Long Ren,Jun Chen,Xiaoqing Wang,Mingjia Zhi,Junwei Wu,Xinhe Zhang
Facile synthesis of porous and hollow spinel materials is highly desirable for their extensive applications in energy storage fields. In this work, uniform and decentralized flower-like CoMn2O4 microspheres were synthesized and characterized for supercapacitor electrodes in neutral aqueous electrolyte. In this contribution, uniform microsphere precursors were firstly fabricated by a solvothermal method, followed by a low temperature calcination process for crystallization. A detailed study shows that the deionized (DI) water content plays an important role in the solvothermal process to optimize the morphology of the microspheres. In 1 M Na2SO4, the spinel electrode material has a working potential window as high as 1.1 V and a specific capacitance of 188 F g−1. Besides, the electrode material exhibits excellent cycling stability by retaining 93% of its original capacitance after 1000 cycles. Therefore, the flower-like microspheres of CoMn2O4 spinel are promising candidates for supercapacitor applications.
Rechargeable zinc-air batteries (ZABs) stand out among next-generation battery technologies due to their high energy density and high safety but suffer from electrochemical irreversibility. Herein, we report a hybrid ZAB with a long lifespan and high working voltage; it uses a neutral anolyte, an acidic catholyte, and a proton-shuttle-shielding dual-hydrophobic membrane to isolate the two electrolytes. The hybrid ZAB operates through the stable electrochemical plating and stripping of zinc (Zn) in a neutral anolyte and a high-voltage O 2 redox reaction in acidic catholyte. The designed proton-shuttle-shielding dual-hydrophobic membrane selectively transports hydrophobic bis(trifluoromethylsulfonyl)imide anions (TFSI − ) and effectively avoids the crossover of protons. As a result, the hybrid ZAB exhibits a high working voltage (1.50 V) and stable operation (up to 2,000.0 h) in ambient air. This strategy not only overcomes the severe irreversibility of conventional ZABs but also promotes development of electrolyte-decoupled systems.
Neutral oxygen evolution reaction (OER) is a crucial half-reaction for electrocatalytic chemical production under mild condition, but with limited development due to low activity and poor stability. Herein, a tungsten-doped cobalt molybdate (WDCMO) catalyst was synthesized for efficient and durable OER under neutral electrolyte. It is demonstrated that catalyst reconstruction is suppressed by W doping, which stabilizes the Co-O-Mo point-to-point connection in CoMoO 4 architecture and stimulates to a lower valence state of active sites over the surface phase. Thereby, the surface structure maintains to avoid compound dissolution caused by over-oxidation during OER. Meanwhile, the WDCMO catalyst promotes charge transfer and optimizes *OH intermediate adsorption, which improves reaction kinetics and intrinsic activity. Consequently, the WDCMO electrode exhibits an overpotential of 302 mV at 10 mA cm –2 in neutral electrolyte with an improvement of 182 mV compared with CoMoO 4 electrode. Furthermore, W doping significantly improves the electrode stability from 50 h to more than 320 h, with a suppressive potential attenuation from 2.82 to 0.29 mV h –1 . This work will shed new light on designing rational electrocatalysts for neutral OER.
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