Bi ₂ Se ₃ /Bi ⁰ Composite Nanoplates as a CO ₂ Reduction Electrocatalyst for Formic Acid Production

ABSTRACT Bismuth metal and its oxides are common catalysts for electrochemical CO 2 reduction (CO 2 R) to HCOOH, although they tend to suffer from lower activity due to poor conductivity. Here we investigated a bismuth selenide catalyst which adopted a spiral‐nanoplate morphology. The catalyst had a mass activity of 31 mA mg −1 for HCOOH at ‐0.9 V RHE, double that of commercial Bi 2 Se 3 powder, nearly ten‐times that of commercial Bi (16 mA mg −1 and 3.8 mA mg −1 respectively), and competitive with other contemporary Bi‐based catalysts. It also possessed greater stability than these counterparts. The higher mass activity of spiral Bi 2 Se 3 occurred alongside a lower charge transfer resistance (78 Ω) than commercially available Bi 2 Se 3 or Bi (314 Ω and 247 Ω respectively). These characteristics of spiral Bi 2 Se 3 were attributed to the presence of a unique Bi 2 Se 3 /Bi 0 heterostructure formed from the depletion of Se from the near‐surface region of the material during electrocatalysis. The lower charge transfer resistance of the Bi 2 Se 3 /Bi 0 heterostructure, relative to Bi and commercial Bi 2 Se 3 , resulted in catalytic sites that were more active for the kinetically complex CO 2 R reaction.