Carbon-Doping as Efficient Strategy for Improving Photocatalytic Activity of Polysilicon Supported Pd in Hydrogen Evolution from Formic Acid

Interest in cost-effective materials pushes researchers to the inexpensive and abundant semiconductors to use photons’ energy for generating electrons and holes required for photocatalytic transformations. At the same time, polysilicon is one of the economic semiconductors with a disadvantage of high bandgap which could be solved by carbon-doping. We employed this strategy to the synthesis of carbon-doped polysilicon by a new approach starting from citric acid and methyltrimethoxysilane. The nanocomposite obtained was utterly characterized, and compared with bare polysilicon; increased UV–Vis absorbance and shift to higher wavelengths were the most notable characteristics of the synthesized catalyst. The carbon-doped polysilicon was modified with Pd nanoparticles to obtain a new heterogeneous photocatalyst for the formic acid degradation. The decomposition of formic acid was photocatalyzed by the obtained nanocomposite with a hydrogen production turnover frequency of up to 690 h−1. Moreover, it was demonstrated that the catalyst is stable and recyclable.

Effects of carbon doping on structure and magnetocaloric properties of Mn1.25Fe0.7P0.5Si0.5 alloys

(Mn,Fe)2(P,Si)-basedmaterials are promisingly applied in the room-temperature magnetic refrigeration field. In this study, Mn1.25Fe0.7P0.5Si0.5Cx (x = 0, 0.01, 0.03 and 0.05) alloys were prepared by arc-melting and then a two-stage sintering process. The effects of C doping on the crystal structure and magnetocaloric behavior are discussed. Results indicate that the Fe2P-type structure (space group of P62 m) was crystallized for all samples with weakened first-order magnetic transitions (FOMT). The Curie temperature could be altered from 223.5 K to 278.5 K with the large magnetocaloric effect (MCE) remaining by C doping. In the applied magnetic field of 5 T, the peak value of magnetic entropy change (–ΔS M) increased by 7.3% to reach 25.1 J × kg–1 × K–1. The temperature-induced entropy change (ΔS DSC) derived from DSC was slightly larger than ΔS M induced by the magnetic field. The Mn1.25Fe0.7P0.5Si0.5 alloys with large MCE can be effectively tuned by C doping because C atoms prefered to share the substitute and occupy the interstitial sites in hexagonal Fe2P-type structure.

Investigation on Dynamic Characteristics of AlGaN/GaN Lateral Schottky Barrier Diode

This work investigates the transient characteristics of an AlGaN/GaN lateral Schottky barrier diode (SBD) and its recovery process with a dedicated dynamic measurement system. Both static and dynamic characteristics were measured, analyzed with the consideration of acceptor/donor traps in the C-doped buffer and GaN channel, and verified by Silvaco TCAD (technology computer aided design) simulations. The energy band, electric field, and electron concentration were monitored in the transient simulation to study the origin of the current collapse in the SBD. Using the verified model, the impact of carbon doping concentration in the buffer and the thickness of the unintentionally doped (UID) GaN channel in the transient behavior was estimated. Several observations were revealed. Firstly, the traps in the GaN channel and buffer layer have a significant impact on the current collapse of the device. A severe deterioration of current collapse can be observed in the SBDs with increasing density of acceptor-like traps. Secondly, the current collapse increases with the thinner UID GaN channel layer. This well-performed simulation model shows promise to be utilized for the dynamic performance optimization of GaN lateral devices.