Photocatalytic　CO2　reduction　has　been　regarded　as　an　appealing　pathway　for　CO2　conversion　to　hydrocarbon　fuels.　To　boost　the　CO2　photoreduction　performance,　developing　suitable　cocatalyst　on　the　photocatalysts　is　an　efficient　strategy.　Herein,　Co2N　is　employed　as　novel　noble-metal-free　cocatalyst　to　promote　the　CO2　photoreduction　performance　of　BiOBr　ultrathin　nanosheets.　The　optimal　Co2N/BiOBr　delivers　a　high　selectivity　CO　formation　rate　of　67.8　mu　mol　g(-1)h(-1)　in　pure　water　without　sacrificial　reagent　or　extra　photosensitizer,　roughly　6　times　higher　than　BiOBr.　Co2N　can　create　strong　electronic　interactions　with　BiOBr,　steering　the　electron　transfer　from　BiOBr,　across　the　interface　to　metallic　Co2N　and　finally　to　the　surface.　Apart　from　the　charge　separation　steering,　the　activation　energy　barrier　can　be　lowered　on　Co2N　surface　via　stabilize　COOH*　intermediates,　tuning　the　rate-limiting　step　from　the　formation　of　COOH*　on　BiOBr　to　the　formation　of　CO*　on　Co2N,　jointly　optimize　the　CO2　photoreduction　activity.　This　strategy　affords　an　accessible　pathway　for　designing　cocatalysts　for　efficient　CO2　photoreduction.