H2　generation　from　methanol-water　mixtures　often　requires　high　pressure　and　high　temperature　(200–300 °C).　However,　CO　can　be　easily　generated　and　poison　the　catalytic　system　under　such　high　temperature.　Therefore,　it　is　highly　desirable　to　develop　the　efficient　catalytic　systems　for　H2　production　from　methanol　at　room　temperature,　even　at　sub-zero　temperatures.　Herein,　carbon　nanotube-supported　Pt　nanocomposites　are　designed　and　synthesized　as　high-performance　nano-catalysts,　via　stabilization　of　Pt　nanoparticles　onto　carbon　nanotube　(CNT),　for　H2　production　upon　methanol　dehydrogenation　at　sub-zero　temperatures.　Therein,　the　optimal　Pt/CNT　nanocomposite　presents　the　superior　catalytic　performance　in　H2　production　upon　methanol　dehydrogenation　at　the　expense　of　B2(OH)4,　with　the　TOF　of　299.51 min-130　oC.　Compared　with　other　common　carriers,　Pt/CNT　exhibited　the　highest　catalytic　performance　in　H2　production,　emphasizing　the　critical　role　of　CNT　in　methanol　dehydrogenation.　The　confinement　of　Pt　nanoparticles　by　CNTs　is　conducive　to　inhibiting　the　aggregation　of　Pt　nanoparticles,　thereby　significantly　increasing　its　catalytic　performance　and　stability.　The　kinetic　study,　detailed　mechanistic　insights,　and　density　functional　theory　(DFT)　calculation　confirm　that　the　breaking　of　O─H　bond　of　CH3OH　is　the　rate-controlling　step　for　methanol　dehydrogenation,　and　both　H　atoms　of　H2　are　supplied　by　methanol.　Interestingly,　H2　is　also　successfully　produced　from　methanol　dehydrogenation　at　−10 °C,　which　absolutely　solves　the　freezing　problem　in　the　H2　evolution　upon　water-splitting　reaction.　©　2023　The　Authors.　Advanced　Science　published　by　Wiley-VCH　GmbH.