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Abstract Photocatalytic CO2 reduction is considered as a promising strategy for CO2 utilization and producing renewable energy, however, it remains challenge in the improvement of photocatalytic performance for wide‐band‐gap photocatalyst with controllable product selectivity. Herein, the sulfur‐doped In(OH)3 (In(OH)xSy‐z) nanocubes are developed for selective photocatalytic reduction of CO2 to CH4 under simulated light irradiation. The CH4 yield of the optimal In(OH)xSy‐1.0 can be enhanced up to 39 times and the CH4 selectivity can be regulated as high as 80.75% compared to that of pristine In(OH)3. The substitution of sulfur atoms for hydroxyl groups in In(OH)3 enhances the visible light absorption capability, and further improves the hydrophilicity behavior, which promotes the H2O dissociation into protons (H*) and accelerates the dynamic proton‐feeding CO2 hydrogenation. In situ DRIFTs and DFT calculation confirm that the non‐metal sulfur sites significantly weaken the over‐potential of the H2O oxidation and prevent the formation of ·OH radicals, enabling the stabilization of *CHO intermediates and thus facilitating CH4 production. This work highlights the promotion effect of the non‐metal doping engineering on wide‐band‐gap photocatalysts for tailoring the product selectivity in photocatalytic CO2 reduction.

Surface frustrated Lewis pairs (SFLPs) provide a unique class of active sites that enable efficient gas-phase CO2 photocatalysis. How to tailor the reactivity of the SFLPs represents a major challenge, which the authors address here by single-site Bi3+ ion substitution of the SFLPs.

Abstract Nanostructured forms of stoichiometric In2O3 are proving to be efficacious catalysts for the gas-phase hydrogenation of CO2. These conversions can be facilitated using either heat or light; however, until now, the limited optical absorption intensity evidenced by the pale-yellow color of In2O3 has prevented the use of both together. To take advantage of the heat and light content of solar energy, it would be advantageous to make indium oxide black. Herein, we present a synthetic route to tune the color of In2O3 to pitch black by controlling its degree of non-stoichiometry. Black indium oxide comprises amorphous non-stoichiometric domains of In2O3-x on a core of crystalline stoichiometric In2O3, and has 100% selectivity towards the hydrogenation of CO2 to CO with a turnover frequency of 2.44 s−1.

Abstract Titanium dioxide is the only known material that can enable gas-phase CO2 photocatalysis in its anatase and rutile polymorphic forms. Materials engineering of polymorphism provides a useful strategy for optimizing the performance metrics of a photocatalyst. In this paper, it is shown that the less well known rhombohedral polymorph of indium sesquioxide, like its well-documented cubic polymorph, is a CO2 hydrogenation photocatalyst for the production of CH3OH and CO. Significantly, the rhombohedral polymorph exhibits higher activity, superior stability and improved selectivity towards CH3OH over CO. These gains in catalyst performance originate in the enhanced acidity and basicity of surface frustrated Lewis pairs in the rhombohedral form.

Phosphate (PO43-) modification of semiconductor photocatalysts such as TiO2, C3N4, BiVO4, and etc. has been shown positive effect on the enhancement of photocatalytic performance. In the present study, we demonstrate a novel one-pot surface modification route on Ag3PO4 photocatalyst by ammonium phosphate [(NH4)3PO4], which combines PO43- modification with ammonium (NH4+) etching to show multiple effects on the structural variation of Ag3PO4 samples. The modified Ag3PO4 photocatalysts exhibit much higher photocatalytic performance than bare Ag3PO4 for the degradation of organic dye solutions under visible light irradiation. It is indicated that the NH4+ etching favors the surface transition from Ag3PO4 to metallic Ag nanoparticles, resulting in the fast capture of photogenerated electrons and the followed generation of O2·− radicals. The strongly adsorbed PO43- on the Ag3PO4 surfaces can further provide more negative electrostatic field, which improves the separation of photogenerated electron-hole pairs by inducing the holes to directly flow to the surface and then enhances the formation of reactive ·OH radicals. Furthermore, the photocatalytic performance of the modified Ag3PO4 photocatalysts can be optimized by monitoring the concentration of (NH4)3PO4 that is 1 mM.

Abstract Supported atomically dispersed metals are proving to be efficacious photocatalysts for CO2 reduction to solar fuels. While being atom efficient, they suffer from being noble, rare, and costly (Pt, Pd, Au, Ag, Rh) and lacking in long‐term stability. Herein, all of these problems are solved with the discovery that atomically dispersed Cu supported on ultrathin TiO2 nanosheets can photocatalytically reduce an aqueous solution of CO2 to CO. The atomically dispersed Cu can be recycled in a straightforward procedure when they become oxidatively deactivated. This advance bodes well for the development of a solar fuels technology founded on abundant, low‐cost, nontoxic, atomically dispersed metal photocatalysts.

