Photocatalysis offers a sustainable solution for essential reactions such as CO₂ conversion and water splitting, but constraints in catalyst properties like bandgap and active site availability often limit its efficiency. High-entropy oxides (HEOs), which incorporate five or more different cations, present significant potential for this application due to their elemental diversity. This study explores active HEO development for photocatalytic applications by integrating cations with d⁰ and d¹⁰ electronic configurations. A single-phase HEO with a monoclinic structure was successfully synthesized, comprising elements with d⁰ (titanium, zirconium, niobium and tantalum) and d¹⁰ (zinc) electronic configurations. Comprehensive analyses of its microstructure, chemical composition, optical properties and photocatalytic activity were conducted. The resulting TiZrNbTaZnO₁₀ exhibited superior UV and visible light absorption, a low bandgap of 2.5 eV, minimal radiative electron-hole recombination and high stability under photocatalytic conditions. Remarkably, TiZrNbTaZnO₁₀ outperformed the TiZrHfNbTaO₁₁ photocatalyst which contains solely d⁰ electronic configuration. This enhanced performance is attributed to the mixed electronic configurations fostering heterogeneous chemical environments, which facilitate efficient charge carrier separation and transfer.

The hydride phase of Ti₅₀V₂₀Cr₃₀ alloy cast with 4 wt% of 7Zr+10Ni has been investigated. Pressure composition desorption isotherms were measured at 150 °C and 200 °C. These isotherms revealed same desorption of 1.5 wt% at 150 °C and 200 °C. The evolution of the crystal structure upon dehydrogenation was investigated by in-situ neutron diffraction. A sample was fully deuterated at room temperature under 2000 kPa pressure. Afterwards, the sample was heated from 120 °C to 266 °C under vacuum and neutron diffraction patterns were recorded as a function of temperature. It was found that the alloy started to desorb very quickly at 200 °C. The amount of fcc phase was monitored using the relative intensity of the fcc phase compared to a standard. At 266 °C only 10% hydride phase was seen, which was confirmed by X-ray diffraction. Besides the fcc phase, a minor aluminum phase due to the heating element was also observed in all patterns. Thermal expansion coefficient of Al and fcc phase were calculated. Using the aluminum peaks as reference, it was found that deuterium occupancy reflect the phase abundance of the fcc deuteride.

Magnesium hydride has been studied extensively for applications as a hydrogen storage material owing to the favourable cost and high gravimetric and volumetric hydrogen densities. However, its high enthalpy of decomposition necessitates high working temperatures for hydrogen desorption while the slow rates for some processes such as hydrogen diffusion through the bulk create challenges for large-scale implementation. The present paper reviews fundamentals of the Mg–H system and looks at the recent advances in the optimisation of magnesium hydride as a hydrogen storage material through the use of catalytic additives, incorporation of defects and an understanding of the rate-limiting processes during absorption and desorption.