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The emerging ultrawide-bandgap AlGaN alloy system holds promise for the development of advanced materials in the next generation of power semiconductor and UV optoelectronic devices. Within this context, heterostructures based on III-nitrides are very popular in view of their applications as electronic and optoelectronic components. AlGaN-based deep UV emitters are gaining visibility due to their disinfection capabilities. Likewise, high electron mobility transistors are attracting increasing attention owing to their superior electron transport which yields high-speed and high-power applications. These devices are conventionally made of AlGaN/GaN heterostructures grown on foreign substrates. However, structural defects, including stress induced by a mismatch in unit cell parameters and the presence of dislocations, can not only decrease the efficiency of the light emitters (by facilitating the non-radiative recombination of electron–hole pairs), but also impede electron mobility within the two-dimensional electron gas at the AlGaN/GaN interface. Therefore, the significance of obtaining high-quality AlGaN layers becomes evident. Including a thin AlN interlayer between the GaN buffer layer and AlGaN is a possible answer to address these drawbacks. Not only do we show that a thin AlN layer, approximately ≤3 nm in thickness, between the GaN buffer and AlGaN layers, is effective in decreasing the dislocation densities in the AlGaN layer by around 30%, but also this is responsible for an increase in the electron mobility (approximately 33%) compared to a classical AlGaN/GaN heterostructure. Additionally, the resulting heterostructure exhibits better optical quality, with a 7-fold increase in intensity as well as a 20% reduction in full-width at half-maximum in the AlGaN emission. [ABSTRACT FROM AUTHOR]

Few-layered binary 2D transition metal chalcogenides have been comprehensively employed in photodetector systems thanks to their intrinsic band gap structure and a high in-plane charge carrier mobility. Their rich chemistry is further broadened when considering ternary 2D chalcogenide materials, giving the possibility to prepare isomorphic materials characterized by various metal distributions within the framework of a crystal structure. Whereas the "inverse" A(τ)B(Ω)(τ)2X4 hexagonal structures (e.g. ZnIn2S4) have been widely studied in photocatalysis, "normal" AII(Ω) BIII(τ)2XVI4 phases have not been considered so far. In this study, a NiGa2S4 photodetector has been prepared by drop-casting the exfoliated crystals onto ITO glass. Their photoresponse has been analyzed either in the absence or in the presence of an electron donor species (EtOH) in the electrolyte solution. Ethanol acts as a fuel in the PEC photodetector system boosting their performance by a factor of ∼x49 in terms of the responsivity at a given wavelength. Moreover, the spectral response is expanded from blue to far IR wavelengths, reaching responsivity values from 48 to 7 mA W−1. The dynamics of photogenerated electrons and holes has been studied using laser flash photolysis. The stability of the "fueled" PEC photodetector has been evaluated through long-term tests which have shown a stable response over extended periods. It is anticipated that the present work can provide fundamental insight into the field of PEC semiconductor-based photodetectors, offering an extendable strategy to engineer high-performance PEC devices. [ABSTRACT FROM AUTHOR]

Electrochemical synthesis of NH3 is a carbon‐free alternative to the traditional Haber–Bosch process. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than from the nitrogen reduction reaction (NRR) due to the difficult cleavage of the inert triple bond of nitrogen gas. Here, a novel heterogeneous catalyst is reported based on iron (Fe) single‐atoms supported on 2D MoS2 (Fe‐MoS2) for the nitrate reduction reaction (NO3RR). Fe‐MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98% for NO3RR to NH3 at an onset potential of −0.48 V versus the reversible hydrogen electrode (RHE) as confirmed by the isotopic nuclear magnetic resonance (NMR) analyses. Density functional theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de‐oxidation of *NO to *N. The catalysts are coupled to an InGaP/GaAs/Ge triple‐junction solar cell to demonstrate a solar‐to‐ammonia (STA) conversion efficiency of 3.4% and a yield rate of 510 µg h−1 cm−2. The results open new avenues for the design of single‐atom catalysts (SAC) for the realization of solar‐driven ammonia production. [ABSTRACT FROM AUTHOR]

MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2–MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol–gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors. [ABSTRACT FROM AUTHOR]