Ranxi Liang,Chaozhu Shu,Anjun Hu,Minglu Li,Zhiqun Ran,Ruixin Zheng,Jianping Long
The sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics greatly limit the development of lithium-oxygen (Li-O 2 ) batteries. Therefore, developing efficient electrocatalysts with high stability to boost oxygen involved reactions is particularly important for promoting the application of Li-O 2 batteries. Here, CoSe 2 @NiSe 2 heterostructure with distinct heterogeneous interfaces was fabricated via deliberate interface engineering. The formation of heterogeneous interface promotes local fine atomic array distortion that can act as an additional active site of ORR/OER. In addition, CoSe 2 @NiSe 2 with a distinct heterogeneous interface is favorable for the formation of built-in electric field during charging/discharging to enable electrodes with fast electrical transfer rates and reaction kinetics. Synergistically, the additional active sites brought by the fine atomic array distortion are highly conducive to the reversible formation and decomposition of the product. Undoubtedly, batteries with CoSe 2 @NiSe 2 exhibit excellent discharge/charge capacity (3530.1 mA h g −1 and 3485.6 mA h g −1 ), low overpotential (1.21 V) and excellent electrochemical stability for over 1200 h.
Jia Wang,De Wang,Zelin Zhao,Ganggang Chang,Wei Guo,Jun Xu,Yinyu Xiang,Junrui Li,Junsheng Li
Developing cost-effective ruthenium (Ru)-based HER electrocatalysts as alternatives to commercial Pt/C is crucial for the advancement of proton exchange membrane water electrolysis (PEMWE). However, the strong hydrogen adsorption of Ru-based catalysts restricts its activity. Herein, a strategy is reported to tune the electronic structure and improve mass transfer by implanting Ru atoms onto the (002) facet of two-dimensional zeolitic imidazolate framework-67 (Ru@ L ZIF (002) ) to optimize the d -band center ( ε d ) of Ru and the hydrogen spillover behavior. Benefiting from the ultrathin nanosheet structure and optimized ε d of Ru, the over-strong H adsorption energy is weakened and the electron/mass transfer is facilitated. Ru@ L ZIF (002) exhibits an overpotential of 9.2 mV at 10 mA cm −2 and a long-lasting stability of 35 days at 100 mA cm −2 . The mass activity and price activity of Ru@ L ZIF (002) is 2.9 and 14.7 times higher than Pt/C, respectively. More impressively, Ru@ L ZIF (002) delivers a cell voltage of 2.01 V at a high current density of 4 A cm −2 in PEMWE. The excellent long-term durability of 1200 hours operating at 4 A cm −2 with an ultralow decay rate of 7.5 × 10 −3 mV h −1 has been achieved, making it promising as a cost-effective alternative to Pt/C catalyst for PEMWE applications.
Bo Lv,Sha Zeng,Wei Yang,Jian Qiao,Chao Zhang,Chengfeng Zhu,Minghai Chen,Jiangtao Di,Qingwen Li
Recently, the development of high-performance bifunctional oxygen catalysts integrated with flexible conductive scaffolds for rechargeable metal-air batteries has attracted considerable interest, driving by fast-growing wearable electronics . Herein, we report a flexible bifunctional oxygen catalyst thin film consisting of Co–N–C bifunctional catalysts embedding in carbon nanotube (CNT) networks. The catalyst is readily prepared by pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIF-67) that are in-situ synthesized in CNT networks. Such catalyst film demonstrates very high catalytic activities for oxygen reduction (onset potential: 0.91 V, and half-wave potential: 0.87 V vs. RHE) and oxygen evolution (10 mA cm −2 at 1.58 V) reactions, high methanol tolerance property, and long-term stability (97% current retention). Moreover, our integrated catalyst film shows very good structure flexibility and robustness. Based on the obtained film air electrodes, flexible Zn–air batteries demonstrate low charging and discharging overpotentials (0.82 V at 1 mA cm −1 ) and excellent structure stability in the bending tests . These results indicate that presently reported catalyst films are potential air electrodes for flexible metal–air batteries.
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