Electrocatalytic　nitrogen　reduction　reaction　(NRR)　is　widely　considered　a　promising　and　environmentally　sustainable　ammonia　synthesis　strategy　under　ambient　conditions,　yet　the　competitive　hydrogen　evolution　reaction　(HER)　impedes　the　N2　to　NH3　conversion　efficiency.　In　this　work,　carbon-supported　Mo-doped　SnO2　nanoparticles　(Mo-SnO2/C)　with　a　unique　tubular　structure　were　designed　to　suppress　free　water　adsorption,　thereby　reducing　the　competing　HER　and　improving　the　NRR　performance.　The　optimized　Mo-SnO2/C-3　exhibits　a　high　NH3　yield　of　24.03　mu　gh-1mgcat　-1　and　Faradaic　efficiency　of　7.11%　at　-0.8　V　vs　RHE　in　0.1　M　Na2SO4.　The　transient　photovoltage　further　reveals　that　limiting　the　rapid　transfer　of　slow　electrons　effectively　suppresses　the　kinetically　preferred　HER　process.　In　addition,　in　situ　attenuated　total　reflection　surface-enhanced　infrared　absorption　spectroscopy　further　elucidated　that　the　formation　of　a　tubular　carbon　layer　structure　improves　the　hydrophobicity　of　the　catalyst,　weakens　the　adsorption　of　the　interfacial　water　molecules,　and　inhibits　proton　transport,　which　also　realizes　the　inhibition　of　HER　and　improves　the　selectivity　of　NRR.　This　study　highlights　that　limiting　the　slow　electron　transport　strategy　may　inform　the　advancement　of　efficient　and　highly　selective　electrocatalysts.