Interfacial Molecular Engineering of Cobalt Catalysts Enables Efficient Bifunctional Electrocatalysis.

Abstract

Molecularly defined bifunctional electrocatalysts that operate efficiently across a broad pH range remain a formidable challenge in electrocatalysis. Herein, we present a rationally designed hybrid system that systematically disentangles the distinct roles of molecular anchoring and support functionalization-a critical but previously overlooked distinction in carbon-based electrocatalyst design. By noncovalently immobilizing cobalt-cyclen complexes bearing either aromatic (benzyl) or aliphatic side chains onto carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), we construct molecular-carbon interfaces that allow the relationship between molecular structure and catalytic activity to be examined. The benzyl-functionalized Co(12-TBC)/MWCNTs-COOH hybrid delivers exceptional bifunctional performance, outperforming its aliphatic analog by a striking 358 mV reduction in hydrogen evolution reaction (HER) overpotential at -10 mA cm-2 (η10) in neutral media, alongside significantly enhanced oxygen evolution reaction (OER) activity. Remarkably, this hybrid maintains impressive activity across acidic (η10 = 161 mV for HER, 283 mV for OER) and alkaline (343/359 mV) conditions, underscoring its pH-universal versatility. Comprehensive electrochemical studies show that surface carboxylation increases accessible active-site density and improves intrinsic catalytic activity and interfacial electron-transfer characteristics. This work highlights interfacial molecular organization as an important design parameter and validates noncovalent immobilization as a scalable, broadly applicable strategy for advanced molecular electrocatalysis.

Abstract as supplied by the indexing source. © the authors / publisher.