.