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Herein, we report the preparation, characterization and investigation of previously unexplored W incorporated iron vanadate (FeVO4) electrodes for solar light driven water oxidation in photoelectrochemical cell. The W incorporated FeVO4 films on F-doped SnO2 substrates have been prepared by layer-by-layer deposition of metal–organic precursor and subsequent thermal decomposition at 550 °C in air. The synthesized films with a band gap of about 2.06 eV are responsive to visible light up to wavelength of ∼600 nm, i.e. being able to harvest ∼45% of the solar spectrum. The W incorporated FeVO4 photoanodes are active materials for photoelectrochemical water oxidation and, yield a significantly enhanced (2.5 fold higher) photocurrent in comparison to pristine FeVO4 photoanodes. This improvement can be attributed to increased n-type conductivity by W6+ ion doping in the FeVO4 lattice. The incident photon to current conversion efficiency achieved with developed photoanodes is as high as 6.5% at 400 nm.

Hierarchical architectures consisting of one-dimensional (1D) nanostructures are of great interest for potential use in energy and environmental applications in recent years. In this work, hierarchical tungsten oxide (WO3) has been synthesized via a straightforward, template-free, hydrothermal route from ammonium metatungstate hydrate and implemented in photoanode fabrication for solar water oxidation in photoelectrochemical cells and photocatalytic oxidation of organic pollutant. The flower-like WO3 micro-patterns are constructed by self-organized nanoscale length 1D building blocks, which are single-crystalline in nature, grown along (001) direction and confirm an orthorhombic crystal phase. Time-dependent experiments have been conducted to demonstrate their morphology evolution. The hierarchical architecture based photoanodes produce higher photocurrent (2-fold high) than the nanoparticles based photoanodes from solar water oxidation. The photon to current conversion efficiency achieved with the hierarchical architectures is 45% at 400 nm. The enhanced activity can be attributed to improved charge-separation by superior charge transportation through single-crystalline 1D building blocks.

The hierarchical nanostructures of CdIn2S4 were selectively prepared through hydrothermal process in the presence of different surfactants. Structural study demonstrated existence of cubic spinel structure and micro structural study shown a pretty marigold flower like morphology without any surfactant. The effect of surfactants on the morphology and microstructure of CdIn2S4 has been studied by using Polyvinyl pyrrolidone (PVP) and Cetyltrimethyl ammonium bromide (CTAB) as a surfactants. The CdIn2S4 bipyramids with length of 0.7–1 μm have been obtained using PVP. Interestingly, the nanopetals (thin and transparent) of CdIn2S4 are self assembled into hollow spheres in the presence of CTAB. Considering the importance of these unique nanostructures, the growth mechanism has also been proposed. The optical properties demonstrated the band gap in the range of 2.12–2.29 eV which is well within the visible region. In this contest, photocatalytic activity for hydrogen production using the above nanostructures under visible light was also demonstrated. The prima-fascia observations shows that the bipyramidal CdIn2S4 exhibit excellent photocatalytic activity for hydrogen production (3238 μmolh−1) than other nanostructures. Being a nanostructured semiconductor chalcogenide with a good stability will also have potential applications in solar cells and LED.

This article reports our investigation on H2 generation from visible light (λ ≥ 420 nm) photodecomposition of H2S by nanomaterial catalysts, α-Fe2O3 and its chemically modified Fe2−xGaxO3 (Ga substitution at x = 0.6, FeGaO3-I and x = 1.0, FeGaO3-II). Simple template-free hydrothermal technique was employed to synthesize the three photocatalysts. XRD study reveals rhombohedral nanocrystalline structure and FESEM shows nanospheres morphology for Fe2O3 and nanosticks/nanorods for both FeGaO3-I, and FeGaO3-II. In H2 generation, Fe2O3 and FeGaO3-II perform moderate and almost same activities in the fresh and used conditions (quantum yield, QY = 6.0–6.8% at 550 nm). Contrarily, fresh FeGaO3-I exhibits a greater activity (11.2% QY) and the activity is further enhanced (QY = 15.3%) on regeneration and reuse. The intricacy, as resolved by XRD and FESEM, appears to take place through morphology transformation. The present work, thus, successfully demonstrates H2 generation from H2S by nanostructured photocatalysts involving morphology dependent activity enhancement.

