Salt assisted fabrication of lignin-derived Fe, N, P, S codoped porous carbon as trifunctional catalyst for Zn-air batteries and water-splitting devices

Exploring inexpensive, effective, and robust multifunctional catalysts for simultaneously catalyzing oxygen reductive reduction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is critical to the practical application of high-efficiency zinc-air batteries and water-splitting devices. Herein, trifunctional catalyst by coupling FeNx, FePx into N, P, S codoped carbon framewrok (Fe-N-C/FePx/NPSC) can be realized via salt assisted strategy by using sodium hypophosphite as the salt template and sodium ligninsulfonate chelated with iron element as the precursor. The Fe-N-C/FePx/NPSC with large specific surface area (782 m2 g−1), high pore volume (0.52 cm3 g−1) and multiple active sites exhibits excellent catalytic performances for ORR (E1/2 = 0.9 V), OER (Ei=10 = 370 mV in alkaline solution) and HER (Ei=10 = 125/198 mV in acidic/alkaline solution). The Zn-air battery based on Fe-N-C/FePx/NPSC displays a high power density of 216.88 mW cm−2 and strong stability, and the water-splitting electrolyzer assembled by Fe-N-C/FePx/NPSC only needs 1.57 V to reach 10 mA cm−2, which are better than those of Pt/C + IrO2 based devices. The flexible Zn-air batteries assembled by Fe-N-C/FePx/NPSC exhibit high reliability under various deformation conditions, proving the potential for application in wearable devices. This work provides a potential way to design multifunctional carbon based electrocatalysts by using sustainable biomass precursors.