Neutral-Condition Hydrogen Peroxide Electrosynthesis at Industrial-Level Current Density Over Bipyridine-Bridged Cobalt-Based Conductive Metal-Organic Frameworks.

Abstract

Conductive metal-organic frameworks (c-MOFs) have been widely adopted for catalyzing two-electron oxygen reduction reaction (2e- ORR) toward hydrogen peroxide (H2O2) electrosynthesis, due to their precisely designable metal-nonmetal coordinations. However, the π-π conjugated c-MOFs normally possess a fairly small interlayer spacing, leaving their internal active sites unexposed and thus severely limiting their catalytic capability. Herein, by combining the theoretical prediction based on density functional theory calculations with experimental verification, bipyridine (BPY)-bridged and Co porphine-based c-MOF (BPY-Co-TCPP, TCPP = tetra(4-carboxyphenyl)-porphine) has been designed, in which the BPY ligands remarkably expand the interlayer spacing of the Co-TCPP, thereby efficiently enabling the exposure of internal active sites for 2e- ORR electrocatalysis. In addition, BPY ligands also create extra axial-N coordination for the CoN4 and Co2O8 sites in Co-TCPP, which finely tunes the electronic properties of Co centers and further optimizes their catalytic activities. Consequently, the as-synthesized BPY-Co-TCPP achieves a stable H2O2 yield at an industrial-level current density of 300 mA cm-2 in neutral media with a high Faradaic efficiency of ∼90%. Meanwhile, the as-produced H2O2 solution shows confirmed potential for water purification and disinfection. These findings highlight the effectiveness of precise bridging strategy in optimizing the catalytic capability of layered electrocatalysts, paving the way for highly efficient H2O2 electrosynthesis and other chemical transformations.