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.