Steering Catalytic Activity and Selectivity of CO2 Photoreduction to Syngas with Hydroxy-Rich Cu2 S@ROH -NiCo2 O3 Double-Shelled Nanoboxes.

Simultaneous transformation of CO2 and H2 O into syngas (CO and H2 ) using solar power is desirable for industrial applications. Herein, an efficient photocatalyst based on double-shelled nanoboxes, with an outer shell of hydroxy-rich nickel cobaltite nanosheets and an inner shell of Cu2 S (Cu2 S@ROH -NiCo2 O3 ), is prepared via a multistep templating strategy. The high performance of Cu2 S@ROH -NiCo2 O3 (7.1 mmol g-1 h-1 for CO; 2.8 mmol g-1 h-1 for H2 ) is attributed to the hierarchical hollow geometry and p-n heterojunction to promote light absorption and charge separation. Spectroscopic and theoretical analyses elucidate that the ROH -NiCo2 O3 surface enhances *CO2 adsorption and lowers energy barriers for CO2 -to-CO. Therefore, modulating the hydroxy contents of ROH -NiCo2 O3 can achieve broad CO/H2 ratios from 0.51 to 1.24. This work offers in-depth insights into adjustable syngas photosynthesis and generalized concepts of selective heterogeneous CO2 photoreduction beyond cobalt-based oxides.