We report here the novel approach to synthesis of layer perovskite photocatalysts, Pb2Ga2Nb2O10 and RbPb2Nb2O7 using solid state route (SSR) and molten salt synthesis (MSS) method. The reported modified MSS method has advantage over conventional SSR method for uniform particle size, well-defined crystal structure, controlled morphology and stoichiometry vis-a-vis photocatalysis. The structural study was performed using X-ray difractometry (XRD) and computation based on density functional theory (DFT). The simulation study showed that both the compounds belong to the Ruddlesden-Popper phase (A′2An−1BnO3n+1; n = 2 or 3). The surface morphology of the materials was studied using field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). The average particles size of perovskites Pb2Ga2Nb2O10 and RbPb2Nb2O7 was in the range 20–40 and 70–90 nm respectively. The efficacy of these materials was studied to particle size and morphology as a visible light driven photocatalyst for the hydrogen generation from H2S. Electronic band structure with DOS has also been performed for both the materials. Being a stable single-phase ternary-layered oxide perovskites and band gap (2.75 eV) in visible domain, they may have potential applications in electronic devices as well.

Photocatalytic application of the thermal catalyst Fe 2 O 3 in hydrogen production from H 2 S requires a chemical modification to lessen/avoid the chemical attack by H 2 S. Incorporating this objective, in the present work FeGaO 3 with equimolar Fe and Ga contents was prepared by solid state (SS) and hydrothermal (HT) routes. The resulting materials, FeGaO 3 -SS and FeGaO 3 -HT are found to have characteristically different crystalline structures and morphology. Their photocatalytic activities in the unloaded/pristine and 1 wt% NiO x -loaded forms as well as in the fresh and used conditions in hydrogen production from H 2 S under visible light ( λ ≥ 420 nm) reveal that the synthesized photocatalysts are stable in their functionalities and the trends are quite interesting and unusual. The structure–activity investigation clearly suggests the key role of their material configurations in deciding photofunctionalities. The fair quantum yields (7–9% at 550 nm), the regenerative and reusable features plus the scope for improvement through optimum Ga content, all make the new photocatalysts promising.

Spinel metal oxide photocatalysts, a rarely studied group in visible light driven photocatalytic decomposition of H 2 S and solar H 2 production, have been investigated in the present work. d 10 p-block element, Ga containing spinel CuGa 2 O 4 in pristine and Fe 3 + doped ( CuGa 2 - x Fe x O 4 , x = 0.6 ) states, was prepared by ceramic route without/with noble metal oxide, NiO / RuO 2 loading to the extent of 1 wt%. XRD analysis reveals a single-phase cubic spinel crystalline structure for all the catalysts. FESEM displays an irregular-shaped grain morphology for CuGa 2 O 4 and smaller size almost cubic particles for CuGa 2 - x Fe x O 4 . Energy dispersive X-ray spectroscopy suggests a chemical composition consistent with the stoichiometric molecular formula. Optically, the catalysts display an intensive light absorption in UV and visible regions with an onset at about 900 nm in the near IR region. Fe 3 + doping constructively influences the morphology and optical properties of pristine CuGa 2 O 4 . All these physico-chemical and material characteristics infuse a facile catalytic function into the prepared spinel oxides such that the naked CuGa 2 O 4 and CuGa 2 - x Fe x O 4 spinels exhibit a moderate to fairly good photocatalytic activity while the co-catalyst-loaded CuGa 2 - x Fe x O 4 spinel performs an exceedingly good photocatalytic activity with 15% quantum efficiency. Thus, the present work leads to the emergence of functionally high performance, stable and visible active ( λ ⩾ 420 nm ) photocatalysts in the spinel group for the production of solar hydrogen from H 2 S .

Rose-red color Nb 2 Zr 6 O 17 - x N x oxynitride photocatalyst was synthesized by thermal ammonolysis of Nb 2 Zr 6 O 17 at 1073 K. TEM image of Nb 2 Zr 6 O 17 - x N x sample showed prismatic pseudo orthorhombic shaped particles with clear edges and an average particle size in the range of 80–90 nm. The photocatalytic activities of the oxynitride samples were studied for hydrogen production by H 2 S splitting under visible light irradiation. The oxynitride Nb 2 Zr 6 O 17 - x N x gave the quantum yield of 13.5% in the production of hydrogen from decomposition of hydrogen sulfide under visible light irradiation.