A robust bifunctional catalyst for rechargeable Zn-air batteries: Ultrathin NiFe-LDH nanowalls vertically anchored on soybean- derived Fe-N-C matrix

NiFe layered double hydroxide (NiFe-LDH) nanosheets and metal-nitrogen-carbon materials (M-N-C, M = Ni, Fe, Co, etc.) are supreme catalysts in the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) process, respectively. Nevertheless, the monotonic performance and insufficient stability severely hamper their practical application in rechargeable batteries. Herein, we simultaneously combine ultrathin NiFe-LDH nanowalls with renewable soybean-derived Fe-N-C matrix to obtain a hybrid materials (NiFe-LDH/FeSoy-CNSs-A), which exhibits robust catalytic activities for OER (E_j=10 = 1.53 V vs. RHE) and ORR (E_1/2 = 0.91 V vs. RHE), with a top-notch battery parameters and stability in assembled rechargeable Zn-air batteries. Intensive investigations indicate that the vertically dispersed NiFe-LDH nanosheets, Fe-N-C matrix derived from soybean and the strong synergy between them are responsible for the unprecedented OER and ORR performances. The key role of intrinsic N defects involved in the hybrid materials is firstly specified by ultrasoundassisted extraction of soy protein from soybean. The exquisite design can facilitate the utilization of sustainable biomass-derived catalysts, and the mechanism investigations of N defects and oxygenic groups on the structure-activity relationship can stimulate the progress of other functional hybrid electrocatalysts.