Guiding the Catalytic Properties of Copper for Electrochemical CO2 Reduction by Metal Atom Decoration.

Tuning bimetallic effects is a promising strategy to guide catalytic properties. However, the nature of these effects can be difficult to assess and compare due to the convolution with other factors such as the catalyst surface structure and morphology and differences in testing environments. Here, we investigate the impact of atomic-scale bimetallic effects on the electrochemical CO2 reduction performance of Cu-based catalysts by leveraging a systematic approach that unifies protocols for materials synthesis and testing and enables accurate comparisons of intrinsic catalytic activity and selectivity. We used the same physical vapor deposition method to epitaxially grow Cu(100) films decorated with a small amount of noble or base metal atoms and a combination of experimental characterization and first-principles calculations to evaluate their physicochemical and catalytic properties. The results indicate that the metal atoms segregate to under-coordinated Cu sites during physical vapor deposition, suppressing CO reduction to oxygenates and hydrocarbons and promoting competing pathways to CO, formate, and hydrogen. Leveraging these insights, we rationalize bimetallic design principles to improve catalytic selectivity for CO2 reduction to CO, formate, oxygenates, or hydrocarbons. Our study provides one of the most extensive studies on Cu bimetallics for CO2 reduction, establishing a systematic approach that is broadly applicable to research in catalyst discovery.

Operando X-ray absorption spectroscopy of hyperfine ß-FeOOH nanorods modified with amorphous Ni(OH)2 under electrocatalytic water oxidation conditions.

Operando X-ray absorption spectroscopy was employed to study an active electrocatalyst, hyperfine ß-FeOOH nanorods (∅ 3 × 15 nm) surface-modified with amorphous Ni hydroxide. The nearest neighbor structure and valence of Fe3+ ions did not change under water oxidation conditions, while changes in the nearest neighbor ordering of Ni2+ ions and a reversible transition to Ni3+ were observed in accordance with the electrical bias for the reaction.

In situ X-ray Raman spectroscopy and magnetic susceptibility study on the Li[Li0.15Mn1.85]O4 oxygen anion redox reaction.

Li-rich compounds have received significant attention as electrode materials for lithium-ion batteries (LIBs) because of their large rechargeable capacities (qrecha). We have demonstrated a novel reaction scheme of one of the Li-rich compounds, Li[Li0.15Mn1.85]O4, where Mn4+ ions are reduced to lower valence states such as Mn3+ and Mn2+ ions during charging at voltages above 5.0 V.

Operando XAFS study of catalytic NO reduction over Cu/CeO2: the effect of copper-ceria interaction under periodic operation.

Using an operando time-resolved XAFS technique at the Cu and Ce K-edges, we have discovered that the synchronization of Cu and Ce valence change in Cu/CeO2 under periodic (rich-lean cycling) operation can improve the catalytic activity for NO reduction at low temperature.