Microbial　fuel　cells　(MFCs)　are　a　promising　biotechnology　that　realizes　the　transformation　of　wastewater　treatment　from　an　energy　consumption　to　an　electricity　generation　process.　However,　the　tedious　process　and　the　large　resources　consuming　in　preparing　powder　ORR　catalysts　are　still　non-negligible　limiting　factors　for　application.　This　study　aims　at　proposing　an　energy-efficient　method　for　preparing　three-dimensional　binder-free　air　cathode　for　MFCs:　non-noble　composite　catalysts　based　on　graphene　and　MnO2　are　synthesized　directly　on　stainless　steel　fiber　felt　(SSFF)　by　pre-fixing　and　electro-reducing　graphene　oxide　on　SSFF　(rGO-SSFF),　and　then　in-situ　depositing　MnO2　nanocatalysts　on　rGO-SSFF　(rGO@MnO2-SSFF).　The　experimental　results　show　that　the　ORR　ability　of　rGO@MnO2-SSFF　cathode　is　greater　than　that　of　Pt/C-CC　cathode,　even　if　the　performance　of　rGO@MnO2　powder　catalyst　is　slightly　lower　than　that　of　the　traditional　Pt/C　catalyst.　The　excellent　performance　is　found　to　be　due　to　the　three-dimensional　framework-pore　structure　of　SSFF　which　helps　the　prepared　cathode　possess　larger　electrochemical　active　area　(8415.18　m(2)　m(-3))　than　Pt/C-CC　cathode　(7518.13　m(2)　m(-3)).　The　proposed　method　provides　a　new　way　to　reduce　the　cost　(labor,　materials　and　energy)　of　air　cathode　while　ensuring　the　high　electricity　output　of　MFCs.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.