Rechargeable Zinc–Air Batteries with Seawater Electrolyte and Cranberry Bean Shell-Derived Carbon Electrocatalyst

Zinc-air batteries with seawater electrolyte utilize abundant andcheap resources. However, it requires an electrocatalyst with high bifunctionalactivity in seawater. In this work, a carbon electrocatalyst is obtained via one-steppyrolysis of the shell waste of cranberry beans. During the oxygen reduction reaction(ORR) in seawater electrolyte, the cranberry bean shell-derived carbon catalystexhibits an ORR onset potential of 0.69 V vs RHE and an ORR saturating currentdensity of 2.93 mA cm-2, which are promising compared to the ORR performanceof Pt/C in seawater electrolyte (0.78 V vs RHE and 3.15 mA cm-2). During OER(oxygen evolution reaction) in seawater electrolyte, the carbon catalyst shows anoverpotential of 582 mV at 5 mA cm-2, 35 mV smaller than the commercial Ir/Ccatalyst (617 mV). Furthermore, when the catalyst is applied to the zinc-air batterywith seawater electrolyte, the cell is able to exhibit discharge and charge voltages of0.93 and 2.2 V, respectively, which are stable for more than 120 cycles of the cyclingtest. This work highlights the fabrication of metal-air batteries with cost-effective and sustainable resources