Doping　metal　ions　into　cobalt　sulfide　is　a　promising　strategy　to　improve　its　performance　as　a　cheap,　green,　highly　active　and　sustainable　electrocatalyst　for　overall　water　splitting.　Herein,　cauliflower-like,　noble　metal-free　bifunctional　electrocatalysts　composed　of　S,　N,　and　O　atoms　co-incorporated　porous　carbon　(SNOPC)　encapsulated　Fe　doped　Co9S8　nanoparticles　are　successfully　synthesized　by　direct　pyrolysis　of　S,　Co,　and　Fe-based　polypyrrole　(S–Co–Fe-PPYs)　precursors　for　efficient　overall　water　splitting.　Specifically,　the　optimal　catalyst　(Fe0-33-Co9S8@SNOPC)　shows　excellent　electrocatalytic　performance　in　an　alkaline　electrolyte,　requiring　ultra-low　overpotentials　of　275　and　258　mV　to　reach　a　current　density　of　10　mA　cm−2　for　oxygen　evolution　reaction　(OER)　and　hydrogen　evolution　reaction　(HER),　respectively,　with　exceptional　stability　for　50　h.　Furthermore,　when　applied　for　overall　water　splitting　as　a　bifunctional　electrolyzer,　it　generates　a　current　density　of　10　mA　cm−2　at　an　extremely　low　cell　voltage　of　1.595　V.　The　exceptional　electrocatalytic　activity　of　Fe0-33-Co9S8@SNOPC　can　be　credited　to　the　synergistic　effect　produced　by　Fe　doped　Co9S8　core　and　multi-atom　incorporated　porous　carbon　shell.　©　2023　Elsevier　Ltd