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[Display omitted] • Effect Mn promotion Co-catalyzed Fischer-Tropsch reaction strongly pressure dependent. • MnO dispersed on Co metal particles provides additional sites for CO dissociation. • Mn raises selectivity at low pressure and promotes CO dissociation not chain growth. • At low pressure, Mn enhances activity and C 5+ selectivity. • At high pressure, Mn enhances activity but lowers C 5+ selectivity. The mechanism of Mn promotion of a silica-supported Co catalyst in the Fischer-Tropsch reaction has been studied at varying pressures up to 20 bar. IR spectroscopy in combination with DFT calculations suggest adsorbed CO is activated by reaction with an oxygen vacancy in the MnO, which covers the Co surface. This leads to a higher activity, higher CH x coverage and thus higher C 5+ and lower CH 4 selectivity. Increasing the pressure magnifies the selectivity differences. However, above around 4 bar, the effect of Mn on the selectivities is reversed and the C 5+ selectivity is decreased by Mn addition. This is tentatively attributed to Mn promoting the C-O bond dissociation but not the chain growth. Formed monomers have to migrate to stepped sites for chain growth on the Co surface. Whilst this is migration is not impeded by co-adsorbates at low pressure, migration could be hindered by especially the high CO coverage at high pressure. [ABSTRACT FROM AUTHOR]

• Fe 3 Co@NG-C shows excellent ORR activity in alkaline solution. • Fe 3 Co@NG-C exhibits enhanced durability and tolerance to methanol. • The activity of Fe 3 Co@NG-C is determined by the strain in N-doped graphene. Nitrogen-doped graphene is a promising non-precious metal electrocatalyst for the oxygen reduction reaction (ORR). We report that distorted nitrogen-doped graphene layers encapsulating Fe 3 Co nanoparticles supported on carbon (Fe 3 Co@NG-C) display excellent activity toward ORR in alkaline media. Compared with a commercial Pt/C electrocatalyst at a loading of 80 μg Pt /cm2 on a rotating disk electrode, the Fe 3 Co@NG-C exhibits an onset potential positively shifted by 50 mV at 0.1 mA/cm2 and a nearly identical half-wave potential. The Fe 3 Co@NG-C has minimal activity degradation during accelerated durability testing and superior tolerance to methanol than commercial Pt/C. Density functional theory calculations combined with poisoning experiments reveal that the high activity of the Fe 3 Co@NG-C mainly arises from strain in nitrogen-doped graphene induced by encapsulation of Fe 3 Co nanoparticles with exposed (1 1 0) planes, which promotes stabilization of the key OOH* intermediate involved in ORR. Our study shows the rational design of improved carbon-based electrocatalysts for ORR can be achieved by using strain engineering. [ABSTRACT FROM AUTHOR]

The replacement of platinum group metals by non-noble metals has attracted significant attention in the field of three-way catalysis. Here, we use DFT calculations to comprehensively study NO reduction by CO and CO oxidation on Pd(1 1 1) and transition metal doped Pd(1 1 1). Whilst direct NO dissociation is very difficult on metallic Pd(1 1 1), doping with transition metals can substantially lower the reaction barrier for NO dissociation. The lowest barrier is predicted for Ti-doped Pd(1 1 1). An electronic structure analysis shows that the low barrier is due to the strong adsorption of N and O on surface sites involving Ti atoms. It relates to strong hybridization of the N and O orbitals with the half-filled d -band of the metallic surface. At the same time, the anti-bonding states are shifted above the Fermi level, which further strengthens the adsorption of N and O. A Brønsted-Evans-Polanyi relation for NO dissociation on TM-doped Pd(1 1 1) surfaces is identified. The complete reaction pathway for N 2 , N 2 O and CO 2 formation on Pd(1 1 1) and Ti-doped Pd(1 1 1) was considered. Besides more facile NO dissociation, the energy barrier for CO oxidation is decreased for the Ti-doped surface. Microkinetics simulations confirm that the activity and selectivity for NO reduction and CO oxidation are drastically improved after Ti doping. Our findings indicate that doping of Pd with non-noble metal can further improve the performance of three-way catalysts. [ABSTRACT FROM AUTHOR]