A highly active nano black TiO ₂ photocatalyst with Pt as a co-catalyst for visible light-assisted hydrogen production from methanol–water is prepared by controlled magnesiothermic treatment in a H ₂ /Ar atmosphere.

Here, we present oxygen-deficient black ZrO_2−x as a new material for sunlight absorption with a low band gap around ~1.5 eV, via a controlled magnesiothermic reduction in 5% H₂/Ar from white ZrO₂, a wide bandgap(~5 eV) semiconductor, usually not considered for solar light absorption. It shows for the first time a dramatic increase in solar light absorbance and significant activity for solar light-induced H₂ production from methanol-water with excellent stability up to 30 days while white ZrO₂ fails. Generation of large amounts of oxygen vacancies or surface defects clearly visualized by the HR-TEM and HR-SEM images is the main reason for the drastic alteration of the optical properties through the formation of new energy states near valence band and conduction band towards Fermi level in black ZrO_2−x as indicated by XPS and DFT calculations of black ZrO_2−x. Current reduction method using Mg and H₂ is mild, but highly efficient to produce solar light-assisted photocatalytically active black ZrO_2−x.

Cubic ordered mesoporous carbon co-doped with N and P shows a high specific capacitance of 210 F g⁻¹ at 1.0 A g⁻¹ and excellent retention of specific capacitance with more than 90% of initial capacitance at a high current density of 10 A g⁻¹ and also for 3000 charge–discharge cycles.

With increasing demand for clean energy and approaching commercialization of polymer electrolyte membrane fuel cells (PEMFCs), replacing expensive Pt-based cathode catalysts with much cheaper non-precious metal (NPM) catalysts has become absolutely essential. This review highlights the parameters that have been considered vital to improving the overall performance of the NPM-based catalysts for oxygen reduction reaction (ORR). In the present review, we focus on well-known catalytic systems in three categories of NPM catalysts, i.e. biomimetic heme–copper oxidase enzymes, non-pyrolyzed/polymeric systems, and pyrolyzed NPM–nitrogen-doped carbon (M–N/C) (M = Fe, Ni, Co, etc.) catalysts. The ORR mechanism on the reported active sites and the effect of varying their local environments are considered and discussed in detail. Among all the catalysts, only pyrolyzed M–N/C catalysts have shown activity and stability much closer to that of the state-of-the-art commercial carbon-supported platinum (Pt/C) catalyst. Although great heights have been climbed in pyrolyzed M–N/C-based catalysts, still general consensuses need to be established regarding the active sites in the NMP-based M–N/C catalysts to help enhance the activity and stability of the catalytic system. By comparing the ORR mechanisms of the three studied systems, various similarities between the active sites are identified and reported comprehensively. On the basis of the information amassed, some future directions for improving the activity, selectivity, and durability of the NPM-based catalysts are also discussed.