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For the purpose of hydrogen production with free solar energy, the photoelectrochemical (PEC) water-splitting process grabbed attention as a sustainable route. PEC systems offer several benefits to produce hydrogen, including low environmental impact. For the PEC water oxidation process, Bi2O3 (BO) is considered a very promising semiconductor due to its moderate bandgap of 2.65 eV and can exist in various phases. In order to determine the optimum growth temperature of Bi2O3 for the PEC water splitting reaction and the photocatalytic dye degradation reaction, a series of bismuth (III) oxide semiconductors (SC) is developed in the present work using bismuth nitrate as a precursor varying the annealing temperatures (200–800 °C) in air. The optimized Bi2O3 exhibits the highest photo-activity for the degradation of Rhodamine B target pollutants, which was confirmed by different physicochemical and photocatalytic experimental studies. The sample annealed at an optimized temperature of 650 °C achieved the maximum photocurrent of 0.19 mA cm−2 for water splitting reaction in the presence of phosphate buffer solution with 0.1 M Na2SO4 (pH 7), under periodic chopped illumination of UV–vis light with 100 mW cm−2 light intensity at 1.17 V versus Ag/AgCl. The n-type nature of the semiconductor has been determined through Mott-Schottky analysis. Bi2O3 facilitates the photo-activated electron–hole charge separation and migration due to its relative band position, and as a result, the stable performance of the semiconductor was also reported. The degradation reaction in the presence of scavenger materials such as triethanolamine (TEOA), tertiary butyl alcohol (TBA) and p-benzoquinone (BQ) has also been studied to propose the most plausible mechanism of degradation reaction. [ABSTRACT FROM AUTHOR]

The improvement of the water oxidation capability of bismuth molybdate (BM) with selective metal addition under illumination was examined. BM and its Zn-modified (different atomic %) photoanodes were developed over conducting glass substrate through the cost-effective drop-cast method. The maximum photocurrent of ~ 240 µA/cm2 at an applied potential of 1.3 V vs Ag/AgCl was recorded for the 2% Zn modified sample in 0.1 M Na2SO4 solution (PBS, pH 7) under 100 mW/cm2 illuminations. Surface characterizations like scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, and optical analysis such as UV–vis absorbance, photoluminescence, FT-IR, and Raman spectroscopic analyses were performed to determine the physicochemical properties of the semiconductor. The pure bismuth molybdate shows an optical band gap of ~ 2.78 eV, which decreases for the Zn-modified sample, and a minimum of 2.55 eV is detected for the optimized sample. The XRD analysis also reveals that Zn addition into the bismuth molybdate matrix decreases crystallite size with variation in proportions of the constituent metal oxides. The stability of the semiconductors regarding the PEC water oxidation reaction indicates promising results even under continuous illumination for 1 h. The Mott-Schottky study reveals the n-type nature of the semiconductors, whereas the Nyquist analysis indicates minimum charge transfer resistance for the 2% Zn-BMO sample. The PEC action spectra for the optimized photoanode indicate a maximum of 34% incident photon to current conversion efficiency with corresponding 38% absorbed photon to current conversion efficiency, which is more than three times than that of the pure bismuth molybdate. [ABSTRACT FROM AUTHOR]

In this paper, graphite‐like carbon nitride‐indium vanadate (g‐C3N4/InVO4) composites have been synthesized via a mixing‐calcination method. Physico‐chemical and photocatalytic experiments suggested that the optimized g‐C3N4/InVO4 composite demonstrates highest photo‐activity in degrading Rhodamine B and para‐nitrophenol as target pollutants. The electrochemical impedance spectroscopic (Mott‐Schottky) analysis confirms n‐type semiconductivity for these materials whereas the composite material exhibited highest 13 μA/cm2 photocurrent under periodic UV‐Visible irradiation for water oxidation. The relative band positions indicate inter‐band interactions between heterojunctions of g‐C3N4 and InVO4 facilitating the separation and migration of photogenerated electron‐hole pairs and a stable performance was reported. [ABSTRACT FROM AUTHOR]