Xi'an Jiaotong University

About: Xi'an Jiaotong University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Heat transfer & Dielectric. The organization has 85440 authors who have published 99682 publications receiving 1579683 citations. The organization is also known as: '''Xi'an Jiaotong University''' & Xi'an Jiao Tong University.

Controllable Design of MoS2 Nanosheets Anchored on Nitrogen-Doped Graphene: Toward Fast Sodium Storage by Tunable Pseudocapacitance

Abstract: Transition-metal disulfide with its layered structure is regarded as a kind of promising host material for sodium insertion, and intensely investigated for sodium-ion batteries. In this work, a simple solvothermal method to synthesize a series of MoS2 nanosheets@nitrogen-doped graphene composites is developed. This newly designed recipe of raw materials and solvents leads the success of tuning size, number of layers, and interplanar spacing of the as-prepared MoS2 nanosheets. Under cut-off voltage and based on an intercalation mechanism, the ultrasmall MoS2 nanosheets@nitrogen-doped graphene composite exhibits more preferable cycling and rate performance compared to few-/dozens-layered MoS2 nanosheets@nitrogen-doped graphene, as well as many other reported insertion-type anode materials. Last, detailed kinetics analysis and density functional theory calculation are also employed to explain the Na+ - storage behavior, thus proving the significance in surface-controlled pseudocapacitance contribution at the high rate. Furthermore, this work offers some meaningful preparation and investigation experiences for designing electrode materials for commercial sodium-ion batteries with favorable performance.

Unified Triple-Phase-Shift Control to Minimize Current Stress and Achieve Full Soft-Switching of Isolated Bidirectional DC–DC Converter

Abstract: This paper presents a comprehensive analysis of the current-stress optimization and soft-switching operation of the isolated bidirectional dual active bridge (DAB) dc–dc converter with the unified triple-phase-shift (UTPS) control. On this basis, the current-stress-optimized modulation scheme is proposed for DAB, which leads to the minimum current stress with the required transmission power and voltage conversion ratio in the whole load range. Moreover, the full soft-switching operation is achieved for the converter simultaneously. Distinct from the previous modulation schemes, the proposed optimized modulation scheme is deduced from a unified analysis of TPS where all effective switching modes are investigated. A novel algorithm based on the Karush–Kuhn–Tucker (KKT) conditions is originally proposed to derive closed-form solutions for the global optimal control parameters. This paper also presents a typical closed-loop control strategy for DAB with TPS control and detailed descriptions about the closed-loop operation. A laboratory prototype is applied, and the experimental results validate that the current-stress optimization and efficiency improvement are realized by applying the optimized modulation scheme. The experimental results also verify the effectiveness of the closed-loop control strategy for DAB with TPS control.

10.8% Efficiency Polymer Solar Cells Based on PTB7‐Th and PC71BM via Binary Solvent Additives Treatment

Abstract: In this work, polymer solar cells are fabricated based on the blend of PTB7-Th: PC71BM by using a mixed solvent additive of 1,8-diiodooctane and N-methyl pyrrolidone to optimize the morphology of the blend. A high power conversion efficiency (PCE) of 10.8% has been achieved with a simple conventional device. In order to deeply investigate the influence of the mixed solvent additives on the morphology and device performance, the variations of the molecular packing and bulk morphology of the blend film cast from ortho-dichlorobenzene with single or binary solvent additives are measured. Although all the blend films exhibit similar domain size and nanoscale phase separation, the blend film processed with mixed solvent additive shows the highest domain purity, resulting in the least bimolecular recombination, relatively high Jsc and FF, and hence enhanced PCE. Therefore, the best photovoltaic performance with the Voc of 0.82 V, Jsc of 19.1 mA cm−2, FF of 69.1%, and PCE of 10.8% are obtained for the device based on the blend with binary solvent additive treatment.

Hexagonal-Phase Cobalt Monophosphosulfide for Highly Efficient Overall Water Splitting.

Abstract: The rational design and synthesis of nonprecious, efficient, and stable electrocatalysts to replace precious noble metals are crucial to the future of hydrogen economy. Herein, a partial sulfurization/phosphorization strategy is proposed to synthesize a nonstoichiometric pyrrhotite-type cobalt monophosphosulfide material (Co0.9S0.58P0.42) with a hexagonal close-packed phase for electrocatalytic water splitting. By regulating the degree of sulfurization, the P/S atomic ratio in the cobalt monophosphosulfide can be tuned to activate the Co3+/Co2+ couples. The synergy between the nonstoichiometric nature and the tunable P/S ratio results in the strengthened Co3+/Co2+ couples and tunable electronic structure and thus efficiently promotes the oxygen/hydrogen evolution reaction (OER/HER) processes toward overall water splitting. Especially for OER, the Co0.9S0.58P0.42 material, featured with a uniform yolk–shell spherical morphology, shows a low overpotential of 266 mV at 10 mA cm–2 (η10) with a low Tafel slope...