N-doped carbon-coated Co_3O_4 nanosheet array/carbon cloth for stable rechargeable Zn-air batteries

N掺杂碳包覆的Co_3O_4纳米片/碳布复合材料用于稳定的可充电Zn空气电池（英文）

Although the application of various nonprecious compounds as the air cathodes of Zn-air batteries has been explored, the construction of highly efficient selfsupported Co-based electrodes remains challenging and highly desired given their outstanding electrocatalytic activity and cost-effectiveness. Herein, we fabricated a three-dimensional(3D) self-supported electrode based on N-doped,carbon-coated Co3O4 nanosheets grown on a carbon cloth(i.e., NC-Co3O4/CC) through the electrochemical deposition and carbonization. When used as a binder-free electrode for oxygen evolution reaction(OER), the NC–Co3O4/CC electrode demonstrated excellent electrocatalytic activity with an overpotential of 210 mV at 10 mA cm^-2 and a Tafel slope of79.6 mV dec^-1. In the Zn-air battery test, the electrode delivered a small charge/discharge voltage gap(0.87 V at 10 mA cm^-2) and exhibited high durability without degradation after 93 cycles at the large current density of 25 mA cm^-2.The durability of our electrode was superior to that of a commercial Pt/C+RuO2 catalyst. The excellent performance of NC–Co3O4/CC could be attributed to the presence of 3D structures that promoted electron/ion transfer. By the absence of a binder, the carbon coating improved electron conductivity and promoted electrochemical stability. Moreover, N doping could be used to adjust the C electron structure and accelerate electron transfer. The present study provides a facile and effective route for the synthesis of various self-supported electrodes that fulfill the requirements of different energy storage and conversion devices.

多种非贵金属化合物已经被用作锌空气电池的正极材料.钴基自支撑电极由于其制备低成本、高性能的优势而具有良好的应用前景,但是构建高效的钴基自支撑电极仍面临很大的挑战.本研究中,我们采用电沉积及后续碳化的方法制备了一种在碳布上生长的氮掺杂碳包覆Co_3O_4纳米片三维复合材料(NC-Co_3O_4/CC).作为自支撑电极用作OER催化剂,在电流密度为10 mA cm^(-2)时过电势为210 mV, Tafel斜率为79.6 mV dec^(-1).作为锌空气电池的正极材料时,在10 mA cm^(-2)的电流密度下其充放电电压差为0.87 V,即使大电流密度为25 mA cm^(-2)时仍然具有良好的稳定性(93次循环后性能没有衰减),远远超过了商业催化剂. NC-Co_3O_4/CC电极优异的性能主要归因于三维结构利于电解液离子的扩散,同时不使用粘结剂也能够增强电极的导电性.另外,碳包覆不仅能够提高电子传导特性,而且能提升电极的电化学稳定性.氮掺杂可以调节碳的电子结构,加速电子的传递.本工作提供了一种简单有效的策略用于合成各种自支撑电极,从而满足不同能量存储及转换器件对电极的需求.