One A3B Porphyrin Structure-Three Successful Applications

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A3B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by 1H- and 13C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039-6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon-steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A3B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = -10 mA/cm2 and a Tafel slope value of 205 mV/dec.

Guiding the design of oxidation-resistant Fe-based single atom alloy catalysts with insights from configurational space

The high activity and selectivity of Fe-based heterogeneous catalysts toward a variety of reactions that require the breaking of strong bonds are offset in large part by their considerable instability with respect to oxidative deactivation. While it has been shown that the stability of Fe catalysts is considerably enhanced by alloying them with precious metals (even at the single-atom limit), rational design criteria for choosing such secondary metals are still missing. Since oxidative deactivation occurs due to the strong binding of oxygen to Fe and reduction by adsorbed hydrogen mitigates the deactivation, we propose here to use the binding affinity of oxygen and hydrogen adatoms as the basis for rational design. As it would also be beneficial to use cheaper secondary metals, we have scanned over a large subset of 3d-5d mid-to-late transition metal single atoms and computationally determined their effect on the oxygen and hydrogen adlayer binding as a function of chemical potential and adsorbate coverage. We further determine the underlying chemical origins that are responsible for these effects and connect them to experimentally tunable quantities. Our results reveal a reliable periodic trend wherein oxygen binding is weakened greatest as one moves right and down the periodic table. Hydrogen binding shows the same trend only at high (but relevant) coverages and otherwise tends to have its binding slightly increased in all systems. Trends with secondary metal coverage are also uncovered and connected to experimentally tunable parameters.

High-throughput calculations of catalytic properties of bimetallic alloy surfaces

A comprehensive database of chemical properties on a vast set of transition metal surfaces has the potential to accelerate the discovery of novel catalytic materials for energy and industrial applications. In this data descriptor, we present such an extensive study of chemisorption properties of important adsorbates - e.g., C, O, N, H, S, CHx, OH, NH, and SH - on 2,035 bimetallic alloy surfaces in 5 different stoichiometric ratios, i.e., 0%, 25%, 50%, 75%, and 100%. To our knowledge, it is the first systematic study to compile the adsorption properties of such a well-defined, large chemical space of catalytic interest. We propose that a collection of catalytic properties of this magnitude can assist with the development of machine learning enabled surrogate models in theoretical catalysis research to design robust catalysts with high activity for challenging chemical transformations. This database is made publicly available through the platform www.Catalysis-hub.org for easy retrieval of the data for further scientific analysis.

Graph Theory Approach to High-Throughput Surface Adsorption Structure Generation

We present a methodology for graph based enumeration of surfaces and unique chemical adsorption structures bonded to those surfaces. Utilizing the graph produced from a bulk structure, we create a unique graph representation for any general slab cleave and further extend that representation to include a large variety of catalytically relevant adsorbed molecules. We also demonstrate simple geometric procedures to generate 3D initial guesses of these enumerated structures. While generally useful for generating a wide variety of structures used in computational surface science and heterogeneous catalysis, these techniques are also key to facilitating an informatics approach to the high-throughput search for more effective catalysts.

Strategies of alloying effect for regulating Pt-based H2-SCR catalytic activity

Alloying Pt with 3d transition metals results in the d-band center moving away from the Fermi level, creating compressive strain. The adsorption strength of the reactants should not be too strong or too weak. The presence of compressive strain, which can increase the orbital overlap between *H and *O, results in the reduction of energy barriers of H-assisted N-O bond activation in terms of the Langmuir-Hinshelwood (L-H) reaction route. Our findings provide guidelines to design more efficient H2-SCR catalysts.