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A challenge in electrochemical CO2reduction 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 CO2reduction. 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 CO2, therefore stabilizing the CO2–radical and leading to a four times higher CO Faradaic efficiency for CO2reduction in the KCl electrolyte than that in the KHCO3electrolyte at a moderate potential of −1.2 V versus a reversible hydrogen electrode.

Adding charge scavengers, which usually are more unstable than water, is an effective method to quantify the quantum efficiency loss of photoelectrode during the charge separation, transfer, and injection processes of the water splitting reaction. Here, we detected, on TiO2nanotube photoanodes after using hydrogen peroxide (H2O2) as a hole scavenger, a nearly 40% saturated photocurrent decrease in alkaline electrolyte and a negligible saturated photocurrent difference in acid electrolyte. We found that the photoelectrons were trapped in the surface states of TiO2with nearly the same storage capacity of electrons in a wide range of pH values from 1.0 to 13.6. However, kinetics of a back reaction, H2O2reduction by the photoelectrons trapped in surface states, is about 10 times higher for that in alkaline electrolyte than in acid electrolyte. As a result, the pH-dependent kinetic difference in H2O2reduction induced the negative effects on the saturated photocurrent. Our results offer a new insight into understanding the effects of back electron transfer on electrochemical behaviors of surface states and charge scavengers.

Photothermal catalysis, which combines light promotion and thermal activation, is a promising approach for converting CO2into fuels. However, the development of photothermal catalysts with effective light-to-heat conversion, strong charge transfer ability, and suitable active sites remains a challenge. Herein, the photothermal effect- and interfacial N–Ni/Ta–O bond-modulated heterostructure composed of oxygen vacancy-rich NiOxand Ta3N5was rationally fabricated for efficient photothermal catalytic CO2reduction. Beyond the charge separation capability conferred by the NiOx/Ta3N5heterojunction, we observed that the N–Ni and Ta–O bonds linking NiOxand Ta3N5form a spatial charge transfer channel, which enhances the interfacial electron transfer. Additionally, the presence of surface oxygen vacancies in NiOxinduced nonradiative relaxation, resulting in a pronounced photothermal effect that locally heated the catalyst and accelerated the reaction kinetically. Leveraging these favorable factors, the NiOx/Ta3N5hybrids exhibit remarkably elevated activity (≈32.3 μmol·g–1·h–1) in the conversion of CO2to CH4with near-unity selectivity, surpassing the performance of bare Ta3N5by over 14 times. This study unveils the synergistic effect of photothermal and interfacial chemical bonds in the photothermal–photocatalytic heterojunction system, offering a novel approach to enhance the reaction kinetics of various catalysts.

Uniform hierarchical microspheres scaffolded from ultrathin ZnGa2O4nanosheets with over 99% exposed facets were synthesized using an easy solvothermal route with ethylenediamine (en)/H2O binary solvents. Substitution of different chain length amines for en results in no formation of the nanosheet structures, indicating that the molecular structure of En is indispensable for the generation of two-dimensional structures. Inheriting both a high surface area of nanosheets and a high crystallinity of bulky materials allows the unique 3D hierarchical nanostructures to possess great CO2photocatalytic performance. The normalized time-resolved traces of photo-induced absorption recorded from the nanosheet and meso-ZnGa2O4indicate that the photo-excited carriers can survive longer on the nanosheet, which also contributes to the high photocatalytic activity of the ZnGa2O4nanosheets.

Ultrathin and uniform Bi2WO6square nanoplates of ∼9.5 nm thickness corresponding to six repeating cell units were prepared in the presence of oleylamine using a hydrothermal route. The Bi2WO6nanoplates show great potential in the utilization of visible light energy to the highly efficient reduction of CO2into a renewable hydrocarbon fuel. On the one hand, the ultrathin geometry of the nanoplates promotes charge carriers to move rapidly from the interior to the surface to participate in the photoreduction reaction. This should also favor the improved separation of photogenerated electron and hole and a lower electron–hole recombination rate; on the other hand, the Bi2WO6square nanoplate is proven to provide the well-defined {001} facet for two dominantly exposed surfaces, which is a prerequisite for the high level of photocatalytic activity of CO2fixation.