This study is devoted to the preparation of a Ni–Al alloy (32 at.
In this work, MnAl2O4 spinel is introduced for the first time as an efficient visible-light photocatalyst for the degradation of Rhodamine B (RhB). The material was synthesized by a controlled co-precipitation route and extensively examined to unveil its structural, optical, dielectric, and electronic characteristics. MnAl2O4 exhibits a direct optical band gap of 2.05 eV and weak photoluminescence intensity, indicating suppressed electron–hole recombination and enhanced charge-carrier separation. The refractive index, extinction coefficient, dielectric permittivity, relaxation time, and conductivity profiles reveal strong light–matter interaction, defect-mediated transitions, and favorable dielectric stability, all of which contribute to efficient visible-light activation. XPS valence band analysis places the valence band maximum at 1.87 eV, allowing determination of the conduction band minimum at − 0.18 eV, confirming the material’s ability to generate both ⋅O2⁻ and ⋅OH radicals under illumination. Photocatalytic experiments demonstrate that MnAl2O4 achieves 58.5
CuAl₂O₄ spinel oxide was synthesized via a co-precipitation route and evaluated as a non-noble electrocatalyst for the hydrogen evolution reaction (HER) in alkaline media. X-ray diffraction and Raman spectroscopy confirmed the formation of a phase-pure cubic spinel structure, while scanning electron microscopy revealed an agglomerated and porous morphology with rough surface features. Electrochemical measurements conducted in 1.0 M KOH using a three-electrode configuration showed that CuAl₂O₄ exhibits clear HER activity with a low onset potential and stable polarization behavior. Electrochemical impedance spectroscopy indicated reduced charge-transfer resistance, and Tafel analysis revealed a Volmer-dominated reaction mechanism, identifying water dissociation as the rate-determining step. Direct hydrogen evolution measurements demonstrated stable and continuous hydrogen generation with a production rate of approximately 1053.5 μmol h⁻1. These results demonstrate that CuAl₂O₄ is a stable and active aluminate spinel for alkaline hydrogen evolution and highlight its potential as an earth-abundant electrocatalyst. .
The development of efficient and sustainable photocatalysts for hydrogen generation is a key step in addressing the global energy and environmental crises. In this study, spinel ferrite nanoparticles with the general formula MFe2O4 (M = Mn, Ni, Cu) were synthesized via a facile co-precipitation route followed by thermal treatment, and their physicochemical and photocatalytic properties were systematically investigated. Structural analysis by X-ray diffraction confirmed the successful formation of phase-pure spinel ferrites, whereas SEM and EDX revealed distinct morphological features and uniform elemental distributions in the manufactured samples. Raman spectroscopy provided evidence of cation-dependent lattice ordering, and UV–Vis diffuse reflectance measurements showed band gap values of 1.32 eV (MnFe2O4), 1.43 eV (CuFe2O4), and 1.78 eV (NiFe2O4). Photocatalytic H2 evolution experiments under visible-light irradiation demonstrated that MnFe2O4 exhibited a superior capability, reaching nearly 150 μmol of H2 within 25 min, outperforming NiFe2O4 by 1.36 times and CuFe2O4 by 2.14 times. The superior photocatalytic ability of MnFe2O4 can be attributed to its narrower band gap, porous morphology, and enhanced structural order, which synergistically promote visible light absorption, charge segregation, and surface redox reactions. This comparative study highlights the pivotal role of cation substitution in tailoring the electronic and structural properties of spinel ferrites and establishes MnFe2O4 as a highly promising photocatalyst for cost-effective and environmentally friendly hydrogen production.
A NiCoP–graphene hybrid electrode supported on three-dimensional nickel foam (NiCoP–Gr/NF) was successfully fabricated and evaluated for the hydrogen evolution reaction (HER) in alkaline media. The electrode was prepared via a two-step process involving electrophoretic deposition of graphene onto nickel foam followed by phosphidation, enabling uniform incorporation of graphene within the bimetallic NiCoP matrix. Structural and surface characterizations (SEM, EDX, XRD, Raman spectroscopy, and XPS) revealed a homogeneous and porous coating composed of ultrafine NiCoP nanoparticles tightly anchored on wrinkled graphene sheets across the nickel foam framework. Electrochemical testing in 1 M KOH demonstrated an overpotential of 168 mV at a current density of 10 mA cm⁻2 and a Tafel slope of 48.9 mV dec⁻1, indicating fast HER kinetics. The improved catalytic performance is attributed to the synergistic interaction between NiCoP and graphene, which enhances charge-transfer efficiency, increases electrochemically active surface area, and promotes efficient electrolyte diffusion within the three-dimensional porous structure. These results demonstrate the effectiveness of the NiCoP–graphene hybrid architecture as a robust and efficient electrode for alkaline hydrogen evolution.
