Enriching surface-ordered defects on WO 3 for photocatalytic CO 2 -to-CH 4 conversion by water.

Defect engineering has been widely applied in semiconductors to improve photocatalytic properties by altering the surface structures. This study is about the transformation of inactive WO 3 nanosheets to a highly effective CO 2 -to-CH 4 conversion photocatalyst by introducing surface-ordered defects in abundance. The nonstoichiometric WO 3- x samples were examined by using aberration-corrected electron microscopy. Results unveil abundant surface-ordered terminations derived from the periodic {013} stacking faults with a defect density of 20.2%. The {002} surface-ordered line defects are the active sites for fixation CO 2 , transforming the inactive WO 3 nanosheets into a highly active catalyst (CH 4 : O 2 = 8.2: 16.7 μmol h -1 ). We believe that the formation of the W-O-C-W-O species is a critical step in the catalytic pathways. This work provides an atomic-level comprehension of the structural defects of catalysts for activating small molecules.