Ag‐induced Phase Transition of Bi(2)O(3) Nanofibers for Enhanced Energy Conversion Efficiency towards Formate in CO(2) Electroreduction

Bi‐based electrocatalysts have been widely investigated in the CO(2) reduction reaction (CO(2)RR) for the formation of formate. However, it remains a challenge to achieve high Faradaic efficiency (FE) and industrial current densities at low overpotentials for obtaining both high formate productivity and energy efficiency (EE). Herein, we report an Ag−Bi(2)O(3) hybrid nanofiber (Ag−Bi(2)O(3)) for highly efficient electrochemical reduction of CO(2) to formate. Ag−Bi(2)O(3) exhibits a formate FE of >90% for current densities from −10 to −250 mA ⋅ cm(−2) and attains a yield rate of 11.7 mmol ⋅ s(−1) ⋅ m(−2) at −250 mA ⋅ cm(−2). Moreover, Ag−Bi(2)O(3) increased the EE (52.7%) by nearly 10% compared to a Bi(2)O(3) only counterpart. Structural characterization and in‐situ Raman results suggest that the presence of Ag induced the conversion of Bi(2)O(3) from a monoclinic phase (α‐Bi(2)O(3)) to a metastable tetragonal phase (β‐Bi(2)O(3)) and accelerated the formation of active metallic Bi at low overpotentials (at > −0.3 V), which together contributes to the highly efficient formate formation.