In situ simultaneously integrating Co-N-C sites and Co9S8 nanoparticles into N,S-doped porous carbon as trifunctional electrocatalysts for Zn-air batteries driving water splitting

Developing cost-effective, but efficient and stable trifunctional catalysts synchronously for oxygen reduction (ORR), oxygen evolution (OER) and hydrogen evolution reaction (HER) under same electrolytes is essential for the real application of renewable energy systems. Herein, we report the synthesis of a cheap and high-efficiency electro-catalyst based on Co9S8 nanoparticles decorated with Co-N-C sites well anchored to metal-porous organic polymer (MPOP)-derived N, S-codoped carbon (Co-IM-POP-1000), which exhibits pronounced trifunctional electrocatalytic activity for ORR, OER and HER, simultaneously, in alkaline media. Consequently, breathing Zn-air batteries (ZABs) employing Co-IM-POP-1000 as the sole catalysts present prominent performance, i. e., the charge/discharge voltage, power and energy density, specific capacity, rate performance as well as the lifetime, outperforming that of Pt/C 20% + RuO2 counterparts, which could be regenerated and maintained at the same performance level for subsequent runs by simply replenishing the Zn anode and electrolyte. An alkaline water splitting system using the IM-POP-Co-1000 as catalyst for overall water splitting affords a cell voltage as low as 1.60 V at 10 mA cm(-2). A self-driven water splitting system powered by the home-made ZABs is demonstrated using IM-POP-Co-1000 as the sole catalyst in 0.1 M KOH, giving a high H-2 evolution rate of 0.244 mmol h(-1). These novel metal-POPs provides an effective strategy to prepare high-performance POPs for special applica-tions. Therefore, this study shows a promising approach for the utilization of low cost and massive producible POPs as precursor for the preparation of stable and efficient trifunctional electro-catalyst toward clear energy applications.