Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen are attractive alternative power supplies for a range of applications, with in situ release of the required hydrogen from a stable liquid offering one way of ensuring its safe storage and transportation 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), so the focus for vehicle and portable PEMFC applications 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. There remains, however, the need for an efficient APRM catalyst. Here we report that platinum (Pt) atomically dispersed on α-molybdenum carbide (α-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 α-MoC to induce water dissociation, and to the fact that platinum and α-MoC act in synergy to activate methanol and then to reform it.

A one-step ligand-free method based on an adsorption-precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO ) nanocatalysts. Ir species demonstrated a strong metal-support interaction (SMSI) with the CeO substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO ) hydrogenation reaction it was shown that the chemical state of Ir species-induced by a SMSI-has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single-site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal-support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub-nano, and atomic scales.

Zn- and Na-modulated Fe catalysts were fabricated by a simple coprecipitation/washing method. Zn greatly changed the size of iron species, serving as the structural promoter, while the existence of Na on the surface of the Fe catalyst alters the electronic structure, making the catalyst very active for CO activation. Most importantly, the electronic structure of the catalyst surface suppresses the hydrogenation of double bonds and promotes desorption of products, which renders the catalyst unexpectedly reactive toward alkenes-especially C5+ alkenes (with more than 50% selectivity in hydrocarbons)-while lowering the selectivity for undesired products. This study enriches C1 chemistry and the design of highly selective new catalysts for high-value chemicals.

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Spin-polarized density functional theory calculations have been performed to investigate the carbon pathways and hydrogenation mechanism for CH(4) formation on Fe(2)C(011), Fe(5)C(2)(010), Fe(3)C(001), and Fe(4)C(100). We find that the surface C atom occupied sites are more active toward CH(4) formation. In Fischer-Tropsch synthesis (FTS), CO direct dissociation is very difficult on perfect Fe(x)C(y) surfaces, while surface C atom hydrogenation could occur easily. With the formation of vacancy sites by C atoms escaping from the Fe(x)C(y) surface, the CO dissociation barrier decreases largely. As a consequence, the active carburized surface is maintained. Based on the calculated reaction energies and effective barriers, CH(4) formation is more favorable on Fe(5)C(2)(010) and Fe(2)C(011), while Fe(4)C(100) and Fe(3)C(001) are inactive toward CH(4) formation. More importantly, it is revealed that the reaction energy and effective barrier of CH(4) formation have a linear relationship with the charge of the surface C atom and the d-band center of the surface, respectively. On the basis of these correlations, one can predict the reactivity of all active surfaces by analyzing their surface properties and further give guides for catalyst design in FTS.

Cu-oxide catalysts have a tendency to deactivate dramatically in reverse water gas shift (RWGS) reaction, because of the aggregation of supported copper particles at high temperatures. Herein, β-Mo2C, which is a typical type of transition-metal carbide, has been demonstrated to be capable of dispersing and stabilizing copper particles. Cu/β-Mo2C catalysts exhibit good catalytic activity and stability for the RWGS reaction. Under relatively high weight hourly space velocity (WHSV = 300 000 mL/g/h), the optimized 1 wt % Cu/β-Mo2C exhibits superior activity over traditional oxide-supported Pt- and Cu-based catalysts. The activity was well-maintained in a 40 h stability test, and the catalyst shows stable reactivity in a six-cycle start-up cool-down experiment. Detailed structure characterizations demonstrate that the strong interaction between Cu and β-Mo2C effectively promotes the dispersion of supported copper and prevents the aggregation of Cu particles, which accounts for the extraordinary activity and stability for the RWGS reaction.

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