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Perovskite oxide SrTiO 3 is a promising semiconductor photocatalyst for CO 2 reduction, which has two possible chemical surfaces—TiO 2 -terminated and SrO-terminated surfaces. Up to now, the effect of chemical surface and its modification on CO 2 adsorption, activation and sequential photocatalytic reduction is not established. In the work, SrTiO 3 , surface-Ti-rich SrTiO 3 and Sr(OH) 2 -decorated SrTiO 3 were prepared and their structural, surface, and optical properties and photocatalytic activity were explored. It is found that the absorption edge of surface-Ti-rich SrTiO 3 shifted toward visible-light region as compared with that of the other two photocatalysts, which is attributed to the decreased Ti 3d ground-state level at the surface. Bicarbonate- (HCO 3 − ) and bidentate carbonate-like (b-CO 3 = ) species are the main species for CO 2 adsorption on the surface-Ti-rich SrTiO 3 , whereas, besides HCO 3 − and b-CO 3 = , plenty of monodentate carbonate-like species (m-CO 3 = ) that has relatively low reactivity is present on the SrTiO 3 and Sr(OH) 2 -decorated photocatalysts. As a result, the surface-Ti-rich SrTiO 3 exhibits the highest activity for CO 2 reduction. Furthermore, although Sr(OH) 2 -decoration and SrO-terminated surfaces facilitate CO 2 fixing, the produced surface species are attached to the weakly active Sr ions, giving rise to the lower reactivity. The present work might supply a guide for designing highly active perovskite–type semiconductors for photocatalysis. [ABSTRACT FROM AUTHOR]

α-Fe 2 O 3 /BiOCl heterojunctions were synthesized by growing and assembling α-Fe 2 O 3 nanoplates to BiOCl microflowers via a two-step route to enhance the photocatalytic performance of BiOCl. The morphology, microstructure, element composition and optical properties of α-Fe 2 O 3 /BiOCl heterojunctions have been investigated by SEM, TEM, XRD, FT-IR, Raman spectra, XPS, UV–vis diffuse reflectance and PL spectra. Electrostatic interaction was a key to form α-Fe 2 O 3 /BiOCl heterojunctions. Compared with pure BiOCl, the synthesized α-Fe 2 O 3 /BiOCl heterojunctions possess an efficient visible light absorption and exhibit an improved of photocatalytic efficiency. A photocatalytic degradation mechanism has been proposed to explain that the heterojunctions enhance the separation efficiency of electron-hole pairs, and the holes are the main reactive species in the degratation of Rhodamine B. [ABSTRACT FROM AUTHOR]

The SrBi 2 Nb 2 O 9 platelets with a thickness of about 600 nm were synthesized by molten salt synthesis method. The treatment of the SrBi 2 Nb 2 O 9 platelets with hydrochloric acid resulted in the formation of the protonated H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 platelets. Through a top–down approach in ethylamine solution, the H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 platelets were exfoliated into H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 nanosheets with a thickness of about 2.6 nm. The evolution of the structure, composition, morphology, optical, and photocatalytic properties of SrBi 2 Nb 2 O 9 platelets was studied as it is converted into H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 platelets and subsequently exfoliated into H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 nanosheets. The absorption edge shifts to a lower wavelength accompanied by the protonation and exfoliation. The photocatalytic H 2 evolution of the three samples were evaluated under the irradiation of a 300 W Xenon lamp from CH 3 OH/H 2 O solution, indicating that H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 nanosheets Exhibit 5.5 and 26.2 times higher activity than that of the H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 and SrBi 2 Nb 2 O 9 platelets, respectively. The enhanced activity for the H 1.78 Sr 0.78 Bi 0.22 Nb 2 O 7 nanosheets is mainly attributed to the higher separation efficiency of the photogenerated carriers and the larger specific surface area caused by the significant reduction in thickness. [ABSTRACT FROM AUTHOR]

• N-doped TiO 2 @rGO nanotubes were prepared by annealing GO-coated H-titanate nanotubes in ammonia. • The composite absorbs nearly the full visible-light spectrum. • Without Pt as a cocatalyst, the H 2 production rate is as high as 720 µmol g−1 h−1. • Even one year, the surface Ti3+'s concentration exhibits no distinct decrease. Due to the merits of visible-light absorption and high conductivity, Ti3+ is a main focus among the modifications of TiO 2. However, surface Ti3+ is unstable. Herein, surface-stable Ti3+ in an N-doped rGO-coated TiO 2 nanotube sample is prepared. The N-doping introduced Ti-C bonds and an abundance of surface Ti3+, which produced several mid-gap states. These properties allow the composite to absorb nearly the full visible-light spectrum. Owing to the advantages of a broad visible-light absorption, short diffusion distance in the nanotube, and a good heterojunction, the composite exhibits a good photocatalytic activity. Under visible light and without Pt as a cocatalyst, methylene blue was degraded within 40 mins, and the H 2 production rate is as high as 720 µmol g−1 h−1. Due to the synergistic effect of N doping and Ti-C bond formation, the configuration of surface Ti3+ is stabilized by a charge-transfer resonance mechanism. The tightly coated graphene also plays a vital role in protecting the surface Ti3+. Even after storage for one year, the photocatalytic activity and the EPR signal intensity from Ti3+ paramagnetic states remain unchanged within experimental error. It suggests that the surface Ti3+ concentration, and the properties of the composite are stable with time. [ABSTRACT FROM AUTHOR]