The performance of supported metal catalysts can depend on many factors, including metal particle size and dispersion and metal− support interactions, and differentiation of these effects is challenging because of their interwoven relationship. Copper/ceria catalysts are wellknown redox catalysts studied in the conversion of CO and CO 2 via oxidation and/or reduction pathways. The redox behaviors of each species, Cu-CuO and CeO x -CeO 2 , are often suggested to be interlinked, allowing ceria-supported copper domains to outperform copper species on other, nonredox active supports. In this work, the catalytic activity of nanosized Cu supported on either cerium oxide or mesoporous silica is explored using samples where the Cu weight loading, particle size, and dispersion of Cu are held constant to highlight the impact of the two supports on catalytic performance without additional influencing factors. The Cu/CeO 2 catalysts are synthesized via a spaceconfined method to limit the growth of CeO 2 particles and to achieve a high dispersion of Cu. Through in situ XRD and XAS, it is shown that the presence of Cu nanoparticles on the CeO 2 support lowers the reduction temperature of CeO 2 , allowing formation of oxygen vacancies at low temperatures <300 °C. The Cu/CeO x catalyst demonstrates 100% CO selectivity in the low temperature (300 °C) and ambient pressure conversion of CO 2 to CO, even when approaching equilibrium conversion. Moreover, this catalyst is approximately 4 times more active than the corresponding Cu/SiO 2 catalyst with otherwise similar structural attributes. The potential reaction pathways are probed by in situ FTIR and in situ XAS at various temperatures, identifying Cu + -CO species and oxygen vacancies forming under some conditions. The collected experimental evidence also suggests a reaction sequence for CO 2 hydrogenation over Cu/CeO x catalysts, consistent with DFT reports in the literature.

Treasure OVE: The performance of doped ceria for CO2 adsorption is investigated by oxygen vacancy engineering (OVE), that is, the formation and regeneration of oxygen vacancies. The doping and synthesis methods can be adapted to OVE, while reduction with hydrogen effectively restores the number of oxygen vacancies back to its original level. The regeneration characteristics of ceria and the catalytic conversion of adsorbed CO2 at moderate temperatures are also explored.

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It is essential to decouple the interfacial reactions taking place at the anode and cathode in rechargeable batteries. However, due to the reactive nature of Li, it is challenging to use Li‐metal batteries (LMBs) protocol to decouple the interfacial reactions. The by‐products from the anode or cathode become mixed in Li/NMC111 cells, which make decoupling interfacial reactions difficult. Here, reactions at electrodes are successfully decoupled and demystified using a protocol combining anode‐free LMB (AFLMB) with online electrochemical mass spectroscopy. LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) and EC/ethyl methyl carbonate (1:1 v/v%) electrolytes are used to compare interfacial reactions in Li/NMC111 and Cu/NMC111 cells. In Cu/NMC111, the evolution of CO2, CO, and C2H4 gases at the initial stage of first charging is due to interfacial reactions at Cu surface due to solid–electrolyte‐interphase formation. However, the evolution of CO2 and CO gases at high voltage in the entire cycles is associated with chemical and/or electrochemical electrolyte oxidation at the cathode. This work paves a new concept to decouple interfacial reactions at electrodes for developing electrochemically stable electrolytes to improve the performance with the long‐cycling life of AFLMBs and LMBs.