Enhancing Interfacial Electrocatalysts by Engineering Monomer Composition and Sequence of Metallo-oligomer Monolayers

The hetero-metallo-oligomer monolayers are superior to their monomers for interfacial electrocatalysis but remain unpredictable in synthetic complexity. Here, we present a general strategy to systematically optimize interfacial electrocatalysts by engineering monomer composition and sequence of hetero-oligomer monolayers. These monolayers are prepared by electrochemically sequencing the addition of well-known catalytic complexes Ru(II)-qpyL1L2 (qpy = quaterpyridine, L1 = 9-(4-(pyridin-4-yl) phenyl)-9H-carbazole, L2 = 4-vinylpyridine) and Ru(II)-bdaL1L2 (bda = 2,2'-bipyridine-6,6'-dicarboxylate) onto self-assembled monolayers. The quantitatively engineering conductance, catalytic current densities, and overpotentials are studied as a function of molecular length, composition, and sequence. The catalytic current densities of homo-oligomer monolayers are enhanced by at least 20% as a function of the molecular lengths. The catalytic current density of the alternating hetero-heptamer monolayer is 10 and 2.4 times higher than those of the self-assembled and homo-heptamer monolayers, respectively. Our work opens up a simple and efficient pathway to optimize and enhance the catalytic performance of well-known interfacial molecular materials.