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The substantial overpotential of CO2 activation, the complex CO2 reduction pathway, and the competitive H2 evolution reaction (HER) limit the practical applications of CO2-based electrochemical energy conversion and storage technologies due to their low energy efficiency and product selectivity. Here, we proposed a strategy that combines mesopores and redox-active couple to effectively capture CO2 and selectively generate CO product. As an example, we construct a redox-active couple, Zn2+/Zn+, on the low-crystallinity mesoporous ZnGa2O4 electrocatalyst. The mesopores not only help to capture CO2 effectively but also inhibit the H2 evolution. The weak lattice constraint of low crystallinity benefits the formation of a Zn2+/Zn+ redox couple to strongly interact with CO2 molecule for subsequent activation and catalytic conversion, thus effectively decreasing the activation energy of CO2 to the active species CO2− and accelerating the proton transfer to form the crucial COOH* intermediate. Consequently, this catalyst exhibited a high faradaic efficiency of 96% among Zn-based electrodes for CO generation at the relatively low applied potential of −1.4 V vs. Ag/AgCl (−0.8 V vs. RHE), and excellent stability during 10 h operation in a 0.1 M KHCO3 solution. [ABSTRACT FROM AUTHOR]

Self-doping by Ti3+ is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti3+-doped TiO2 seems to be a challenge due to the easy oxidation of Ti3+ during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti3+-doped TiO2, in which both the Ti3+ and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti3+-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti3+ in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response. [ABSTRACT FROM AUTHOR]

A challenge in electrochemical CO 2 reduction is inhibiting hydrogen evolution reaction (HER). Herein, a bulk Zn electrode was chosen to reveal the effect of specifically adsorbed Cl - ions on HER during CO 2 reduction. We found that in the Cl - ion-containing electrolyte, the Zn-Cl adlayer formed because the weakly solvated Cl - ions can strip the solvation shell and form a direct chemical bond with the metal Zn. As a result, the Zn-Cl bonds on the Zn electrode notably blocked the hydrogen evolution and significantly facilitated the electron transfer process via the Cl to the vacant orbitals of inert CO 2 , therefore stabilizing the CO 2 - radical and leading to a four times higher CO Faradaic efficiency for CO 2 reduction in the KCl electrolyte than that in the KHCO 3 electrolyte at a moderate potential of -1.2 V versus a reversible hydrogen electrode.

Here, we discover that there is an electrochemical doping reaction that generates surface states when TiO2 nanotube photoanodes are immersed into NaBH4 solution, thus improving the photoelectrochemical performance due to the surface states acting as an efficient electron transfer route.

Sluggish water dissociation kinetics on nonprecious metal electrocatalysts limits the development of economical hydrogen production from water-alkali electrolyzers. Here, using Co 3 N electrocatalyst as a prototype, we find that during water splitting in alkaline electrolyte a cobalt-containing hydroxide formed on the surface of Co 3 N, which greatly decreased the activation energy of water dissociation (Volmer step, a main rate-determining step for water splitting in alkaline electrolytes). Combining the cobalt ion poisoning test and theoretical calculations, the efficient hydrogen production on Co 3 N electrocatalysts would benefit from favorable water dissociation on in-situ formed cobalt-containing hydroxide and low hydrogen production barrier on the nitrogen sites of Co 3 N. As a result, the Co 3 N catalyst exhibits a low water-splitting activation energy (26.57 kJ mol -1 ) that approaches the value of platinum electrodes (11.69 kJ mol -1 ). Our findings offer new insight into understanding the catalytic mechanism of nitride electrocatalysts, thus contributing to the development of economical hydrogen production in alkaline electrolytes.