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• Z-scheme Au-NPs-WO 3 /TiO 2 composite synthesized for H 2 production under visible light. • Synergistic effect of Au/WO 3 greatly enhanced H 2 evolution via Z-scheme and SPR effect. • H 2 yield 17,200 ppm h−1gcat−1 achieved over composite, a 5.89 folds higher than pure TiO 2. • Photocatalytic water splitting and phenol reforming yielded highest H 2 under visible light. • Highest photostability prevailed for continuous CO 2 and H 2 production over Au-WO 3 /TiO 2. Au-NPs-embedded Z-scheme WO 3 /TiO 2 hetero-junction for boosting photocatalytic H 2 evolution from glycerol-water mixture under visible light has been investigated. The composite samples, synthesized by a sol-gel assisted photo-deposition method, gave higher visible light absorption through Surface Plasmon Resonance (SPR), larger BET surface area and hindered recombination of charge carrier. Highest H 2 evolution rate of 17200 ppm h−1 gcat−1 was obtained over 0.5%Au-loaded WO 3 /TiO 2 which was 4.46 and 5.89 folds higher than WO 3 /TiO 2 and TiO 2 , respectively. This divulges that constructing WO 3 /TiO 2 Z-scheme hetero-junction adjusted redox potential, while decorating plasmonic Au-NPs enables faster charges separation with higher visible-light absorption through SPR, resulting in superior H 2 production. In addition, both water splitting and photocatalytic glycerol reforming contributed towards excellent H 2 formation. The apparent quantum yield of 28.3% (λ ~ 420 nm) was attained and catalyst prevailed photo-stability for H 2 evolution in cyclic runs. This study provides new insight about constructing plasmonic assisted Z-scheme assembly for solar fuels production. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) hierarchical carbon nitrides nanorods (HCNNRs) mediated by cobalt was designed and synthesized using a template free hydrothermal approach for improving solar light assisted H 2 evolution. The performance of 1D HCNNTs was significantly enhanced compared to bulk g-C 3 N 4 due to larger active surface area, more visible light utilization and superior charge carrier along the unidirectional flow pathways. The 2% Co/HCNNRs (1D) exhibited excellent photocatalytic efficiency and optimal H 2 yield reached up to 620 µmol g−1, which is 11.27 and 17.71 folds more than it was attained with pure HCNNR and bulk g-C 3 N 4 , respectively. This reveals that 1D structure helps to accelerate charge transport, whereas, Co works as a mediator to trap electrons, thus improving photocatalytic performance. The crucial operating parameters such as sacrificial reagents, feed concentration and catalyst loading were further optimized based on highest H 2 evolution. Interestingly, mass transfer, charge transfer and amount of photoinduced charges were greatly dependent on the operating parameters. Higher methanol and lower TEOA concentration were beneficial to yield highest photoactivity and stability. This work provides new approach to construct template free 1D nanorods and would be beneficial to enhance performance in other solar energy related applications. [Display omitted] • 1D porous graphic carbon nitride was fabricated using facile hydrothermal approach. • Higher porous structure with faster charge carrier separation was observed in 1D structure. • Using 1D Co/HCNNR, significantly higher H 2 was obtained compared to bulk g-C 3 N 4. • Catalyst loading, feed concentration and sacrificial reagents greatly affect activity and stability. [ABSTRACT FROM AUTHOR]

Graphene-bridged, carbonate-coordinated and lanthanum modified TiO 2 nanocomposite (La/Ti3+/TiO 2 /La 2 O 2 CO 3 /rGO) was established using sol-gel assisted modified hydrothermal method followed by acidic/basic heat treatment. The synergistic effect of La/La 2 O 2 CO 3 in rGO bridged Ti+3/TiO 2 nanocomposite was investigated for dynamic H 2 production from ethylene glycerol-water mixture in a slurry phase continuous flow photoreactor system. La-TiO 2 /rGO showed H 2 evolution rate of 462 μmol/h which was about 1.24, 1.51 and 5.13 folds higher compared to La/TiO 2 , rGO/TiO 2 and pure TiO 2 samples, respectively. Furthermore, when La-TiO 2 /rGO nanocomposite was treated under H 2 /CO 2 atmosphere, a great potential in photocatalytic H 2 production with a rate of 583 μmol/h was obtained, which was ~1.02, 1.17 and 1.26 times higher than using H 2 , CO 2 and N 2 atmospheres, respectively. This significantly enhanced productivity was due to formation of La 2 O 2 CO 3 , increased absorptive properties of TiO 2 and changes in elemental level like Ti3+ state, which improves light absorption properties and producing more electrons with their hindered recombination rate by rGO. Specifically, existence of La 2 O 2 CO 3 could facilitate the basicity of catalyst and contributes in the decomposition of ethylene glycol for H 2 evolution. Next, apparent quantum yield of La-TiO 2 /rGO calcined in CO 2 /H 2 composite was 1.3 folds higher than using La-TiO 2 /rGO composite. Moreover, the stability comparison reveals that CO 2 /H 2 treated sample showed stability in cyclic runs due to better interactions of its components and formation of interface species like Ti3+ and La 2 O 2 CO 3. Therefore, fabrication of composite under well-controlled atmospheric heat treatment could be promising to develop graphene supported metal oxides with their unique structures towards visible light enhanced photocatalytic H 2 production applications. Image 1 • rGO/La doped TiO 2 composite fabricated by treatment in CO 2 /H 2 atmosphere. • La-co-catalyzed rGO-bridged TiO 2 composite yielded H 2 of 5.13 folds higher than TiO 2. • Catalyst heat treatment in CO 2 /H 2 atmosphere yielded 1.26 folds higher H 2 than using N 2. • Formation of Ti3+, La 2 O 2 CO 3 and increased conductivity of rGO improved efficiency of La-TiO 2 /rGO. • Catalyst treated in CO 2 /H 2 gave higher stability in cyclic runs than N 2 atmosphere. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D porous graphic carbon nitride was fabricated using facile hydrothermal approach. • Higher porous structure with faster charge carrier separation was observed in 3D structure. • Using 3D Ni/HCN, significantly higher H 2 was obtained compared to bulk g-C 3 N 4. • Using methanol, much higher H 2 yield was obtained than ethanol, glycerol and TEOA. • Catalyst loading, feed concentration and sacrificial reagents greatly affect activity and stability. Well-designed three-dimensional (3D) nanotextures of graphitic carbon nitride (g-C 3 N 4), synthesized using template free single step method and mediated with nickel as a noble free metal, for solar hydrogen production, has been investigated. The photoactivity was investigated in a slurry type continuous flow photoreactor system by using different influential parameters such as hole scavengers, diffusion effects, time, and mass transfer. Compared to bulk g-C 3 N 4 , H 2 yield was increased with 3D hierarchical carbon nitride (HCN) nanotexture. The H 2 evolution rate was reached to 1310 µmol g−1 h−1 with optimized 2 % Ni loading to 3D HCN. This H 2 evolution rate was 19.8 and 24.9 times higher than it was generated using 3D HCN and g-C 3 N 4 , respectively. The special interlayer opening, more light penetration and suppressed charge carrier recombination were the main contributors for this photoactivity enhancement. Among the different influential parameters, lower viscosity, higher number of protons and less diffusion effects were promising to give significantly higher H 2 production. The stability of nanotextures was entirely dependent on the attached reactants over the nickel reactive sites, which was more promising for Triethanolamine (TEOA) than using methanol. This newly developed low-cost 3D HCN can be promising in solar energy conversion and other energy applications. [ABSTRACT FROM AUTHOR]