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Photocatalytic CO2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C3N4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C3N4, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C3N4/rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs3Bi2Br9, resulting in a g-C3N4/rGO/Cs3Bi2Br9 composite. This leads to a remarkable increase in photocatalytic conversion of CO2 and H2O to CO, H2 and CH4 at rates of 54.3 (±2.0) μmole− g−1 h−1, surpassing that of pure Cs3Bi2Br9 (11.2 ± 0.4 μmole− g−1 h−1) and bulk g-C3N4 (5.5 ± 0.5 μmole− g−1 h−1). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C3N4 and Cs3Bi2Br9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs3Bi2Br9) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C3N4) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals. [ABSTRACT FROM AUTHOR]

Multicompound TiO2/SiO2 nanoparticles with a diameter of 50–70 nm were generated using a liquid flame spray (LFS) nanoparticle deposition in a single flame. Here, we study the photocatalytic activity of deposited multicompound nanoparticles in gas-phase via oxidation of acetylene into carbon dioxide that gives new insight about the multicompound nanoparticle morphology. A small addition of SiO2 content of 0.5%, 1.0% and 3.0% significantly suppressed the photocatalytic activity by 33%, 44% and 70%, respectively, whereas 5.0% SiO2 addition completely removed the activity. This may be due to a formation of a thin passivating SiO2 layer on top of the of the TiO2 nanostructures during the LFS nanoparticle deposition. Surface wetting results support this hypothesis with a significant increase in water contact angle as the SiO2 content is increased. [ABSTRACT FROM AUTHOR]

Photocatalytic CO 2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C 3 N 4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C 3 N 4 , which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C 3 N 4 /rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs 3 Bi 2 Br 9 , resulting in a g-C 3 N 4 /rGO/Cs 3 Bi 2 Br 9 composite. This leads to a remarkable increase in photocatalytic conversion of CO 2 and H 2 O to CO, H 2 and CH 4 at rates of 54.3 (±2.0) μmol e - g -1 h -1 , surpassing that of pure Cs 3 Bi 2 Br 9 (11.2 ± 0.4 μmol e - g -1 h -1 ) and bulk g-C 3 N 4 (5.5 ± 0.5 μmol e - g -1 h -1 ). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C 3 N 4 and Cs 3 Bi 2 Br 9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs 3 Bi 2 Br 9 ) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C 3 N 4 ) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO 2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Cu 3 TeO 6 (CTO) has been synthesized by hydrothermal synthesis applying different pH values without any template or a calcination step to control the crystalline phase and the morphology of nanoparticles. The physicochemical properties characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, N 2 adsorption, X-ray photoelectron spectroscopy, and diffuse reflectance ultraviolet-visible (DRUV-vis) spectroscopy techniques revealed that the pH values significantly influence the crystal growth. In acidic media (pH = 2), crystal growth has not been achieved. At pH = 4, the yield is low (10%), and the CTO presents irregular morphology. At pH = 6, the yield increases (up to 71%) obtaining an agglomeration of nanoparticles into spherical morphology. At basic conditions (pH = 8), the yield increases up to 90% and the morphology is the same as the sample obtained at pH = 6. At high basic conditions (pH = 10), the yield is similar (92%), although the morphology changes totally to dispersed nanoparticles. Importantly, the as-prepared CTO semiconductor presents photocatalytic activity for H 2 production using triethanolamine as a sacrificial agent under visible light illumination. The results also revealed that the nanoparticles agglomerated in a spherical morphology with larger surface area presented almost double activities in H 2 production compared to heterogeneously sized particles. These results highlight the suitable optoelectronic properties, including optical band gap, energy levels, and photoconductivity of CTO semiconductors for their use in photocatalytic H 2 production., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Lead-free halide perovskite derivative Cs 3 Bi 2 Br 9 has recently been found to possess optoelectronic properties suitable for photocatalytic CO 2 reduction reactions to CO. However, further work needs to be performed to boost charge separation for improving the overall efficiency of the photocatalyst. This report demonstrates the synthesis of a hybrid inorganic/organic heterojunction between Cs 3 Bi 2 Br 9 and g-C 3 N 4 at different ratios, achieved by growing Cs 3 Bi 2 Br 9 crystals on the surface of g-C 3 N 4 using a straightforward antisolvent crystallization method. The synthesized powders showed enhanced gas-phase photocatalytic CO 2 reduction in the absence of hole scavengers of 14.22 (±1.24) μmol CO g -1 h -1 with 40 wt % Cs 3 Bi 2 Br 9 compared with 1.89 (±0.72) and 5.58 (±0.14) μmol CO g -1 h -1 for pure g-C 3 N 4 and Cs 3 Bi 2 Br 9 , respectively. Photoelectrochemical measurements also showed enhanced photocurrent in the 40 wt % Cs 3 Bi 2 Br 9 composite, demonstrating enhanced charge separation. In addition, stability tests demonstrated structural stability upon the formation of a heterojunction, even after 15 h of illumination. Band structure alignment and selective metal deposition studies indicated the formation of a direct Z-scheme heterojunction between the two semiconductors, which boosted charge separation. These findings support the potential of hybrid organic/inorganic g-C 3 N 4 /Cs 3 Bi 2 Br 9 Z-scheme photocatalyst for enhanced CO 2 photocatalytic activity and improved stability., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

TiO 2 inverse opal (TIO) structures were prepared by the conventional wet chemical method, resulting in well-formed structures for photocatalytic activity. The obtained structures were functionalized with liquid flame spray-deposited silver nanoparticles (AgNPs). The nanocomposites of TIO and AgNPs were extensively characterized by various spectroscopies such as UV, Raman, X-ray diffraction, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy combined with microscopic methods such as scanning electron microscopy, transmission electron microscopy (TEM), and high-resolution TEM. The characterization confirmed that high-quality heterostructures had been fabricated with evenly and uniformly distributed AgNPs. Fabrication of anatase TiO 2 was confirmed, and formation of AgNPs was verified with surface plasmon resonant properties. The photocatalytic activity results measured in the gas phase showed that deposition of AgNPs increases photocatalytic activity both under UVA and visible light excitation; moreover, enhanced hydrogen evolution was demonstrated under visible light.

Three-dimensional highly ordered multilayer titanium dioxide (TiO 2 ) inverse opal (TIO) structures with two pore sizes were fabricated over a large surface using a self-convective method. The fabricated TIO multilayers were functionalized with gold nanoparticles (AuNPs) by immersing the samples in solution with gold nanoparticles. The photocatalytic activity of TiO 2 was enhanced by 85% via plasmonic activation of AuNPs that increased the lifetime of photogenerated holes and electrons. The improved photocatalytic activity was characterized with both UVA and visible light irradiation using an in-house built gas-phase photoreactor., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)