Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen are attractive alternative power supplies for a range of applications(1-3), with in situ release of the required hydrogen from a stable liquid offering one way of ensuring its safe storage and transportation(4,5) before use. The use of methanol is particularly interesting in this regard, because it is inexpensive and can reform itself with water to release hydrogen with a high gravimetric density of 18.8 per cent by weight. But traditional reforming of methanol steam operates at relatively high temperatures (200-350 degrees Celsius)(6-8), so the focus for vehicle and portable PEMFC applications(9) has been on aqueous-phase reforming of methanol (APRM). This method requires less energy, and the simpler and more compact device design allows direct integration into PEMFC stacks(10,11). There remains, however, the need for an efficient APRM catalyst. Here we report that platinum (Pt) atomically dispersed on a-molybdenum carbide (alpha-MoC) enables low-temperature (150-190 degrees Celsius), base-free hydrogen production through APRM, with an average turnover frequency reaching 18,046 moles of hydrogen per mole of platinum per hour. We attribute this exceptional hydrogen production-which far exceeds that of previously reported low-temperature APRM catalysts-to the outstanding ability of a-MoC to induce water dissociation, and to the fact that platinum and a-MoC act in synergy to activate methanol and then to reform it.