Partial Phase Transition to Construct Amorphous-Crystalline Heterophase Catalyst for Enhanced CO₂ Photoreduction

Amorphous/crystalline catalysts can effectively integrate the advantages of both phases, overcoming the low active site density in crystalline phases and the poor charge separation in amorphous ones. In this work, we report an alkali salt-assisted partial phase transition strategy to synthesize amorphous/crystalline CoMnO_x-400 nanosheets for photocatalytic CO₂ reduction. As a result, the as-prepared CoMnO_x-400 demonstrates superior CO production performance (146.09 µmol g^-1 h^-1, 93.6% selectivity), significantly outperforming amorphous CoMnO_x-260 (66.65 µmol g^-1 h^-1) and crystalline CoMnO_x-500 (89.52 µmol g^-1 h^-1). Supported by systematic characterizations, we propose that the high efficiency of CoMnO_x-400 is attributed to two factors: (i) the charge migration between amorphous and crystalline phases across the seamless contact interface can enhance charge separation efficiency, and (ii) the amorphous domains can provide abundant surface defective active sites for CO₂ adsorption and activation. This work highlights the critical role of phase engineering, particularly the construction of amorphous/crystalline structures, in advancing solar-driven catalytic applications.