Dual metal doping and optimization are considered as vital approaches for enhancing the electrocatalytic features toward oxygen evolution reaction.Herein, a sequence of Fe and V dual metal-doped mesoporous cobalt oxide (FeV/meso-Co) electrocatalysts was successfully synthesized through citric acid-assisted evaporation-induced self-assembly (EISA) method. The textural, morphological, crystallinity, and electrochemical activities of Fe/V-promoted meso-Co (124 m 2 /g) are found strongly associated with dual (Fe and V) metal concentration. Benefiting from the combined effect of FeV-doping, the FeV/meso-Co exhibited an extremely lower overpotential of 280 mV to reach 10 mA/cm 2 for oxygen evolution reaction (OER) in 1M KOH electrolyte, which was the considerably lowest value among the earlier catalysts, and the FeV/meso-Co showed similar features as IrO 2 electrodes. Furthermore, FeV/meso-Co electrodes display highly durable (>30 hours) electrocatalytic performance for OER. This inexpensive approach of producing transition dual metal-doped mesoporous materials offers excellent promise for fabricating efficient catalysts and other electrochemical energy-conversion devices.

Several inorganic perovskites of iodine, bromine, and chlorine halides have emerged as candidates for various optoelectronic devices. Highquality CsPb(I 1−x Br x ) 3 and CsPb(Br 1−x Cl x ) 3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) inorganic perovskite thin films were prepared in this study using a thermal evaporation system. Experiments and first-principles calculations were conducted to elucidate the structural, electronic, and optical properties of the prepared films at room temperature. The thin-film perovskite band gap was tuned from 1.85 to 3.13 eV by replacing I − with Br − and then Cl − . Dominant excitonic effects on the onset of optical absorption led us to explicitly account for enhancing absorption through the Sommerfield factor, enabling us to extract the electronic band gap and the exciton binding energy correctly. We correlated our experimental results with the theory of first principles and gained insight into the lattice parameters, electronic structure, excitonic binding energy (E b ), dielectric constant (ε), and reduced effective mass (μ) of the carriers. With increasing concentration (x) of Br and Cl, the E b increased from 39.44 meV for pure CsPbI 3 to 63.04 and 96.73 meV for pure CsPbBr 3 and CsPbCl 3 , respectively, because of a decrease in the dielectric constant and the almost constant value of μ at ∼0.051 m e . The Urbach energy (E U ) was calculated and found to fluctuate between 28 and 77 meV.

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Hybrids of low-symmetry (disordered) mesoporous titanium dioxide modified with different weight ratios of cobalt oxide nanoparticles (Co3O4(x)/lsm-TiO2) are prepared using a one-pot self-assembly surfactant template. The physicochemical characterization of Co3O4(x)/lsm-TiO2 hybrids by scanning and transmission electron microscopy, X-ray diffraction, N2 adsorption–desorption isotherms, and X-ray photoelectron spectroscopy confirm the successful incorporation of cobalt oxide nanoparticles (2–3 nm in diameter) with preservation of the highly mesoporous structure of titanium dioxide substrate. Among these mesoporous hybrids, the ~3.0 wt.% Co3O4/lsm-TiO2 exhibits the best performance toward both the oxygen evolution (OER) and reduction (ORR) reactions in alkaline solution. For the OER, the hybrid shows oxidation overpotential of 348 mV at 10 mA cm−2, a turnover frequency (TOF) of 0.034 s−1, a Tafel slope of 54 mV dec−1, and mass activity of 42.0 A g−1 at 370 mV. While for ORR, an onset potential of 0.84 V vs. RHE and OER/ORR overpotential gap (ΔE) of 0.92 V are achieved which is significantly lower than that of commercial Pt/C, hexagonal mesoporous, and bulk titanium dioxide analogous. The Co3O4/lsm-TiO2 hybrid demonstrates significantly higher long-term durability than IrO2. Apparently, such catalytic activity performance originates from the synergetic effect between Co3O4 and TiO2 substrate, in addition to higher charge carrier density and the presence of disordered mesopores which provide short ions diffusion path during the electrocatalytic process.

Visible-light-driven photoelectrochemical (PEC) and photocatalytic water splitting systems featuring heterogeneous semiconductor photocatalysts (oxynitrides, oxysulfides, organophotocatalysts) signify an environmentally friendly and promising approach for the manufacturing of renewable hydrogen fuel. Semiconducting electrode materials as the main constituents in the PEC water splitting system have substantial effects on the device’s solar-to-hydrogen (STH) conversion efficiency. Given the complication of the photocatalysis and photoelectrolysis methods, it is indispensable to include the different electrocatalytic materials for advancing visible-light-driven water splitting, considered a difficult challenge. Heterogeneous semiconductor-based materials with narrower bandgaps (2.5 to 1.9 eV), equivalent to the theoretical STH efficiencies ranging from 9.3% to 20.9%, are recognized as new types of photoabsorbents to engage as photoelectrodes for PEC water oxidation and have fascinated much consideration. Herein, we spotlight mainly on heterogenous semiconductor-based photoanode materials for PEC water splitting. Different heterogeneous photocatalysts based materials are emphasized in different groups, such as oxynitrides, oxysulfides, and organic solids. Lastly, the design approach and future developments regarding heterogeneous photocatalysts oxide electrodes for PEC applications and photocatalytic applications are also discussed.