Combinatorial Search for High‐Activity Hydrogen Catalysts Based on Transition‐Metal‐Embedded Graphitic Carbons. Issue 23 (22nd September 2015) - Choi, Woon Ih
Abstract : Transition metal (TM) atoms in porphyrin‐like complexes play important roles in many protein and enzymetic systems, where crystal‐field effects are used to modify d‐orbital levels. Inspired by the tunable electronic structure of these motifs, a high‐throughput computational search for synthetic hydrogen catalysts is performed based on a similar motif of TM atoms embedded into the lattice of graphene. Based on an initial list of 300 possible embedding geometries, binders, and host atoms, descriptors for stability and catalytic activity are applied to extract ten promising candidates for hydrogen evolution, two of which are expected to exhibit high activity for hydrogen oxidation. In several instances, the active TM atoms are earth‐abundant elements that show no activity in the bulk phase, highlighting the importance of the coordination environment in tuning the d‐orbitals. In addition, it is found that the most active candidates involve a hitherto unreported surface reaction pathway that involves a Kubas‐complex intermediate, which significantly lowers the kinetic barrier associated with hydrogen dissociation and association Abstract : A new class of hydrogen catalysts and their mechanistic reaction pathway are proposed using high‐throughput computational screening. Ten promising materials are identified from a combinatorial candidate pool of 300 transition‐metal‐embedded graphitic carbons using descriptor‐based assessments of stability and activity. The identified catalysts feature a Kubas‐type coordination on the active sites that lead to improved kinetics for hydrogen evolution.