Rechargeable aqueous zinc-ion batteries (ZIB) are emerging as one promising alternative for Li-ion batteries on account of the high energy density, environmental friendliness, rich earth abundance and good safety characteristics. Nevertheless, almost all the ZIBs suffer from sluggish kinetics of Zn 2+ diffusion in electrodes, leading to poor rate capability and inadequate cycle life in practical applications. To tackle this issue, herein we develop an in situ polyaniline (PANI) intercalation strategy to facilitate the Zn 2+ (de)intercalation kinetics in V2O5. In this way, a remarkably enlarged interlayer distance (13.90 Å) can be constructed alternatively between the V-O layers, offering expedite This article is protected by copyright. All rights reserved.3 channels for facile Zn 2+ diffusion. More importantly, the electrostatic interactions between Zn 2+ and host O 2-, which is another key factor in hindering the Zn 2+ diffusion kinetics, can be effectively blocked by the unique π-conjugated structure of PANI. As a result, the PANI-intercalated V2O5 exhibits a stable and highly reversible electrochemical reaction during repetitive Zn 2+ insertion and extraction, as demonstrated by in situ synchrotron X-ray diffraction and Raman studies. Further first-principles calculations clearly reveal a remarkably lowered binding energy between Zn 2+ and host O 2+ , which explains the favorable kinetics in PANI-intercalated V2O5. Moreover, the intercalation of PANI leads to an intermediated energy band lying across the Fermi level, thereby offering a step for electron transport during charging/discharging process. Benefitting from the above, the overall electrochemical performance of PANI-intercalated V2O5 electrode has been remarkable improved, exhibiting excellent high rate capability of 197.1 mAh g −1 at current density of 20 A g −1 with capacity retention of 97.6% over 2000 cycles. Our approach presents a prospective guideline for the electrode design of high performance aqueous ZIBs, which could be also expanded to widespread battery researches.

cathode materials with superior high-rate, long-term cycling and low-temperature performance.Herein, we report a facile microwave-assisted strategy for the synthesis of interlayer Mn 2+ -doped hydrated layered vanadium oxide (Mn 0.15 V 2 O 5 ·nH 2 O). The interlayer doping of Mn 2+ ions and structural water can synergistically improve the electronic conductivity, ion mobility and structural stability of layered V 2 O 5 . When used as cathode for ZIBs, the as-prepared Mn 0.15 V 2 O 5 ·nH 2 O electrode performs excellent zinc-ion storage performance in terms of high specific capacity (367 mAh g −1 at a current density of 0.1 A g −1 ), superior rate performance (153 mAh g −1 at high current density up to 10 A g −1 ) and prolonged cycling stability (8000 cycles). Even at a low temperature of −20 °C, a high specific capacity of 100 mAh g −1 can be achieved after 3000 cycles, which endows the Mn 0.15 V 2 O 5 ·nH 2 O materials with more possibility in the practical applications. Moreover, the zinc-ion storage mechanism in the Mn 0.15 V 2 O 5 ·nH 2 O electrode has been revealed by ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis.

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 (CoSP) 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 Co/Co couples. The synergy between the nonstoichiometric nature and the tunable P/S ratio results in the strengthened Co/Co 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 CoSP material, featured with a uniform yolk-shell spherical morphology, shows a low overpotential of 266 mV at 10 mA cm (η) with a low Tafel slope of 48 mV dec as well as high stability, which is comparable to that of the reported promising OER electrocatalysts. Coupled with the high HER activity of CoSP, the overall water splitting is demonstrated with a low η at 1.59 V and good stability. This study shows that phase engineering and composition control can be the elegant strategy to realize the Co/Co couple activation and electronic structure tuning to promote the electrocatalytic process. The proposed strategy and approaches allow the rational design and synthesis of transition metal monophosphosulfides toward advanced electrochemical applications.

The development of novel non-noble electrocatalysts with controlled structure and surface composition is critical for efficient electrochemical hydrogen evolution reaction (HER). Herein, the rational design of porous molybdenum carbide (β-Mo 2 C) spheres with different surface engineered structures (Co doping, Mo vacancies generation, and coexistence of Co doping and Mo vacancies) is performed to enhance the HER performance over the β-Mo 2 C-based catalyst surface. Density functional theory calculations and experimental results reveal that the synergistic effect of Co doping with Mo vacancies increases the electron density around the Fermi-level and modulates the d band center of β-Mo 2 C so that the strength of the MoH bond is reasonably optimized, thus leading to an enhanced HER kinetics. As expected, the optimized Co 50 -Mo 2 C-12 with porous structure displays a low overpotential (η 10 = 125 mV), low-onset overpotential (η onset = 27 mV), and high exchange current density (j 0 = 0.178 mA cm −2 ). Furthermore, this strategy is also successfully extended to develop other effective metal (e.g., Fe and Ni) doped β-Mo 2 C electrocatalyst, indicating that it is a universal strategy for the rational design of highly efficient metal carbide-based HER catalysts and beyond.