An oxidized copper species (Cuδ+) on the metallic copper surface is critical to the activity and selectivity of electrochemical reduction of CO2 gas. However, Cuδ+ species are easily reduced under working conditions of CO2 electroreduction. Herein, we propose an interface engineering strategy to stabilize Cuδ+ species; specifically, ZnO x nanoparticles are grown on a copper foil to generate a Cu/ZnO x interface. The interface stabilizes the surface Cu2+ species and delivers high methane selectivity (∼36%) and long-term durability (>12 h) at a potential of −1.1 V versus reversible hydrogen electrode (RHE) for CO2 reduction. By combining comprehensive characterizations with simulation experiments, we identify cupric species as active sites for CH4 formation, which is confirmed by density functional theory calculations. Our work demonstrates that interface engineering is a promising way to stabilize active sites and boost selective CO2 electroreduction.

The electrocatalytic hydrogen evolution reaction (HER) of a given metal catalyst is intrinsically related to its electronic structure, which is difficult to alter for further improvement. Recently, it was discovered that the density of grain boundaries (GBs) is mechanistically of great importance for catalytic activity, implying that GBs are quantitatively correlated with the active sites in the HER. Here, by modeling the atomistic structure of GBs on a Au(110) surface, we find that HER performance is greatly enhanced by Au GBs, suggesting the feasibility of the HER mediated by GBs. The promoted HER performance is due to an increase in the capability of binding adsorbed hydrogen on the sites around GBs. A Au catalyst with a dominantly exposed (110) plane is synthesized, where considerable GBs exist for experimental verification. It is found that HER activity is inherently correlated with the density of the GBs in Au NPs. The improvement in HER activity can be elucidated from the geometrical and electronic points of view; the broken local spatial symmetry near a GB causes a decrease in the coordination numbers of the surface sites and the shift up of the d–band center, thereby reducing the limiting potential for each proton−electron transfer step. Our finding represents a promising means to further improve the HER activity of a catalyst.

Work function can serve as a characteristic quantity to evaluate the catalytic activity due to the relation with the surface structure of a materials. However, what factors determine the influence...

Metal-organic frameworks (MOFs) are considered to be the most promising positive anode materials to store charge for electrochromic devices. Nevertheless, a detailed mechanism of the electrochemical and ions storage process has not yet been revealed. Herein, the electrochemical mechanism of the highly porous ZIF-67 films and the electrochromic performance of electrochromic mirrors constructed from ZIF-67 and WO3 electrodes were investigated. The mechanism of the charge storage was revealed in the kinetic analysis of the Li-ion behavior based on the cyclic voltammetry curves and electrochemical impedance spectra. Impressively, the electrochromic mirrors with the self-bleaching effect and self-discharge behavior showed a unique electrochromic performance, such as a high coloration efficiency of 16.47 cm2 C−1 and a maximum reflectance modulation of 30.10% at 650 nm. This work provides a fundamental understanding of MOFs for applications in electrochromic devices and can also promote the exploration of novel electrode materials for high-performance reflective electrochromic devices.

It is a great challenge to synthesize efficient electrocatalysts for overall water splitting, especially non-noble metal catalysts. Herein, one-dimensional polycrystalline nanoneedles composed of CoOÀ Co 9 S 8 nano heterostructures, in situ grown on carbon fiber paper are prepared for efficient overall water electrolysis. Due to strong electronic coupling, charge densities of Co 2 + / Co 3 + in Co 9 S 8 and Co 2 + in CoO are favorably modified at the interface of CoO and Co 9 S 8 , resulting in optimized reaction intermediates absorption and greatly enhanced bifunctional HER/OER activities. CoOÀ Co 9 S 8 /CFP delivers a current density of 10 mA cm À 2 in alkaline electrolyte at overpotentials of 184 mV and 270 mV for HER and OER, respectively. When used as electrocatalyst for overall water splitting, it needs a low cell potential of 1.66 V to realize water electrolysis at 10 mA cm À 2 . This work provides a new strategy to tune the electronic structures of transitional metal active sites via constructing nano heterostructures for efficient water electrolysis.