ABSTRACT
The exploration and development of self-powered visible-blind ultraviolet photodetectors (VBUV PDs) with high responsivity and wavelength selectivity have far-reaching significance for versatile applications. Although In2O3 shows potential for UV detection due to good UV absorption and electrical transport properties, the poor wavelength selectivity impedes further application in VBUV PDs. Here, a self-powered photoelectrochemical-type (PEC) VBUV PD is demonstrated by using gallium-indium oxide alloys (Ga-In OAs). The self-powered Ga-In OAs-based PEC VBUV PDs exhibit good VBUV photodetection performance, including a high responsivity of 50.04 mA/W and a high detectivity of 6.03 × 1010 Jones under 254 nm light irradiation, a good wavelength selectivity (UV/visible light rejection ratio of 262.45), and a fast response time (0.45/0.38 s). The good self-powered VBUV detection performance of Ga-In OAs is attributed to the larger band gap and smaller charge-transfer resistance induced by alloy engineering, which not only suppresses the absorption of visible light but also accelerates interfacial charge transfer. Moreover, an underwater optical communication system is demonstrated by using the self-powered Ga-In OAs PEC VBUV PDs. This study demonstrates that alloy engineering is a powerful tool to improve the performance of In2O3-based PEC PDs, and Ga-In OAs have great application potential for underwater optoelectronic devices.
ABSTRACT
TiO2 and WO3 are two of the most important, industrially relevant earth-abundant oxides. Although both materials show complementary functionality and are promising candidates for similar types of applications such as catalysis, sensor technology, and energy conversion, their chemical stability in reactive environments differs remarkably. In this study, anodic barrier oxides are grown on solid-solution W xTi1- x alloy precursors covering a wide compositional range (0 ≤ x ≤ 1) with the goal of creating functional oxides with tailored stability. A strong Ti-cation enrichment in the surface region of the grown W xTi1- xO n layer is observed, which can be controlled by both the anodizing conditions and precursor composition. For Ti concentrations above 50 at. %, a continuous nanometer-thick TiO2 protective coating is achieved on top of a homogeneous W xTi1- xO n film as evidenced by X-ray photoelectron spectroscopy and transmission electron microscopy analyses. A comprehensive electrochemical assessment demonstrates a very stable passivation of the surface in both acidic and alkaline environments. This increase in chemical stability correlates directly with the presence of this protective TiO2 film. The results of this work provide insights into the oxidation behavior of W1- xTi x alloys, but more importantly demonstrate how controlled oxidation of self-passivating alloys can lead to oxide alloys with thin, protective surface layers that otherwise would require more sophisticated deposition methods.
ABSTRACT
Exploiting high-efficiency and low-cost bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been actively encouraged because of their potential applications in the field of clean energy. In this paper, we reported a novel electrocatalyst based on an exfoliated two-dimensional (2D) MXene (Ti3C2T x) loaded with bimetallic oxide alloy nanoparticles (NPs) of Pt and Pd (represented by PtO aPdO bNPs@Ti3C2T x), which was synthesized via solution plasma (SP) modification. The prepared materials were then utilized as highly efficient bifunctional electrocatalysts toward the HER and OER in alkaline solution. At a high plasma input power (200 W), bimetallic oxide alloy nanoparticles of Pt and Pd or nanoclusters with different metallic valence states were deposited onto the Ti3C2T x nanosheets. Because of the synergism of the noble-metal NPs and the Ti3C2T x nanosheets, the electrocatalytic results revealed that the as-prepared PtO aPdO bNPs@Ti3C2T x nanosheets under the plasma input power of 200 W for 3 min only required a low overpotential to attain 10 mA cm-2 for the HER (-26.5 mV) in 0.5 M H2SO4 solution and OER (1.54 V) in 0.1 M KOH solution. Moreover, water electrolysis using this catalyst achieved a water splitting current density of 10 mA cm-2 at a low cell voltage of 1.53 V in 1.0 M KOH solution. These results suggested that the hybridization of the extremely low usage of PtO a/PdO b NPs (1.07 µg cm-2) and Ti3C2T x nanosheets by SP will expand the applications of other clean energy reactions to achieve sustainable energy.