Surface contamination by microbes is a major public health concern. A damp environment is one of potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO₂) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proven as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu)-doped TiO₂ (Cu-TiO₂) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO₂ was carried out via sol-gel technique. Cu-TiO₂ further calcined at various temperatures (in the range of 500–700 °C) to evaluate the thermal stability of TiO₂ anatase phase. The physico-chemical properties of the samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV–visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO₂ was maintained well, up to 650 °C, by the Cu dopant. UV–vis results suggested that the visible light absorption property of Cu-TiO₂ was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasize the introduction of Cu⁺ and Cu²⁺ ions by replacing Ti⁴⁺ ions in the TiO₂ lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9999%) was attained in 30 min of visible light irradiation by Cu-TiO₂.

Graphitic carbon nitride (g-C₃N₄) and titanium dioxide (TiO₂) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C₃N₄ has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO₂ and g-C₃N₄. A simple method of preparing g-C₃N₄ through the pyrolysis of melamine was employed, which was then added to undoped TiO₂ material to form the g-C₃N₄–TiO₂ system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse absorbance, and photoluminescence analysis. Photocatalysis studies were conducted using the model dye, rhodamine 6G utilizing visible and UV light irradiation. Raman spectroscopy confirmed that a composite of the materials was formed as opposed to a mixture of the two. Using XPS analysis, a shift in the nitrogen peak to that indicative of substitutional nitrogen was detected for all doped samples. This is then mirrored in the diffuse absorbance results, which show a clear decrease in band gap values for these samples, showing the effective band gap alteration achieved through this preparation process. When g-C₃N₄–TiO₂ samples were analyzed under visible light irradiation, no significant improvement was observed compared that of pure TiO₂. However, under UV light irradiation conditions, the photocatalytic ability of the doped samples exhibited an increased reactivity when compared to the undoped TiO₂ (0.130 min⁻¹), with 4% g-C₃N₄–TiO₂ (0.187 min⁻¹), showing a 43.9% increase in reactivity. Further doping to 8% g-C₃N₄–TiO₂ lead to a decrease in reactivity against rhodamine 6G. BET analysis determined that the surface area of the 4% and 8% g-C₃N₄–TiO₂ samples were very similar, with values of 29.4 and 28.5 m²/g, respectively, suggesting that the actual surface area is not a contributing factor. This could be due to an overloading of the system with covering of the active sites resulting in a lower reaction rate. XPS analysis showed that surface hydroxyl radicals and oxygen vacancies are not being formed throughout this preparation. Therefore, it can be suggested that the increased photocatalytic reaction rates are due to successful interfacial interactions with the g-C₃N₄-doped TiO₂ systems.

To contribute to solving global energy problems, a multifunctional CoFe₂O₄ spinel was synthesized and used as a catalyst for overall water splitting and as an electrode material for supercapacitors. The ultra-fast one-step electrodeposition of CoFe₂O₄ over conducting substrates provides an economic pathway to high-performance energy devices. Electrodeposited CoFe₂O₄ on Ni-foam showed a low overpotential of 270 mV and a Tafel slope of 31 mV/dec. The results indicated a higher conductivity for electrodeposited compared with dip-coated CoFe₂O₄ with enhanced device performance. Moreover, bending and chronoamperometry studies suggest excellent durability of the catalytic electrode for long-term use. The energy storage behavior of CoFe₂O₄ showed high specific capacitance of 768 F/g at a current density of 0.5 A/g and maintained about 80% retention after 10,000 cycles. These results demonstrate the competitiveness and multifunctional applicability of the CoFe₂O₄ spinel to be used for energy generation and storage devices.

The tackling of carbon deposition during the dry reforming of biogas (BDR) necessitates research of the surface of spent catalysts in an effort to obtain a better understanding of the effect that different carbon allotropes have on the deactivation mechanism and correlation of their formation with catalytic properties. The work presented herein provides a comparative assessment of catalytic stability in relation to carbon deposition and metal particle sintering on un-promoted Ni/Al₂O₃, Ni/ZrO₂ and Ni/SiO₂ catalysts for different reaction temperatures. The spent catalysts were examined using thermogravimetric analysis (TGA), Raman spectroscopy, high angle annular dark field scanning transmission electron microscopy (STEM-HAADF) and X-ray photoelectron spectroscopy (XPS). The results show that the formation and nature of carbonaceous deposits on catalytic surfaces (and thus catalytic stability) depend on the interplay of a number of crucial parameters such as metal support interaction, acidity/basicity characteristics, O^2– lability and active phase particle size. When a catalytic system possesses only some of these beneficial characteristics, then competition with adverse effects may overshadow any potential benefits.