In situ probing the dynamic reconstruction of copper-zinc electrocatalysts for CO2 reduction.

Unravelling the dynamic characterization of electrocatalysts during the electrochemical CO2 reduction reaction (CO2RR) is a critical factor to improve the production efficiency and selectivity, since most pre-electrocatalysts undergo structural reconstruction and surface rearrangement under working conditions. Herein, a series of pre-electrocatalysts including CuO, ZnO and two different ratios of CuO/ZnO were systematically designed by a sputtering process to clarify the correlation of the dynamic characterization of Cu sites in the presence of Zn/ZnO and the product profile. The evidence provided by in situ X-ray absorption spectroscopy (XAS) indicated that appropriate Zn/ZnO levels could induce a variation in the coordination number of Cu sites via reversing Ostwald ripening. Specifically, the recrystallized Cu site with a lower coordination number exhibited a preferential production of methane (CH4). More importantly, our findings provide a promising approach for the efficient production of CH4 by in situ reconstructing Cu-based binary electrocatalysts.

In Situ Identifying the Dynamic Structure behind Activity of Atomically Dispersed Platinum Catalyst toward Hydrogen Evolution Reaction.

Single-atom catalysts (SAs) with the maximum atom utilization and breakthrough activities toward hydrogen evolution reaction (HER) have attracted considerable research interests. Uncovering the nature of single-atom metal centers under operating electrochemical condition is highly significant for improving their catalytic performance, yet is poorly understood in most studies. Herein, Pt single atoms anchoring on the nitrogen-carbon substrate (PtSA /N-C) as a model system are utilized to investigate the dynamic structure of Pt single-atom centers during the HER process. Via in situ/operando synchrotron X-ray absorption spectroscopy and X-ray photoelectron spectroscopy, an intriguing structural reconstruction at atomic level is identified in the PtSA /N-C when it is subjected to the repetitive linear sweep voltammetry and cyclic voltammetry scanning. It demonstrates that the PtN bonding tends to be weakened under cathodic potentials, which induces some Pt single atoms to dynamically aggregate into forming small clusters during the HER reaction. More importantly, experimental evidence and/or indicator is offered to correlate the observed Tafel slope with the dynamic structure of Pt catalysts. This work provides an evident understanding of SAs under electrocatalytic process and offers informative insights into constructing efficient catalysts at atomic level for electrochemical water-splitting system.

In situ unraveling of the effect of the dynamic chemical state on selective CO2 reduction upon zinc electrocatalysts.

Unraveling the reaction mechanism behind the CO2 reduction reaction (CO2RR) is a crucial step for advancing the development of efficient and selective electrocatalysts to yield valuable chemicals. To understand the mechanism of zinc electrocatalysts toward the CO2RR, a series of thermally oxidized zinc foils is prepared to achieve a direct correlation between the chemical state of the electrocatalyst and product selectivity. The evidence provided by in situ Raman spectroscopy, X-ray absorption spectroscopy (XAS) and X-ray diffraction significantly demonstrates that the Zn(ii) and Zn(0) species on the surface are responsible for the production of carbon monoxide (CO) and formate, respectively. Specifically, the destruction of a dense oxide layer on the surface of zinc foil through a thermal oxidation process results in a 4-fold improvement of faradaic efficiency (FE) of formate toward the CO2RR. The results from in situ measurements reveal that the chemical state of zinc electrocatalysts could dominate the product profile for the CO2RR, which provides a promising approach for tuning the product selectivity of zinc electrocatalysts.

In Situ Creation of Surface-Enhanced Raman Scattering Active Au-AuO x Nanostructures through Electrochemical Process for Pigment Detection.

Roughing the metallic surface via oxidation-reduction cycles (ORC) to integrate the surface plasmon resonance and surface-enhanced Raman scattering (SERS) is predominant in developing sensor systems because of the facile preparation and uniform distribution of nanostructures. Herein, we proposed a distinctive ORC process: the forward potential passed through the oxidation of Au and reached the oxygen evolution reaction, and once the potential briefly remained at the vertex, the various reverse rates were employed to control the reduction state. The created hybrid Au-AuO x possessed electromagnetic and chemical enhancements concurrently, wherein the rough surface provided the strong local electromagnetic fields and significant interaction between AuO x and molecule to improve the charge transfer. The synergistic effects significantly amplified the intensity of Raman signal with an enhancement factor of 5.5 × 106 under the optimal conditions. Furthermore, the prepared SERS substrate can simultaneously identify and quantify the mixed edible pigments, Brilliant Blue FCF and Indigo Carmine, individually. This result suggested that the development of SERS sensor based on the proposed SERS-activated methodology is feasible and reliable.