In situ electrochemical Raman spectroscopy and ab initio molecular dynamics study of interfacial water on a single-crystal surface

Amphipathic Surfactant on Reconstructed Bismuth Enables Industrial-Level Electroreduction of CO2 to Formate

Developing efficient electrocatalysts for selective formate production via the electrochemical CO2 reduction reaction (CO2RR) is challenged by high overpotential, a narrow potential window of high Faradaic efficiency (FEformate), and limited current density (Jformate). Herein, we report a hierarchical BiOBr (CT/h-BiOBr) with surface-anchored cetyltrimethylammonium bromide (CTAB) for formate-selective large-scale CO2RR electrocatalysis. CT/h-BiOBr achieves over 90% FEformate across a wide potential range (-0.5 to -1.1 V) and an industrial-level Jformate surpassing 100 mA·cm-2 at -0.7 V. In situ investigations uncover the reconstructed Bi(110) surface as the active phase, with CTAB playing a dual role: its hydrophobic alkyl chains create a CO2-enriching microenvironment, while its polar head groups fine-tune the electronic structure, fostering a highly active phase. This work provides valuable insights into the role of surfactants in electrocatalysis and guides the design of electrocatalysts for the large-scale CO2RR.

Mechanistic Insights into Surfactant-Modulated Electrode-Electrolyte Interface for Steering H2O2 Electrosynthesis

Electrocatalytic reactions taking place at the electrified electrode-electrolyte interface involve processes of proton-coupled electron transfer. Interfacial protons are delivered to the electrode surface via a H2O-dominated hydrogen-bond network. Less efforts are made to regulate the interfacial proton transfer from the perspective of interfacial hydrogen-bond network. Here, we present quaternary ammonium salt cationic surfactants as electrolyte additives for enhancing the H2O2 selectivity of the oxygen reduction reaction (ORR). Through in situ vibrational spectroscopy and molecular dynamics calculation, it is revealed that the surfactants are irreversibly adsorbed on the electrode surface in response to a given bias potential range, leading to the weakening of the interfacial hydrogen-bond network. This decreases interfacial proton transfer kinetics, particularly at high bias potentials, thus suppressing the 4-electron ORR pathway and achieving a highly selective 2-electron pathway toward H2O2. These results highlight the opportunity for steering H2O-involved electrochemical reactions via modulating the interfacial hydrogen-bond network.

Cation-Induced Interfacial Hydrophobic Microenvironment Promotes the C-C Coupling in Electrochemical CO2 Reduction

The electrochemical carbon dioxide reduction reaction (CO2RR) toward C2 products is a promising way for the clean energy economy. Modulating the structure of the electric double layer (EDL), especially the interfacial water and cation type, is a useful strategy to promote C-C coupling, but atomic understanding lags far behind the experimental observations. Herein, we investigate the combined effect of interfacial water and alkali metal cations on the C-C coupling at the Cu(100) electrode/electrolyte interface using ab initio molecular dynamics (AIMD) simulations with a constrained MD and slow-growth approach. We observe a linear correlation between the water-adsorbate stabilization effect, which manifests as hydrogen bonds, and the corresponding alleviation in the C-C coupling free energy. The role of a larger cation, compared to a smaller cation (e.g., K+ vs Li+), lies in its ability to approach the interface through desolvation and coordinates with the *CO+*CO moiety, partially substituting the hydrogen-bonding stabilizing effect of interfacial water. Although this only results in a marginal reduction of the energy barrier for C-C coupling, it creates a local hydrophobic environment with a scarcity of hydrogen bonds owing to its great ionic radius, impeding the hydrogen of surrounding interfacial water to approach the oxygen of the adsorbed *CO. This skillfully circumvents the further hydrogenation of *CO toward the C1 pathway, serving as the predominant factor through which a larger cation facilitates C-C coupling. This study unveils a comprehensive atomic mechanism of the cation-water-adsorbate interactions that can facilitate the further optimization of the electrolyte and EDL for efficient C-C coupling in CO2RR.

CoIn dual-atom catalyst for hydrogen peroxide production via oxygen reduction reaction in acid

The two-electron oxygen reduction reaction in acid is highly attractive to produce H2O2, a commodity chemical vital in various industry and household scenarios, which is still hindered by the sluggish reaction kinetics. Herein, both density function theory calculation and in-situ characterization demonstrate that in dual-atom CoIn catalyst, O-affinitive In atom triggers the favorable and stable adsorption of hydroxyl, which effectively optimizes the adsorption of OOH on neighboring Co. As a result, the oxygen reduction on Co atoms shifts to two-electron pathway for efficient H2O2 production in acid. The H2O2 partial current density reaches 1.92 mA cm-2 at 0.65 V in the rotating ring-disk electrode test, while the H2O2 production rate is as high as 9.68 mol g-1 h-1 in the three-phase flow cell. Additionally, the CoIn-N-C presents excellent stability during the long-term operation, verifying the practicability of the CoIn-N-C catalyst. This work provides inspiring insights into the rational design of active catalysts for H2O2 production and other catalytic systems.