Self-Powered Water-Splitting Devices by Core-Shell NiFe@N-Craphite-Based Zn-Air Batteries

摘要

Development of highly efficient and low-cost multifunctional electrocatalysts for the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR), and the hydrogen evolution reaction is urgently required for energy storage and conversion applications, such as in Zn-air batteries and water splitting to replace very expansive noble metal catalysts. Here, the new core-shell NiFe@ N-graphite electrocatalysts with excellent electrocatalytic activity and stability toward OER and ORR are reported and the Ni0.5Fe0.5@ N-graphite electrocatalyst is applied as the air electrode in Zn-air batteries. The respective liquid Zn-air battery shows a large open-circuit potential of 1.482 V and a small charge-discharge voltage gap of 0.12 V at 10 mA cm(-2), together with excellent cycling stability even after 40 h at 20 mA cm(-2). Interestingly, the all-solid-like Zn-air battery thus derived shows a highly desired mechanical flexibility, whereby little change is observed in the voltage when bent into different angles. Using the same Ni0.5Fe0.5@ N-graphite electrode, a self-driven water-splitting device, which is powered by two Zn-air batteries in-series, is constructed. The present study opens a new opportunity for the rational design of metal@N-graphite-based catalysts of core-shell structures for electrochemical catalysts and renewable energy applications.