Engineering a sulfur/oxygen-modified bismuth catalyst via dynamic reconstruction of Bi₂OS₂ for efficient CO₂...

The electrochemical conversion of CO₂ to formate using renewable electricity is a promising carbon-neutral technology, yet designing catalysts that simultaneously achieve high activity, selectivity, and durability remains a challenge. In this work, we report a bismuth oxysulfide (Bi₂OS₂) catalyst with an intrinsic layered structure that consists of [BiS₂]^- layers and [Bi₂O₂]²⁺ layers. Beyond providing highly active BiO bonds, the stable [Bi₂O₂]²⁺ layer acts as an atomic anchor that effectively locks trace sulfur species in the final active sites. The experimental results show that Bi₂OS₂ achieves a formate Faradaic efficiency of 90.1% at -0.88 V vs. RHE and maintains stable operation for 100 h. In the flow cell, Bi₂OS₂ retains >90% efficiency over a wide current range of -50 to -400 mA cm^-2. This work not only presents a high-performance catalyst but also introduces a precursor-guided strategy for constructing multi-anion stabilized active sites, offering a generalizable pathway to advanced CO₂ reduction electrocatalysts.