To address the low capacity and poor stability of aqueous zinc–iodine batteries owing to the insulating nature of iodine and the shuttle effect of polyiodide, herein, tungsten nitride-modified porous carbon polyhedron (W2N/N-C) was prepared via the pyrolysis of ZIF-8 injected with phosphotungstic acid (PTA@ZIF-8). During the thermal treatment process, the self-nitridation enabled the in situ formation of tungsten nitride nanoparticles in hierarchical porous carbon with nitrogen doping for favorable loading of iodine. When used as the electrode material, the zinc–iodine battery exhibited the low polarization during the charge/discharge process with improved reversibility and good cycling stability for 2000 cycles. The improved electrochemical performance would be attributed to the confinement effect of W2N/N-C for the reversible conversion between iodine and polyiodide, thus enhancing the redox reversibility and utilization of active materials. The present work demonstrates an efficient strategy to prepare porous carbon with metal nitrides via the combination of carbonization and self-nitridation process for high-performing zinc–iodine battery.
Changcun Tang,Jiahui Liao,Yanzhe Sheng,Yanhe Xiao,Baochang Cheng,Shuijin Lei
The growth of base-metal-based heterostructures on metal-free carriers is considered an effective strategy for designing low-cost high-efficiency hybrid electrocatalysts with electronic modulation for bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as further overall water splitting (OWS). Herein, Ni/Ni 3 N heterostructures with regulable composition are grown in-situ on N-defective graphitic carbon nitride (g-C 3 N 4 ) through a novel ammonia-free topochemical self-nitridation route. Benefitting from the synergetic effect between Ni/Ni 3 N heterointerface and the strong support of g-C 3 N 4 carrier, the as-fabricated Ni/Ni 3 N/g-C 3 N 4 composite performs superior capacity toward both HER and OER in alkaline conditions. The optimal Ni/Ni 3 N/g-C 3 N 4 sample requires low overpotentials for HER (55 mV) and OER (253 mV) to drive a current density of 10 mA cm −2 , along with long-term durability. Furthermore, the constructed Ni/Ni 3 N/g-C 3 N 4 (+||−) electrolytic cell for alkaline OWS can afford a current density of 10 mA cm −2 under a voltage of 1.556 V with outstanding stability.
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