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Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen are attractive alternative power supplies for a range of applications1-3, with in situ release of the required hydrogen from a stable liquid offering one way of ensuring its safe storage and transportation4,5 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 applications9 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 stacks10,11. There remains, however, the need for an efficient APRM catalyst. Here we report that platinum (Pt) atomically dispersed on [alpha]-molybdenum carbide ([alpha]-M°C) 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 [alpha]-M°C to induce water dissociation, and to the fact that platinum and [alpha]-M°C act in synergy to activate methanol and then to reform it.
Pioneering work from 15 years ago12,13 showed that hydrogen can be generated by aqueous-phase reforming of biomass-derived carbohydrates, including methanol, on platinum/aluminium oxide catalysts. More recently, use of a single nuclear [RuHCl(CO)(HN(C2H4PiPr2)2)] homogenous catalyst14 enabled hydrogen to form at an unprecedented rate of4,700 mol hydrogen per mol ruthenium per hour in the presence of concentrated potassium hydroxide solution and neat methanol at around 368 K. One main advantage of such homogeneous catalysts14,15, and of metalloenzymes16, is that each metal site in the catalyst contributes directly to the reaction-a fact that has stimulated much work on dispersing catalytically active noble metals as isolated metal atoms on support materials, to improve the efficiency of heterogeneous catalysts while minimizing the amount of noble metal used17-19. However, in order to achieve a high rate of hydrogen production from the reaction of methanol and water at low temperatures, both the water and the methanol must be activated effectively, and this may...