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

Nguyen-Phan, T. D., National Energy Technology Laboratory
Kauffman, D. R., National Energy Technology Laboratory
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.