Steering Catalytic Activity and Selectivity of CO Photoreduction to Syngas with Hydroxy-Rich Cu S@R -NiCo O Double-Shelled Nanoboxes.

Simultaneous transformation of CO and H O into syngas (CO and H ) 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 Cu S (Cu S@R -NiCo O ), is prepared via a multistep templating strategy. The high performance of Cu S@R -NiCo O (7.1 mmol g  h for CO; 2.8 mmol g  h for H ) 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 R -NiCo O surface enhances *CO adsorption and lowers energy barriers for CO -to-CO. Therefore, modulating the hydroxy contents of R -NiCo O can achieve broad CO/H ratios from 0.51 to 1.24. This work offers in-depth insights into adjustable syngas photosynthesis and generalized concepts of selective heterogeneous CO photoreduction beyond cobalt-based oxides.