Electrocatalytic　carbon　dioxide　reduction　reaction　(CO2RR)　toward　value-added　fuels　has　attracted　increasing　attention　in　carbon-neutral　and　energy-production　fields,　but　the　catalytic　efficiency　is　seriously　hindered　by　the　robust　linear　scaling　relations　between　adsorption　energies　of　intermediates.　Herein,　we　have　extensively　investigated　the　effect　of　a　series　of　group　B,　B,　and　B　transition　metal　(TM)　atoms　substitution　for　middle　Mo　in　Mo3C2　MXene　on　the　catalytic　performance　of　CO2RR.　Our　results　suggest　that　the　captured　CO2　can　be　selectively　reduced　to　methane　(CH4)　on　both　Mo3C2　and　Mo2TMC2　bimetal　MXenes.　We　highlight　that　TM　substitution　can　significantly　reduce　the　limiting　potential　(UL)　of　CO2RR　from　−0.651　V　(Mo3C2)　to　−0.350　V　(Mo2TiC2)　by　decreasing　the　Gibbs　energy　difference　of　rate-determining　step　(OCH2O*　+　H++e-=　HOCH2O*).　The　modulation　mechanism　is　illuminated　that　TM　substitution　in　Mo3C2　MXene　gives　rise　to　the　upshift　of　d-band　center　of　Mo　atoms,　which　selectively　tunes　the　adsorption　strength　of　OCH2O*　and　HOCH2O*,　resulting　in　breaking　their　linear　scaling　relations.　Further　analyses　on　electron　localization　function　(ELF)　visualize　the　TM　substitution　induced　stronger　surface　localization　lone　electrons,　which　endows　the　surface　Mo　with　promoted　chemical　activity.　The　dynamical　stability　of　Mo2TiC2　has　been　well　verified　by　phonon　dispersion　curves　and　ab　initio　molecular　dynamics　(AIMD)　simulations,　suggesting　the　robust　stability　of　Mo2TiC2　as　an　electrocatalyst　for　CO2RR.　Our　findings　pave　the　way　of　MXenes　for　CO2　capture　and　pioneer　the　application　of　Mo2TiC2　as　a　novel　and　efficient　catalyst　for　CO2　to　CH4.　©　2021　Elsevier　B.V.