In situ imaging electrocatalytic CO reduction and evolution reactions in all-solid-state Li-CO nanobatteries.

Li-CO batteries are promising energy storage devices owing to their high energy density and possible applications for CO capture. However, still some critical issues, such as high charging overpotential and poor cycling stability caused by the sluggish decomposition of LiCO discharge products, need to be addressed before the practical applications of Li-CO batteries. Exploring highly efficient catalysts and understanding their catalytic mechanisms for the CO reduction reaction (CORR) and evolution reaction (COER) are critical for the application of Li-CO batteries. However, the direct imaging of electrocatalysis during CORR and COER is still elusive. Herein, we report the in situ imaging of electrocatalysis during CORR and COER in a Li-CO nanobattery using a Ni-Ru-coated α-MnO nanowire (Ni-Ru/MnO) cathode in an advanced aberration corrected environmental transmission electron microscope. During the CORR, a thick LiCO and carbon mixture layer was formed on the surface of the Ni-Ru/MnO nanowires via 4Li + 3CO + 4e→ 2LiCO + C. During the COER, the as-formed LiCO decomposed via 2LiCO→ 2CO + O + 4Li + 4e, while the as-formed amorphous carbon remained. In contrast, the decomposition of LiCO on bare MnO nanowires was difficult, underscoring the important Ni-Ru bimetal electrocatalytic role in facilitating the COER. Our results provide an important understanding of the CO chemistry in Li-CO batteries, possibly helping in the designing of Li-CO batteries for energy storage applications.