Research Article Issue
Highly efficient and stable electrocatalyst for hydrogen evolution by molybdenum doped Ni-Co phosphide nanoneedles at high current density
Nano Research 2024, 17 (3): 1066-1074
Published: 26 July 2023

There is an increasingly urgent need to develop cost-effective electrocatalysts with high catalytic activity and stability as alternatives to the traditional Pt/C in catalysts in water electrolysis. In this study, microspheres composed of Mo-doped NiCoP nanoneedles supported on nickel foam were prepared to address this challenge. The results show that the nanoneedles provide sufficient active sites for efficient electron transfer; the small-sized effect and the micro-scale roughness enhance the entry of reactants and the release of hydrogen bubbles; the Mo doping effectively improves the electrocatalytic performance of NiCoP in alkaline media. The catalyst exhibits low hydrogen evolution overpotentials of 38.5 and 217.5 mV at a current density of 10 mA·cm−2 and high current density of 500 mA·cm−2, respectively, and only 1.978 V is required to achieve a current density of 1000 mA·cm−2 for overall water splitting. Density functional theory (DFT) calculations show that the improved hydrogen evolution performance can be explained as a result of the Mo doping, which serves to reduce the interaction between NiCoP and intermediates, optimize the Gibbs free energy of hydrogen adsorption ( ΔG*H), and accelerate the desorption rate of *OH. This study provides a promising solution to the ongoing challenge of designing efficient electrocatalysts for high-current-density hydrogen production.

Research Article Issue
Insight into the influence of ether and ester electrolytes on the sodium-ion transportation kinetics for hard carbon
Nano Research 2023, 16 (8): 10922-10930
Published: 29 June 2023

The electrochemical performance of hard carbon (HC) materials is closely related to the electrolyte used in the sodium ion batteries (SIBs). Conventional electrolytes carbonate (EC) demonstrates low initial Columbic efficiency (ICE) and poor rate performance, which is one of the main bottlenecks that limits the practical application of HCs. Ether electrolyte (diglyme) was reported to improve the rate performance of HCs. Nevertheless, the underlying mechanism for the excellent rate capability is still lack of in-depth study. In this work, the differences of sodium-ion diffusion between ether and carbonate-base electrolytes in HCs are analyzed layer by layer. Firstly, when sodium-ions are diffused in electrolyte, the diffusion coefficient of sodium-ion in ether electrolyte is about 2.5 times higher than that in ester electrolytes by molecular dynamics (MD) simulation and experimental characterization. Furthermore, when the solvated sodium-ions are diffused into the solid electrolyte interphase (SEI) interface and the HCs material, the enhanced charge transfer kinetics (thin SEI layer (4.6 vs. 12 nm) and low RSEI (1.5 vs. 24 Ω)) at the SEI combined with low desolvation energy (0.248 eV) are responsible for high-rate performance and good cycling stability of HC in ether electrolyte. Therefore, high diffusion coefficient, low desolvation energy, and good interface are the intrinsic reasons for enhanced rate performance in ether electrolyte, which also has guiding significance for the design of other high-rate electrolytes.

Review Article Issue
Recent advances in semimetallic pnictogen (As, Sb, Bi) based anodes for sodium ion batteries: Structural design, charge storage mechanisms, key challenges and perspectives
Nano Research 2021, 14 (11): 3690-3723
Published: 24 March 2021

In the recent times sodium ion batteries (SIBs) have come to the forefront as an economic and resourceful alternative to lithium-ion batteries (LIBs) for powering portable electronic devices and large-scale grid storage. As the specific capacity, energy density and long cycle life of batteries depend upon the performance of anode materials; their quest is the ultimate need of the hour. Among the anode materials, the semimetallic pnictogens (As, Sb, Bi) and their compounds offer high gravimetric/volumetric capacities, but suffer from undesired volume expansion and inferior electrical conductivity. Herein, this paper reviews the recent progress in semimetallic pnictogens as alloying anodes and their compounds mainly as conversion-alloying anodes. Various debatable sodiation mechanisms (intercalation or alloying) have been presented with emphasis on in situ/ex situ advanced characterization methods well supported by theoretical modeling and calculations. The reviewed electrochemical reaction mechanisms, coherent structural designs and engineering provide a vital understanding of the electrochemical processes of Na+ ion storage. The existing challenges and perspectives are also presented, and several research directions are proposed from the aspects of special morphological design, employing conductive substrates, electrolyte additives and reducing particle size for technical and commercial success of SIBs.

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