Bismuth oxyformate@polypyrrole nanowires: synergy of confined reconstruction and enhanced mass transfer for efficient and durable electrochemical CO2 reduction

Abstract

The electrochemical CO2 reduction reaction (eCO2RR) to formate presents a promising route for carbon utilization. Bismuth-based catalysts are highly selective for this conversion, but suffer from limited mass transport and uncontrollable reconstruction. Herein, we harness reconstruction to predictively design an advanced core-shell nanowires pre-catalyst, in which bismuth oxyformate (BiOCOOH) nanowires are encapsulated by a hydrophobic polypyrrole (PPy) layer. During the reductive eCO2RR process, BiOCOOH is spontaneously reduced to metallic Bi and reassembles inside the PPy shell, preserving the nanowire morphology while creating a void structure between Bi and PPy due to volume shrinkage. This configuration not only suppresses morphology changes and active-site leaching during electrochemical reconstruction, but also promotes efficient CO2 and proton transfer through reconstruction-induced voids. Consequently, the catalyst delivers exceptional eCO₂RR performance in both H-type and flow cells, achieving formate selectivity exceeding 90% and a maximum formate partial current density of 511 mA cm−2. Importantly, it shows remarkable long-term durability of 614 h at combined current densities of 20 and 200 mA cm−2, as well as 241 h at an industrial-level current density of 500 mA cm−2. This work highlights the synergy of controllable reconstruction and enhanced mass transfer toward efficient and durable eCO2RR.