A highly active graphitic C 3 N 4 photocatalyst prepared from a mixture of urea and melamine with advanced structural, optical and electronic properties and enhanced photocatalytic activity for the production of hydrogen gas is explored. The prepared photocatalyst is able to generate a high rate of hydrogen gas production (135 mmol h À1 ) by loading with 1 wt% Pt as a co-catalyst. The good separation of C 3 N 4 sheets, lower recombination rate of excitons and the high amount of generated photocurrent have significantly contributed towards the photocatalytic activity of graphitic carbon nitride prepared from a mixture of urea and melamine.C 3 N 4 -M and C 3 N 4 -MU, stability test of C 3 N 4 -MU photoelectrode, mechanism of photocurrent generation over n-type g-C 3 N 4 photoelectrode, characterisation techniques i.e. XRD, optical absorbance spectra, FT-IR spectra and photocatalytic activity for hydrogen production of graphitic C 3 N 4 prepared by taking melamine and urea with molar ratios of 1 : 2 and 2 : 1. See

Noble‐metal Au nanoparticles deposited on graphitic carbon nitride polymer (g‐C3N4) photocatalyst by a facile deposition–precipitation method exhibited high photocatalytic activity for hydrogen gas production under visible‐light irradiation. The Au/g‐C3N4 nanocomposite plasmonic photocatalysts were characterized by X‐ray diffraction spectroscopy, diffuse reflectance UV/Vis spectroscopy, FTIR spectroscopy, field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, selected‐area electron diffraction, X‐ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical measurements. We studied the effect of Au deposition on the photocatalytic activity of g‐C3N4 by investigation of optical, electronic, and electrical properties. Enhanced photocatalytic activity of Au/g‐C3N4 naocomposite for hydrogen production was attributed to the synergic mechanism operating between the conduction band minimum of g‐C3N4 and the plasmonic band of Au nanoparticles including high optical absorption, uniform distribution, and nanoscale particle size of gold. The mechanism of te photocatalytic activity of the nanocomposite photocatalyst is discussed in detail. Deposition of Au nanoparticles on g‐C3N4 was optimized and it was found that 1 wt % Au‐loaded g‐C3N4 composite plasmonic photocatalyst generated a photocurrent density of 49 mA cm−2 and produced a hydrogen gas amount of 532 μmol under visible light, which were more than 3000 times higher and 23 times higher, respectively, than the values of neat g‐C3N4.

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With the purpose of efficient electron-hole separation and enhancement of photocatalytic performance in the visible region, we have fabricated a novel p-BiOI/n-ZnTiO3 heterojunction by a precipitation-deposition method and studied its activity toward dye degradation. The physicochemical characteristics of the fabricated BiOI/ZnTiO3 heterojunctions were surveyed by powder X-ray diffraction pattern (PXRD), BET-surface area, diffuse reflectance UV-vis (DRUV-vis), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL spectra), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurement. The photosensitization effect of BiOI enhanced the spectral response of ZnTiO3 from UV to visible region, making all the BiOI/ZnTiO3 heterojunctions active under visible light. The PEC measurement confirmed the p-type character of BiOI and n-type character of ZnTiO3. The optimal amount of BiOI in BiOI/ZnTiO3 heterojunctions was found to be 50% which degraded 82% of 50 ppm Rh 6G under visible light irradiation. The degradation rate of 50% BiOI/ZnTiO3 heterojunction was found to be 9.8 and 11.1 times higher than that of bare BiOI and ZnTiO3, respectively. The photosensitization effect of BiOI and the formed heterojunction between p-type BiOI and n-type ZnTiO3 contribute to improved electron-hole separation and enhancement in photocatalytic activity.

Fast recombination of photoinduced charge carriers is a major problem in the case of semiconductor based photocatalysts, which must be solved for their potential application in photocatalysis. In this work, photostable CdS QDs/BiOI composites have been successfully fabricated by a two-step precipitation–deposition method. The prepared samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflection spectroscopy (UV–vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Mott–Schottky, and electrochemical impedance analysis. The potential applications of CdS QDs/BiOI composite materials have been tested toward decolorization of rhodamine B (RhB) solution and hydrogen generation under solar light and visible light irradiation, respectively. It has been observed that hydroxyl radicals, electrons, and holes played a major role in decolorization of RhB solution. Among all prepared photocatalysts, 4% CdS QDs/BiOI composite was able to decolorize 82% of RhB solution in 1 h and 203 μmol/h of H2 under solar light and visible light irradiation, respectively. The highest activity has been ascribed to optimal loading of CdS QDs, good formation of composites, and the lowest recombination of charge carriers.

Photocatalytic generation of H and O by water splitting remains a great challenge for clean and sustainable energy. Taking into the consideration promising heterojunction photocatalysts, analogous energy issues have been mitigated to a meaningful extent. Herein, we have architectured a highly efficient bifunctional heterojunction material, i.e., p-type Co(OH) platelets with an n-type ZnCr layered double hydroxide (LDH) by an ultrasonication method. Primarily, the Mott-Schottky measurements confirmed the n- and p-type semiconductive properties of LDH and CH material, respectively, with the construction of a p-n heterojunction. The high resolution transmission electron microscopy results suggest that surface modification of ZnCr LDH by Co(OH) hexagonal platelets could form a fabulous p-n interfacial region that significantly decreases the energy barrier for O and H production by effectively separating and transporting photoinduced charge carriers, leading to enhanced photoreactivity. A deep investigation into the mechanism shows that a 30 wt % Co(OH)-modified ZnCr LDH sample liberates maximum H and O production in 2 h, i.e., 1115 and 560 μmol, with apparent conversion efficiencies of H and O evolution of 13.12% and 6.25%, respectively. Remarkable photocatalytic activity with energetic charge pair transfer capability was illustrated by electrochemical impedance spectroscopy, linear sweep voltammetry, and photoluminescence spectra. The present study clearly suggests that low-cost Co(OH) platelets are the most crucial semiconductors to provide a new p-n heterojunction photocatalyst for photocatalytic H and O production on the platform of ZnCr LDH.

This study highlights the recent trends in the structural, textural and morphological variations of g-C3N4 for visible-light-induced hydrogen evolution.

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