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Efficient ammonia synthesis at low temperatures is anticipated for establishing a hydrogen carrier system. We reported earlier that application of an electric field on the Cs/Ru/SrZrO3 catalyst enhanced catalytic ammonia synthesis activity. It is now clear that N2 dissociation is activated by hopping protons in the electric field. Efficient ammonia synthesis proceeds by an "associative mechanism" in which N2 dissociates via an N2H intermediate, even at low temperatures. The governing factor of ammonia synthesis activity in an electric field for active metals differed from that in the conventional mechanism. Also, N2H formation energy played an important role. The effects of dopants (Al, Y, Ba, and Ca) on this mechanism were investigated using activity tests and density functional theory calculations to gain insights into the support role in the electric field. Ba and Ca addition showed positive effects on N2H formation energy, leading to high ammonia synthesis activity. The coexistence of proton-donating and electron-donating abilities is necessary for efficient N2H formation at the Ru–support interface. [ABSTRACT FROM AUTHOR]

Low-temperature heterogeneous catalytic reaction in an electric field is anticipated as a novel approach for on-demand and small-scale catalytic processes. This report quantitatively reveals the important role of proton coverage on the catalyst support for catalytic ammonia synthesis in an electric field, which shows an anti-Arrhenius behaviour. [ABSTRACT FROM AUTHOR]

This is the first direct observation that surface proton hopping occurs on SrZrO3 perovskite even under a H2 (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H2 atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H2 revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H2. H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H2 supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions. [ABSTRACT FROM AUTHOR]

Catalytic methane steam reforming was conducted at low temperature using a Pd catalyst supported on Ce 1- x M x O 2 ( x = 0 or 0.1, M = Ca, Ba, La, Y or Al) oxides with or without an electric field (EF). The effects of the catalyst support on catalytic activity and surface proton hopping were investigated. Results show that Pd/Al-CeO 2 (Pd/Ce 0.9 Al 0.1 O 2 ) showed higher activity than Pd/CeO 2 with EF, although their activity was identical without EF. Thermogravimetry revealed a larger amount of H 2 O adsorbed onto Pd/Al-CeO 2 than onto Pd/CeO 2 , so Al doping to CeO 2 contributes to greater H 2 O adsorption. Furthermore, electrochemical conduction measurements of Pd/Al-CeO 2 revealed a larger contribution of surface proton hopping than that for Pd/CeO 2 . This promotes the surface proton conductivity and catalytic activity during EF application., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Low-temperature heterogeneous catalytic reaction in an electric field is anticipated as a novel approach for on-demand and small-scale catalytic processes. This report quantitatively reveals the important role of proton coverage on the catalyst support for catalytic ammonia synthesis in an electric field, which shows an anti-Arrhenius behaviour.

This is the first direct observation that surface proton hopping occurs on SrZrO 3 perovskite even under a H 2 (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H 2 atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H 2 revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H 2 . H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H 2 supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions.