Conductivity-enhanced porous N/P co-doped metal-free carbon significantly enhances oxygen reduction kinetics for aqueous/flexible zinc-air batteries

A novel N/P co-doped porous carbon catalyst (NPPC-950) with high specific surface area was prepared by facile calcination method using ZIF-8 as precursor and red phosphorus as phosphorus source. The low content of P doping can significantly reduce the work function of the catalyst. The catalyst exhibits excellent oxygen reduction performance and has promising application prospect in Zinc-air batteries. [Display omitted] •Red phosphorus was calcined with MOF-derived carbon to obtain N/P co-doped carbon (NPPC-950).•N/P heteroatom doping reduces the work function of NPPC-950 and thus promotes electron transfer.•The PC bond alters the charge and spin density of the C atom, thus providing more active sites.•The catalyst showed excellent oxygen reduction performance close to Pt/C in zinc-air batteries. Heteroatom-doped metal-free carbon catalysts for oxygen reduction reactions have gained significant attention because of their unusual activity and economic cost. Here, a novel N/P co-doped porous carbon catalyst (NPPC) with a high surface area for oxygen reduction reaction (ORR) is constructed by a facile high-temperature calcination method employing ZIF-8 as the precursor and red phosphorus as the phosphorus source. In particular, ZIF-8 is firstly calcined to obtain N-doped carbon (NC) followed by further calcination with red phosphorus to obtain NPPC. Ultraviolet photoelectron spectroscopy (UPS) analysis shows that the ultra-low amount of P doping could significantly decrease the work function from 4.32 to 3.86 eV. The resultant catalyst exhibits a promising electrocatalytic activity with a half-wave potential (E1/2) of 0.87 V and a limiting current density (JL) of 5.15 mA cm−2. Besides, it also shows improved catalytic efficiency and excellent durability with a negligible decay of JL after 2000 CV cycles. Moreover, aqueous and solid-state flexible zinc-air batteries (ZAB) using the catalyst show a promising application potential. This work provides new insight into developing P/N-doped metal-free carbon ORR catalysts.