High-Volumetric Density Atomic Cobalt on Multishell Zn x Cd 1- x S Boosts Photocatalytic CO 2 Reduction.

The volumetric density of the metal atomic site is decisive to the operating efficiency of the photosynthetic nanoreactor, yet its rational design and synthesis remain a grand challenge. Herein, we report a shell-regulating approach to enhance the volumetric density of Co atomic sites onto/into multishell Zn x Cd 1- x S for greatly improving CO 2 photoreduction activity. We first establish a quantitative relation between the number of shell layers, specific surface areas, and volumetric density of atomic sites on multishell Zn x Cd 1- x S and conclude a positive relation between photosynthetic performance and the number of shell layers. The triple-shell Zn x Cd 1- x S-Co 1 achieves the highest CO yield rate of 7629.7 μmol g -1 h -1 , superior to those of the double-shell Zn x Cd 1- x S-Co 1 (5882.2 μmol g -1 h -1 ) and single-shell Zn x Cd 1- x S-Co 1 (4724.2 μmol g -1 h -1 ). Density functional theory calculations suggest that high-density Co atomic sites can promote the mobility of photogenerated electrons and enhance the adsorption of Co(bpy) 3 2+ to increase CO 2 activation (CO 2 → CO 2 * → COOH* → CO* → CO) via the S-Co-bpy interaction, thereby enhancing the efficiency of photocatalytic CO 2 reduction.