The electrocatalytic carbon dioxide (CO₂) reduction reaction (CO₂RR) into hydrocarbons is a promising approach for greenhouse gas mitigation, but many details of this dynamic reaction remain elusive. Here, time‐resolved surface‐enhanced Raman spectroscopy (TR‐SERS) is employed to successfully monitor the dynamics of CO₂RR intermediates and Cu surfaces with sub‐second time resolution. Anodic treatment at 1.55 V vs. RHE and subsequent surface oxide reduction (below −0.4 V vs. RHE) induced roughening of the Cu electrode surface, which resulted in hotspots for TR‐SERS, enhanced time resolution (down to ≈0.7 s) and fourfold improved CO₂RR efficiency toward ethylene. With TR‐SERS, the initial restructuring of the Cu surface was followed (<7 s), after which a stable surface surrounded by increased local alkalinity was formed. Our measurements revealed that a highly dynamic CO intermediate, with a characteristic vibration below 2060 cm⁻¹, is related to C−C coupling and ethylene production (−0.9 V vs. RHE), whereas lower cathodic bias (−0.7 V vs. RHE) resulted in gaseous CO production from isolated and static CO surface species with a distinct vibration at 2092 cm⁻¹.

Molybdenum disulfide (MoS₂) and related transition metal chalcogenides can replace expensive precious metal catalysts such as Pt for the hydrogen evolution reaction (HER). The relations between the nanoscale properties and HER activity of well‐controlled 2H and Li‐promoted 1T phases of MoS₂, as well as an amorphous MoS₂ phase, have been investigated and a detailed comparison is made on Mo−S and Mo−Mo bond analysis under operando HER conditions, which reveals a similar bond structure in 1T and amorphous MoS₂ phases as a key feature in explaining their increased HER activity. Whereas the distinct bond structure in 1T phase MoS₂ is caused by Li⁺ intercalation and disappears under harsh HER conditions, amorphous MoS₂ maintains its intrinsic short Mo−Mo bond feature and, with that, its high HER activity. Quantum‐chemical calculations indicate similar electronic structures of small MoS₂ clusters serving as models for amorphous MoS₂ and the 1T phase MoS₂, showing similar Gibbs free energies for hydrogen adsorption (ΔG_H*) and metallic character.

Oxide-derived copper electrodes have displayed a boost in activity and selectivity toward valuable base chemicals in the electrochemical carbon dioxide reduction reaction (CO2RR), but the exact interplay between the dynamic restructuring of copper oxide electrodes and their activity and selectivity is not fully understood. In this work, we have utilized time-resolved surface-enhanced Raman spectroscopy (TR-SERS) to study the dynamic restructuring of the copper (oxide) electrode surface and the adsorption of reaction intermediates during cyclic voltammetry (CV) and pulsed electrolysis (PE). By coupling the electrochemical data to the spectral features in TR-SERS, we study the dynamic activation of and reactions on the electrode surface and find that CO₂ is already activated to carbon monoxide (CO) during PE (10% Faradaic efficiency, 1% under static applied potential) at low overpotentials (-0.35 V_RHE). PE at varying cathodic bias on different timescales revealed that stochastic CO is dominant directly after the cathodic bias onset, whereas no CO intermediates were observed after prolonged application of low overpotentials. An increase in cathodic bias (-0.55 V_RHE) resulted in the formation of static adsorbed CO intermediates, while the overall contribution of stochastic CO decreased. We attribute the low-overpotential CO₂-to-CO activation to a combination of selective Cu(111) facet exposure, partially oxidized surfaces during PE, and the formation of copper-carbonate-hydroxide complex intermediates during the anodic pulses. This work sheds light on the restructuring of oxide-derived copper electrodes and low-overpotential CO formation and highlights the power of the combination of electrochemistry and time-resolved vibrational spectroscopy to elucidate CO2RR mechanisms.

A low-temperature plasma enhanced atomic layer deposition process is demonstrated to synthesize high quality 2-D MoS ₂ films with tuneable morphology.

Au-Cu bimetallic thin films with controlled composition were fabricated by magnetron sputtering co-deposition, and their performance for the electrocatalytic reduction of CO2 was investigated. The uniform planar morphology served as a platform to evaluate the electronic effect isolated from morphological effects while minimizing geometric contributions. The catalytic selectivity and activity of Au-Cu alloys was found to be correlated with the variation of electronic structure that was varied with tunable composition. Notably, the d-band center gradually shifted away from the Fermi level with increasing the Au atomic ratio, leading to a weakened binding energy of *CO, which is consistent with low CO coverage observed in CO stripping experiments. The decrease of the *CO binding strength results in the enhanced catalytic activity for CO formation with the increase of Au content. In addition, it was observed that copper oxide/hydroxide species are less stable on Au-Cu surfaces compared to those on pure Cu surface, where the surface oxophilicity could be critical to tuning the binding strength of *OCHO. These results imply that the altered electronic structure could explain the decreased formation of HCOO─ on these alloys. In general, the formation of CO and HCOO─ as main CO2 reduction products on planar Au-Cu alloys followed the shift of d-band center, which indicates the electronic effect is the major governing factor for the electrocatalytic activity of CO2 reduction on Au-Cu bimetallic thin films.