Bilayer nanosheets of unusual stoichiometric bismuth oxychloride for potassium ion storage and CO2 reduction

Bilayer-Bi12O17Cl2 nanosheets (BBNs), a kind of unusual stoichiometric bismuth oxychloride, with abundant oxygen vacancies (OVs) were synthesized by a simple but efficient hydrothermal method, and acted as the generalist material for Potassium-ion battery (PIB) anode and CO2 reduction reaction. The BBNs with a thickness of ~1.5 nm offer a large electrode-electrolyte contact interface and a short path for K+ diffusion. Importantly, the abundant OVs not only provide more active sites but also promote ionic transmission and electrical conductivity. As an anode for PIB, it provides a high initial discharge capacity (627.5 mA h g−1 at 500 mA g−1), high rate performance (420 mA h g−1 at 10 A g−1) and outstanding cycle performance (198 mA h g−1 after 1500 cycles at 10 A g−1). When evaluated as the electrocatalyst for CO2 reduction, the BBNs exhibited an impressive activity, selectivity and stability (JHCOO- = 11.5 mA/cm2 at −0.89 V, Faradaic efficiency >92%, and durability for >12 h). Considering the easy preparation, low cost, and fast-kinetics, this promising strategy and associated opportunities demonstrate great potential for energy storage or electrocatalysts.