Regulating the electron-hole lifetime would increase the surface charge density of photocatalysts and then promote the photocatalytic conversion of CO2 into hydrocarbons. Herein, Pt and graphdiyne (GDY), respectively, as electron and hole transfer bodies were introduced into a multiple Pt/BiOBr-GDY heterojunction, constructing fast channels of electron and hole transfer and then prolonging their lifetime. Under light irradiation, the Pt/BiOBr-GDY nanocomposite changed the product distribution and significantly allowed the selective photocatalytic CO2 conversion to CH4 and C2 hydrocarbons (C2H4 and C2H6), with the total CxHy selectivity of about 97%. The synergistic effect of Pt and GDY facilitated the separation and transfer of photogenerated electrons and holes on BiOBr, increased the surface charge density, and ultimately improved the efficiency of photocatalytic CO2 reduction. At the same time, due to the characteristics of GDY, it can afford more surface-adsorbed active sites for CO2 and intermediates, thus further improving the photocatalytic efficiency and selectivity. Hence, this work provides an insight into the promotion of the selective photoreduction of CO2 to hydrocarbon products by the synergistic effect of the metal, semiconductor, and GDY. [ABSTRACT FROM AUTHOR]

The majority of bismuth containing oxides have been taken as important functional materials for applications including photocatalytic water splitting and highly conductive solid electrolytes, which however suffer from property degradation owing to the presence of intermediates. This work initiated a case study on α-Bi2O3nanoparticles with an aim to uncover the origin of property degradation when bismuth oxides that contain traces of secondary phase α-Bi2O3were exposed in either air or aqueous solutions. First, α-Bi2O3nanoparticles with spherical and rod-like morphologies were prepared by developing solution chemistries. It was found that α-Bi2O3transformed partially to Bi2O2CO3when stored in air for 6 months. Such transformation was further accelerated when α-Bi2O3nanoparticles were exposed to water or methylene blue (MB) solution, probably because α-Bi2O3reacts with the species HCO3−as formed by dissolution of CO2from air. Bi2O3surfaces had an unusual tendency to adsorb MB molecules, which in turn prevented the reaction between α-Bi2O3and HCO3−. Consequently, MB solution became clear even without light irradiation. The results reported in this work may help to fully comprehend the property degradation of bismuth containing oxides when used in aqueous solutions. [ABSTRACT FROM AUTHOR]

Rutile TiO2hierarchical microspheres were prepared by a facile solution chemistry method with an aim to achieve nanoscale boundary cavities (NBCs) that can be tailored for optimum giant dielectric performance. The formation of these microspheres proceeded viaa supersaturated spontaneous nucleation and a subsequent radial growth to develop into well-defined 3D hierarchical structures. All microspheres showed a diameter of about 8–10 μm and were constructed by small bundles that consisted of smaller nanowires with a diameter of 8–10 nm. These nanowires are characterized by a preferential growth along the [001] direction which eventually led to the externally exposed (110) planes for hierarchical microspheres. Strikingly, in between these constituent nanowires, there existed plenty of NBCs that created a great number of surface defect dipoles. The NBCs were further tailored by subsequent annealing of the microspheres, as clearly indicated by lattice contraction, linear increase of axis ratio, and red-shift of band-gap energy. As a consequence, rutile TiO2hierarchical microspheres showed an optimum giant permittivity of approximately 104level till 500 Hz at room temperature, compatible to the known giant-dielectric multicomponent materials such as CaCu3Ti4O12. These findings were rationalized in terms of NBCs and the resulting surface defect dipoles. As a reproductive prototype, tailoring of the NBCs in rutile hierarchical microspheres as reported in this work can be applied to a broad class of assembled nanostructures and probably film systems to modulate the dielectric performances for advanced electronic device aspects. [ABSTRACT FROM AUTHOR]

Nanosized porous In(OH)3 photocatalysts with high surface areas (as much as 110 m²∙g-1) were successfully synthesized by peptization of colloidal precipitates under ultrasound radiation. The resulting catalysts were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis, nitrogen adsorption, transition electron microscopy, and UV—vis diffuse reflection spectroscopy. The photocatalytic activities of the samples were evaluated by the gas-phase decomposition of several volatile organic pollutants (acetone, benzene, and toluene) under UV light illumination and were compared with that of the commercial titania (Degussa P25). Results revealed that the as-synthesized In(OH)3 exhibited much higher photocatalytic activity and durability than both In2O3 and TiO2. One, therefore, can conclude that nanosized In(OH)3 has potential application in environmental treatment, especially in the removal of benzene-containing exhaust emissions from shoemaking plants in China. The excellent photocatalytic performance of In(OH)3 can be attributed to its strong oxidation capability, abundant surface hydroxyl groups, and high BET surface area as well as the porous texture. [ABSTRACT FROM AUTHOR]

Pure cubic In2O3, orthorhombic InOOH and cubic In(OH)3nanocrystals were separately synthesized viaa one-pot aqueous solvothermal route at low temperature by simply regulating the amount of water in the ternary system H2O–DMF–In(NO3)3·4.5H2O. [ABSTRACT FROM AUTHOR]

Highly crystalline SnO2 nanocrystals with and without Zn2+ doping were directly prepared by a solvothermal method. By systematic characterizations using x-ray diffraction, transmission electron microscopy, infrared spectra, and UV-vis spectra, it is demonstrated that all samples crystallized in a single phase of rutile structure, and that upon Zn2+ doping particle sizes closer to the exciton Bohr radius (2.7 nm) of SnO2 were achieved, while the particle size of SnO2 nanoparticles was as large as about 12 nm without Zn2+ doping. The smaller particle sizes for Zn2+ doped nanoparticles had led to a lattice expansion, a blue-shift of the surface phonon mode for the anti-symmetric Sn-O stretching vibration, and a significantly narrowed band-gap energy, opposite to what is theoretically predicted by the quantum size effect. The photocatalytic activity of the doped samples is measured by monitoring the degradation of methylene blue dye in an aqueous solution under UV-radiation exposure. It is found that Zn2+ doped SnO2 showed excellent activity toward photodegradation of methylene blue solution under UV light irradiation. These observations were interpreted in terms of the Zn2+ doping at the surface sites of SnO2 nanoparticles and the relevant defects that have increased the surface active sites and moreover improved the ratio of surface charge carrier transfer rate to the electron-hole recombination rate. These results illustrate the potential of rationally modifying the particle size and surface defect characteristics for novel semiconductor oxide photocatalysts. [ABSTRACT FROM AUTHOR]