Large-scale carbon fixation requires high-volume chemicals production from carbon dioxide. Dry reforming of methane could provide an economically feasible route if coke- and sintering-resistant catalysts were developed. Here, we report a molybdenum-doped nickel nanocatalyst that is stabilized at the edges of a single-crystalline magnesium oxide (MgO) support and show quantitative production of synthesis gas from dry reforming of methane. The catalyst runs more than 850 hours of continuous operation under 60 liters per unit mass of catalyst per hour reactive gas flow with no detectable coking. Synchrotron studies also show no sintering and reveal that during activation, 2.9 nanometers as synthesized crystallites move to combine into stable 17-nanometer grains at the edges of MgO crystals above the Tammann temperature. Our findings enable an industrially and economically viable path for carbon reclamation, and the “Nanocatalysts On Single Crystal Edges” technique could lead to stable catalyst designs for many challenging reactions.

Photoelectrochemical overall water splitting without an external bias is demonstrated using an all-bismuth-based oxide tandem cell with a CuBi 2 O 4 photocathode and a BiVO 4 photoanode. A solution-based nitrate salt decomposition method is developed for preparing a crystalline p-type CuBi 2 O 4 film with a suitable band gap and Fermi level to serve as a photocathode for water splitting. The optimum CuBi 2 O 4 photocathode is prepared by three-layer deposition and heat-treatment at 823 K, which yields the highest photocurrent density of −0.66 mA cm −2 at 0.4 V RHE and reduction onset potential of ≥1.0 V RHE under 1 sun in O 2 -purged KPi electrolyte. The all-bismuth based oxide tandem cell of Pt/CuBi 2 O 4 photocathode and a cobalt-phosphate (Co-Pi) modified Mo-doped BiVO 4 photoanode give a photocurrent density of ∼0.15 mA cm −2 without any applied bias.

D´eborah De Masi opened the discussion of the paper by Laura Prati: Can you explain why you have better results with ruthenium nanoparticles than with bimetallic RuAu NPs? Is it due to a change of the crystallinity of Ru when it is on the surface of Au? Laura Prati replied: There is not a direct explanation but we experienced that the synergistic eff ect is not always positive. It depends on the structure, on the electronic distribution, on the matching between reactant, etc. Aldiar Adishev asked: Can you explain how the introduction of gold aff ects reactions tested with bimetallic systems? Or do you have future plans to further study the eff ect of gold? Laura Prati answered: We have seen that Au can have an eff ect on both electronic or geometric eff ects. However the balance between these two factors depends on the structures of the bimetallic particles you are synthesizing. In the case of Pd, for example, we have shown that the eff ect of gold mainly aff ects the O2 interaction with the catalyst thus in turn reducing the occurrence of Pd-O species. Baldassarre Venezia remarked: In this work it has also been emphasized how the Pd/AC and AuPd/AC catalyst were selective in the oxidation of benzyl alcohol to benzaldehyde. However, might this result be due to the low concentration of benzyl alcohol (0.3 M in cyclohexane) employed in the oxidation reaction? The low amount of benzyl alcohol in the autoclave might have hindered the disproportionation reaction of benzyl alcohol into toluene and benzaldehyde, whose kinetics is generally proportional to benzyl alcohol concentration and reaction temperature. Laura Prati responded: Actually we used quite dilute solution (0.3 M). Of course this could have an impact on the selectivity of the reaction. However we established that in the case of AuPd compared to pure Pd there is a decreased adsorption of oxygen on the catalyst surface which can explain a diff erent selectivity. Please refer to previous work in ref. 1 and 2.

Hu and Ruckenstein state that our findings were overclaimed and not new, despite our presentation of evidence for the Nanocatalysts on Single Crystal Edges (NOSCE) mechanism. Their arguments do not take into account fundamental differences between our Ni-Mo/MgO catalyst and their NiO/MgO preparations.

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