G-C₃N₄ with structural defects and low polymerization synthesized by urea as the precursor for photocatalytic H₂ production under visible light.

Perovskite-type oxides lanthanum ferrite (LaFeO₃) photocatalysts were successfully prepared by a facile and cost-effective sol-gel method using La(NO)₃ and Fe(NO)₃ as metal ion precursors and citric acid as a complexing agent at different calcination temperatures. The properties of the resulting LaFeO₃ samples were characterized by powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (IR), transmission electron microscopy (TEM), N₂ adsorption/desorption and photoelectrochemical tests. The photoactivity of the LaFeO₃ samples was tested by monitoring the photocatalytic degradation of Rhodamine B (RhB) and 4-chlorophenol (4-CP) under visible light irradiation, the highest photocatalytic activity was found for LaFeO₃ calcined at 700 °C, which attributed to the relatively highest surface area (10.6 m²/g). In addition, it was found from trapping experiments that the reactive species for degradation were superoxide radical ions (O₂⁻) and holes (h⁺). Photocurrent measurements and electrochemical impedance spectroscopy (EIS) proved the higher photo-induced charge carrier transfer and separation efficiency of the LaFeO₃ sample calcined at 700 °C compared to that that calcined at 900 °C. Band positions of LaFeO₃ were estimated using the Mott-Schottky plots, which showed that H₂ evolution was not likely.

The synthesized ZrO₂/g-C₃N₄ composites exhibit superior performance in water splitting for hydrogen production due to the effective electron–hole separation at the composite interface.

Nanosized SrSnO₃ photocatalysts have been successfully synthesized by microwave synthesis in various ionic liquids (ILs) followed by a heat treatment process to optimize the materials’ crystallinity. The influence of the ILs with various cations such as 1-butyl-3-methylimidazolium ([C₄mim]⁺), 6-bis(3-methylimidazolium-1-yl)hexane ([C₆(mim)₂]²⁺), butylpyridinium ([C₄Py]⁺), and tetradecyltrihexylphosphonium ([P₆₆₆₁₄]⁺) and bis(trifluoromethanesulfonyl)amide ([Tf₂N]⁻) as the anion on the structure, crystallization, and morphology of the products was investigated. The samples were characterized by X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), surface area analysis by gas adsorption, X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–vis spectroscopy, and Raman and IR spectroscopy. According to structure characterization by XRD and Raman spectroscopy all samples crystallized phase-pure in the orthorhombic GdFeO₃ perovskite structure type. SEM reveals that, on the basis of the IL, the obtained SrSnO₃ nanoparticles exhibit different morphologies and sizes. Rod-shaped particles are formed in [C₄mim][Tf₂N], [C₆(mim)₂][Tf₂N]₂, and [P₆₆₆₁₄][Tf₂N]. However, the particle dimensions and size distribution vary depending on the IL and range from quite thin and long needlelike particles with a narrow size distribution obtained in [P₆₆₆₁₄][Tf₂N] to relatively larger particles with a broader size distribution obtained in [C₆(mim)₂][Tf₂N]₂. In contrast, in [C₄Py][Tf₂N] nanospheres with a diameter of about 50 nm form. For these particles the highest photocatalytic activity was observed. Our investigations indicate that the improved photocatalytic activity of this material results from the synergistic effect of the relatively large surface area associated with nanosize and an appropriate energy band structure.

Fuel cell driven cars belong to the ‘zero emission’ vehicles and should contribute to lower CO₂ emissions. However, they contain platinum, which is known as a critical material in the European Union. This study investigated the potential contribution of recycling fuel cell vehicles (FCV) to satisfy the platinum demand arising from a widespread deployment of fuel cell vehicles in Europe. Based on a qualitative examination of the four consecutive steps in the recycling chain (collection, dismantling, disassembly and pre-processing, material recovery) of fuel cell vehicles, two recycling scenarios were developed. Using dynamic material flow analysis, these two recycling scenarios were applied to two scenarios for the market penetration of fuel cell vehicles in nine European lead markets to deliver both the associated impact on platinum demand and the contribution of recycling for meeting this demand. The diffusion of FCV in Europe will not cause a depletion of platinum resources in the short term, as the calculated 537.06 t and 459.24 t in cumulative platinum requirements are far below the currently estimated global reserves. However, concerns regarding the future development of platinum supply and demand remain.

Hexagonal perovskite YFeO₃ was synthesized by a complex-assisted sol-gel technique allowing crystallization at calcination temperatures below 700 °C. As determined by diffuse reflectance spectroscopy (DRS) and Tauc plots, the hexagonal YFeO₃ exhibits a lower optical band gap (1.81 eV) than the orthorhombic structure (about 2.1 eV or even higher) being typically obtained at elevated temperatures (>700 °C), and thus enables higher visible light photocatalysis activity. Structure and morphology of the synthesized YFeO₃ perovskites were analyzed by powder X-ray diffraction (XRD) and nitrogen adsorption, proving that significantly smaller crystallite sizes and higher surface areas are obtained for YFeO₃ with a hexagonal phase. The photocatalytic activity of the different YFeO₃ phases was deduced via the degradation of the model pollutants methyl orange and 4-chlorophenol. Experiments under illumination with light of different wavelengths, in the presence of different trapping elements, as well as photoelectrochemical tests allow conclusions regarding band positions of YFeO₃ and the photocatalytic degradation mechanism. X-ray photoelectron spectroscopy indicates that a very thin layer of Y₂O₃ might support the photocatalysis by improving the separation of photogenerated charge carriers.