ABSTRACT
The built-in electric field (BEF) has become an effective means of adjusting the electronic structure and hydrogen spillover to influence the adsorption of intermediates. However, the previously reported BEF cannot be tuned continuously and precisely. Herein, a series of nanocatalysts with interstitial BEF were successfully synthesized, and the effect of precisely tuned interstitial BEF on the intermediate's adsorption and hydrogen spillover was systematically investigated using changing the insertion of interstitial B. Three catalysts with different BEF strengths were obtained by changing the interstitial content (B0.22-Cu/NC, B0.30-Cu/NC, B0.41-Cu/NC), and it was demonstrated that B0.30-Cu/NC gave the best catalytic performance for hydrogen evolution reactions (HERs). The turnover frequency (TOF) value is shown to reach 0.36 s-1 at just -0.1 V vs. RHE, which is about 3 times that of Cu (0.12 s-1). For the HER, it is one of the best Cu-based catalysts reported to date (Table S3). Besides, when the catalyst was applied to the cathode of the PEM water electrolyzer, B0.30-Cu/NC exhibited long-time stability at a water-splitting current density of 500 mA cm-2. Density functional theory and in situ Raman spectroscopy suggest that a suitable interstitial BEF can not only optimize the intermediate's adsorption but also promote hydrogen spillover.
ABSTRACT
A highly efficient catalyst for Li-O2 batteries based on Ru and MnFe phosphides nanoparticles entrapped in a MnFe Prussian blue analogue (PBA) substrate (Ru-MnFeP/PBA) was explored. Synergy between homogeneous Ru and MnFe phosphides nanoparticles improved the catalytic activity and alleviated side reactions. The Li-O2 battery based on Ru-MnFeP/PBA exhibited excellent performance.
Subject(s)
Electric Power Supplies , Ferrocyanides , Electrodes , Ions , LithiumABSTRACT
Low-cost non-noble metal nanoparticles are promising electrocatalysts that can catalyze oxygen evolution reaction (OER). Various factors such as poor activity and stability hinder the practical applications of these materials. The electroactivity and durability of the electrocatalysts can be improved by optimizing the morphology and composition of the materials. Herein, we report the successful synthesis of hollow porous carbon (HPC) catalysts loaded with ternary alloy (FeCoNi) nanoparticles (HPC-FeCoNi) for efficient OER. HPC is firstly synthesized by a facile carbon deposition method using the hierarchical porous zeolite ZSM-5 as the hard template. Numerous defects are generated on the carbon shell during the removal of zeolite template. Subsequently, FeCoNi alloy nanoparticles are supported on HPC by a sequence of impregnation and H2 reduction processes. The synergistic effect between carbon defects and FeCoNi alloy nanoparticles endows the catalyst with an excellent OER performance (low overpotential of 219 mV; Tafel slope of 60.1 mV dec-1) in a solution of KOH (1 M). A stable potential is maintained during the continuous operation over 72 h. The designed HPC-FeCoNi presents a platform for the development of electrocatalysts that can be potentially applied for industrial OER.
ABSTRACT
Although aqueous Zn-ion batteries (aZIBs) have garnered significant attention, they are yet to be commercialized due to severe corrosion and dendrite growth on Zn anodes. In this work, an artificial solid-electrolyte interface (SEI) with amorphous structure was created in-situ on the anode by immersing Zn foil in ethylene diamine tetra(methylene phosphonic acid) sodium (EDTMPNA5) liquid. This facile and effective method provides the possibility for Zn anode protection in large-scale applications. Experimental results, combined with theoretical calculations, indicate that the artificial SEI remains intact and adheres tightly to the Zn substrate. The negatively-charged phosphonic acid groups and disordered inner structure offer adequate sites for rapid Zn2+ transference and facilitate [Zn(H2O)6]2+ desolvation during charging/discharging. Due to the synergistic effect of the aforementioned advantages, the artificial SEI endows high Coulombic efficiency (CE, 99.75%) and smooth Zn deposition/stripping under the SEI. The symmetric cell exhibits a long cycling life of over 2400 h with low-voltage hysteresis. Additionally, full cells with MVO cathodes demonstrate the superiority of the modified anodes. This work provides insight into the design of in-situ artificial SEI on the Zn anode and self-discharge suppression to expedite the practical application of aZIBs.
ABSTRACT
Photocatalytic water splitting over semiconductors is believed as a promising avenue to obtain H2 fuel from renewable solar energy. However, developing highly active and non-noble-metal photocatalysts for H2 evolution is still quite challenging to date. In this work, by constructing nanosheet-based nanotubes with Cd-doping and S vacancies, a highly improved visible-light-driven H2 production for ZnIn2S4 is achieved. Unlike nanoflowers aggregated with nanosheets, the nanosheet-assembled hierarchical nanotubes allow multiple scattering and reflection of incident light within the interior space, leading to an enhanced light-harvesting efficiency. Together with the benefits from Cd doping and S-vacancy engineering, including narrowed band gaps, efficient transmission and separation of charge carriers, abundant catalytically active sites, heightened photo-stability and photo-electron reduction capacity, as well as a strong electrostatic attraction to protons, the synthesized S-deficient CdxZn1-xIn2S4 hierarchical nanotubes exhibit an extraordinary photocatalytic H2 evolution capability under visible-light irradiation, delivering an outstanding H2-generation activity of 28.99 mmol·g-1·h-1 (corresponding to an apparent quantum yield of 37.1% at 400 nm), which is much superior to that of CdxZn1-xIn2S4 nanoflowers, Pt-loaded ZnIn2S4 nanotubes, and most ever reported ZnIn2S4-based photocatalysts. Our study could inspire the development of low-cost and high-performance photocatalysts via rational structural design and optimization.