The adsorption properties of structurally well defined bimetallic Pt/Ru(0001) surfaces, consisting of a Ru(0001) substrate partly or fully covered by monolayer Pt islands or a monolayer Pt film, were studied by temperature programmed desorption (TPD) using CO and deuterium as probe molecules. Additionally, the adsorption of CO was investigated by infrared reflection absorption spectroscopy (IRAS). The presence of the pseudomorphic platinum islands or monolayer film leads to considerable modifications of the adsorption properties for both adsorbates, both on the Pt covered and, to a smaller extent, on the bare Ru part of the surfaces. In addition to distinct weakly bound adspecies, which are adsorbed on the monolayer Pt islands, we find unique contributions from island edge desorption, from spill-over processes during the desorption run, and a general down-shift of the peak related to desorption from Pt-free Ru(0001) areas with increasing Pt coverage. These effects, which we consider as characteristic for adsorption on bimetallic surfaces with large contiguous areas of the respective types, are discussed in detail.
Water splitting is an environmentally friendly strategy to produce hydrogen but is limited by the oxygen evolution reaction (OER). Therefore, there is an urgent need to develop highly efficient electrocatalysts. Here, NiFe layered double hydroxides (NiFe LDH) with tunable Ni/Fe composition exhibit corresponding dependent morphology, layered structure, and chemical states, leading to higher activity and better stability than that of conventional NiFe LDH-based catalysts. The characterization data show that the low overpotentials (249 mV at 10 mA cm -2 ), ultrasmall Tafel slopes (24 mV dec -1 ), and high current densities of Ni 3 Fe LDH result from the larger fraction of trivalent Fe 3+ and the optimized local chemical environment with more oxygen coordination and ordered atomic structure for the metal site. Owing to the active intermediate species, Ni(Fe)OOH, under OER conditions and a reversible dynamic phase transition during the cycling process, the Ni 3 Fe LDH achieves a high current density of over 2 A cm -2 at 2.0 V, and durability of 400 h at 1 A cm -2 in a single cell test. This work provides insights into the relationship between the composition, electronic structure of the layer, and electrocatalytic performance, and offers a scalable and efficient strategy for developing promising catalysts to support the development of the future hydrogen economy.
The development of novel metal oxide catalysts for electrochemical water splitting has been one of the future challenges in catalysis. We present the development of structured spinel based NiCo2O4 materials using in‐situ hydrothermal synthesis and KIT‐6 as a template. Their electron transfer kinetics in the oxygen evolution reaction (OER) at pH 14 are studied. Structuring of NiCo2O4 via KIT‐6 improves the intrinsic catalyst performance, e. g., a lower overpotential of ∼350 mV and a good long‐term stability could be observed compared to 385 mV and poor stability of commercially available NiCo2O4. Kinetic studies provided insights into structure‐activity relations and the nature of the electrode/electrolyte interface. Interestingly, structuring via KIT‐6 increases not only the electrochemical surface area but also the current density accompanied by superior charge transfer capacity.
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