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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.

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.

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The asymmetric photocurrent in opposite directions and the rectifying behaviour of all the CuO/PbTiO3 samples reveal the formation of a p–n junction between them, this helps to augment the charge anti-recombination process at the interface and enhance the photocatalytic performance.

A series of visible light responsive nanorods of InGaZn mixed oxide photocatalyst are designed by varying the concentration of In(NO(3))(3)via a solid state reaction method without the need for a surfactant or template. The photocatalysts are characterized by XRD, diffuse reflectance UV-vis spectra, TEM, BET surface area analysis, PL, and photoelectrochemical measurement. Increasing the concentration of In(NO(3))(3) changes the morphology from agglomerated to nanorod-shaped, and reduces surface defects which inhibits the recombination of charge carriers. From photocurrent measurements, the conduction band minimum and valance band maximum of InGaZn (3 : 1 : 1) are found to be -0.75 and 1.65 V at pH 5.9, respectively, which is suitable for oxidation and reduction processes. The photocatalysts are tested towards hydrogen generation under visible light irradiation. Among all the photocatalysts, InGaZn (3 : 1 : 1) gives the best result towards the production of hydrogen energy under visible light irradiation.

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