p-Block Bismuth Nanoclusters Sites Activated by Atomically Dispersed Bismuth for Tandem Boosting Electrocatalytic Hydrogen Peroxide Production.

Constructing electrocatalysts with p-block elements is generally considered rather challenging owing to their closed d shells. Here for the first time, we present a p-block-element Bi-based catalyst derived from a bismuth-based metal-organic framework featuring a high O coordination number (Bi-MOF) for the highly selective O2 reduction reaction (ORR) into hydrogen peroxide (H2O2). Aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption spectroscopy (XAS) revealed the co-existence of single-atomic Bi coordinated with O and S atoms and Bi nanoclusters (Biclu) (collectively denoted as BiOSSA/Biclu). Compared with control samples comprising Bi single atoms or nanoclusters, the catalyst with such a unique structure gives a high selectivity for 2e- reduction (maximum up to 95%) in RRDE test, and a large current density (36 mA cm-2 at 0.15 V vs. RHE), a considerable H2O2 yield with high H2O2 Faraday efficiency (11.5 mg cm-2 h-1 with FE ~ 90% at 0.3 V vs. RHE) and a long-term durability (~22 h) in H-cell test. Interestingly, the experimental data on site poisoning and theoretical calculations both revealed that, for BiOSSA/Biclu, the catalytic active sites are on the Bi clusters, which are further activated by the atomically dispersed Bi coordinated with O and S atoms.