Application of Graphene-Combined Rare-Earth Oxide (Sm2O3) in Solar-Blind Ultraviolet Photodetection

Rare-earth oxide Sm2O3 is theoretically expected to be used in the preparation of ultraviolet (UV) detectors with low dark currents and high radiation resistance due to its characteristics of a wide bandgap, a high dielectric constant, and high chemical stability. However, certain features that rare-earth oxides possess, such as high resistivity and weak photoelectric response currents, have hindered relevant research on these kinds of materials in the field of UV detection. In this work, a p-Gr/i-Sm2O3/n-SiC heterojunction photovoltaic solar-blind UV sensor was constructed for the first time. Because of the high mobility of graphene (Gr) and the contribution of double built-in electric fields in the heterojunction, the collection efficiency of photogenerated carriers has been greatly improved, with the typical shortcomings of high resistivity and poor photoelectric response performance of rare-earth oxides having been overcome. This detector has exhibited outstanding performance at 0 V, including a responsivity of 19.8 mA/W and an open-circuit voltage of 0.68 V. Additionally, this detector has a detectivity as high as 1.2 × 1011 jones, which is at the front position of most ultraviolet detectors. The fabrication of this high-performance Sm2O3-based photovoltaic UV detector has broadened the application fields of rare-earth oxide semiconductors. Therefore, this project has important value for future research in relevant fields.

Nanoparticle-Decorated Ultrathin La2O3 Nanosheets as an Efficient Electrocatalysis for Oxygen Evolution Reactions

Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial applications. Here, we report a rare-earth metal-based oxide electrocatalyst comprised of ultrathin amorphous La₂O₃ nanosheets hybridized with uniform La₂O₃ nanoparticles (La₂O₃@NP-NS). Significantly improved OER performance is observed from the nanosheets with a nanometer-scale thickness. The as-synthesized 2.27-nm La₂O₃@NP-NS exhibits excellent catalytic kinetics with an overpotential of 310 mV at 10 mA cm^-2, a small Tafel slope of 43.1 mV dec^-1, and electrochemical impedance of 38 Ω. More importantly, due to the ultrasmall thickness, its mass activity, and turnover frequency reach as high as 6666.7 A g^-1 and 5.79 s^-1, respectively, at an overpotential of 310 mV. Such a high mass activity is more than three orders of magnitude higher than benchmark OER electrocatalysts, such as IrO₂ and RuO₂. This work presents a sustainable approach toward the development of highly efficient electrocatalysts with largely reduced mass loading of precious elements.

Nanoscale analysis of the oxidation state and surface termination of praseodymium oxide ultrathin films on ruthenium(0001)

The complex structure and morphology of ultrathin praseodymia films deposited on a ruthenium(0001) single crystal substrate by reactive molecular beam epitaxy is analyzed by intensity-voltage low-energy electron microscopy in combination with theoretical calculations within an ab initio scattering theory. A rich coexistence of various nanoscale crystalline surface structures is identified for the as-grown samples, notably comprising two distinct oxygen-terminated hexagonal Pr₂O₃(0001) surface phases as well as a cubic Pr₂O₃(111) and a fluorite PrO₂(111) surface component. Furthermore, scattering theory reveals a striking similarity between the electron reflectivity spectra of praseodymia and ceria due to very efficient screening of the nuclear charge by the extra 4f electron in the former case.