Photo-sensing properties of Cd-doped In2S3 thin films fabricated via low-cost nebulizer spray pyrolysis technique

In this study, we report the fabrication of cadmium-doped indium sulfide thin films (In₂S₃:Cd) using a low-cost nebulizer-aided spray pyrolysis process at 350 °C on glass substrates for photo-sensing applications. The impact of 0, 2, 4, and 8 wt% cadmium concentrations on the structure, morphology, optical properties, and photo-sensing capabilities of In₂S₃ thin films were examined systematically. From X-ray diffraction (XRD) analysis, the major peak is located in the (103) plane for all Cd-doped In₂S₃ thin film samples, and the maximum crystallite size for the 4 wt% sample is 59 nm. The field emission scanning electron microscope (FESEM) image revealed a homogenous large-grained surface of Cd-doped In₂S₃ film that completely covered the substrate. UV–Vis absorption analysis demonstrated good absorption for all thin film samples in the visible and ultraviolet regions of the electromagnetic spectrum, particularly, the 4% Cd-doped concentration showed excellent absorption as is observed from Tauc relation. The highest PL intensity at 680 nm was observed for the sample coated with 4 wt% of Cd. Under UV light, the I–V behavior depicts a light current of 1.06?×?10^–6 A for a 5 V bias voltage. The In₂S₃: Cd (4%) sample had the highest responsivity of 2.12?×?10^?1A/W and a detectivity of 1.84?×?10¹¹ Jones, with a high EQE of 50%. The study manifests that the developed Cd (4%)-doped In₂S₃ thin film sample might be better suited for the application of photodetectors.

     

Activation effect of silver nanoparticles on the photoelectrochemical performance of mesoporous TiO2 nanospheres photoanodes for water oxidation reaction

This work reports the photodeposition of Ag nanoparticles onto mesoporous TiO₂ (m-TiO₂) pre-formed by the evaporation-induced self-assembly method. Photoanodes of Ag/m-TiO₂ assembled by electrophoretic disclose a superior photoelectrochemical (PEC) performance for water oxidation reaction related to m-TiO₂. The photoanodes physicochemical investigations witness the even arrangement of m-TiO₂ nanospheres particles over the substrates. The PEC study displays a steady photocurrent density of 1 mAcm^?2 at ?1.0 V vs SCE was attained for Ag/m-TiO₂ photoanodes in visible light illumination and it is nearly twofold enhancements in comparison with m-TiO₂ photoanodes. The observed superior PEC nature was attributed to the reduced band-gap energy and charge recombination that caused from the incorporation of plasmonic photodeposited Ag nanoparticles on m-TiO₂ nanospheres photoanodes.     

Growth of iron diselenide nanorods on graphene oxide nanosheets as advanced electrocatalyst for hydrogen evolution reaction

Advanced electrocatalysts for the fabrication of sustainable hydrogen from water splitting are innermost to energy research. Herein, we report the growth of iron diselenide (FeSe₂) nanorods on graphene oxide (GO) sheets using two-step process viz., simple hydrothermal reduction and followed by wet chemical process. The orthorhombic phase of FeSe₂ incorporated GO nanosheet was developed as a low-cost and efficient electrocatalyst for hydrogen evolution reaction (HER) by water splitting. The phase purity, crystalline structure, surface morphology and elemental composition of the synthesized samples have been investigated by UV–visible absorption spectroscopy (UV–vis), fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDS). Voltammetry and Tafel polarization methods have been utilized to assess the performance of various weight ratio of GO nanosheet in FeSe₂ nanorods towards H₂ evolution. Detailed electrochemical investigations revealed that the 30% FeSe₂/GO composite showed a tremendous electrocatalytic HER activity in acidic medium with high cathodic current density of 9.68 mA/cm² at η = 250 mV overpotential and with a Tafel slope of 64 mV/dec. The 30% FeSe₂/GO composite offers a high synergistic effect towards HER activity, which is mainly due to high electrochemical active catalytic sites, low charge-transfer resistance and enhanced electrocatalytic performances of H₂ production. The present analysis revealed the possible application of FeSe₂/GO composite as a promising low-cost alternative to platinum based electrocatalysts for H₂ production.     

Unprecedented solar water splitting of dendritic nanostructured Bi2O3 films by combined oxygen vacancy formation and Na2MoO4 doping

We demonstrate the synergetic effect of Na₂MoO₄-doping and vacuum-annealing on dendritic nanostructured bismuth oxide (Bi₂O₃) thin films prepared by electrodeposition for visible-light-assisted photoelectrochemical (PEC) water oxidation. After evaluating various extents of Na₂MoO₄-doping as well as vacuum-annealing temperatures, it was evidenced that both Na₂MoO₄-doping and vacuum-annealing significantly improved the efficiency and PEC water oxidation performance. Compared to the undoped Bi₂O₃ photoanode, the optimized Na₂MoO₄-doped Bi₂O₃, after vacuum-annealing, resulted in more than 25-fold enhancement in the photoanodic current density to 1.06 mA/cm² at 1.23 V_RHE under AM1.5 G illumination. The PEC enhancement is credited mainly to the increased PEC surface active sites in the Na₂MoO₄-doped vacuum annealed sample. Confirmed by combined XPS and Mott-Schottky (M ? S) analysis, vacuum annealing resulted in surface oxygen vacancies that can contribute to the photocatalytic activity. Besides, Na₂MoO₄-doping resulted in reduced dimensions of the dendritic structure, revealed by FE-SEM and XRD measurements, resulting in larger surface area and, therefore, larger surface/electrolyte contact. This dual strategy (metal doping + vacuum annealing) can be generalized to assemble photoanodes of other materials used for the production of solar fuels. Our results make a valuable step towards efficient Bi₂O₃/BiVO₄ pn heterojunctions.     

A sensitive electrochemical detection of hydroquinone using newly synthesized α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-graphene oxide nanocomposite as an electrode material

This article presents the effect of hematite phase iron oxide (α-Fe₂O₃) on the electrocatalytic activity of graphene oxide (GO) for electrochemical detection of hydroquinone in aqueous solution. The different weight percentage (wt%) (1, 2 and 3%) of α-Fe₂O₃ added GO nanocomposites were synthesized by wet-impregnation method. The cyclic voltammetry studies using 2% α-Fe₂O₃-GO modified glassy carbon electrodes was found to exhibit an excellent electrocatalytic activity than α-Fe₂O₃ and GO electrodes that may be due to the synergistic effect of α-Fe₂O₃nanoparicles and GO sheet. In addition, the modified electrode exhibited a good reproducibility as well as long-term stability. Hence, the 2% α-Fe₂O₃-GO can be a promising catalytic material for electrochemical sensor applications.