Bi 2 O 3 /BiO 2 Nanoheterojunction for Highly Efficient Electrocatalytic CO 2 Reduction to Formate.

Heterostructure engineering plays a vital role in regulating the material interface, thus boosting the electron transportation pathway in advanced catalysis. Herein, a novel Bi 2 O 3 /BiO 2 heterojunction catalyst was synthesized via a molten alkali-assisted dealumination strategy and exhibited rich structural dynamics for an electrocatalytic CO 2 reduction reaction (ECO 2 RR). By coupling in situ X-ray diffraction and Raman spectroscopy measurements, we found that the as-synthesized Bi 2 O 3 /BiO 2 heterostructure can be transformed into a novel Bi/BiO 2 Mott-Schottky heterostructure, leading to enhanced adsorption performance for CO 2 and *OCHO intermediates. Consequently, high selectivity toward formate larger than 95% was rendered in a wide potential window along with an optimum partial current density of -111.42 mA cm -2 that benchmarked with the state-of-the-art Bi-based ECO 2 RR catalysts. This work reports the construction and fruitful structural dynamic insights of a novel heterojunction electrocatalyst for ECO 2 RR, which paves the way for the rational design of efficient heterojunction electrocatalysts for ECO 2 RR and beyond.