LAUSR

The helical Bi 2 O 3 microfibers (HBM) were prepared with the assistant of cotton template through a simple heating treatment in air. This twisted structure induced the lattice strains, enriched the oxygen vacancies of Bi 2 O 3 and promote the sufficient exposure of active sites simultaneously, thus perform outstanding activity and selectivity as catalyst for CO 2 electroreduction to formate. The Faradaic efficiency (FE) of formate reaches 100.4% (±1.9%) at -0.90 V vs. reversible hydrogen electrode (RHE) in an H-cell and the partial current density was boosted to 226 mA cm -2 with FE formate of 96% at -1.08 V vs. RHE in a flow cell. This work may open a new era for construction of metal oxide fibers by bionic strategy as high-performance electro- catalysts.