CoO engineered Co9S8 catalyst for CO2 photoreduction with accelerated electron transfer endowed by the built-in electric field

Fabricating highly active surface and rapid electron-transfer interface is an appealing route to develop an efficient catalyst to realize visible light driven photocatalytic CO2 reduction into value-added chemicals. Herein, we successfully synthesized the epitaxy of Co9S8 material with tiny CoO by using assembly-calcination method through controlling the amount of added thioacetamide as sulfur resource. As CoO is strongly anchored on the Co9S8, the bonding interaction between Co9S8 and CoO leads to the lattice distortion inside the material, attributing to the Jahn-Teller effect. The as-formed heterojunction between Co9S8 and CoO can create the built-in electric field, which drives the electron transfer from CoO to the Co sites of Co9S8 through the Co-O and Co-S covalent bonds. The existence of CoO also enhances the adsorption affinity of CO2 on the Co9S8 surface, as well as expands the bond length of C = O, which triggers the activation of CO2 molecule on the catalyst surface. While using [Ru(bpy)3]Cl2 (bpy: 2,2 '-bipyridine) as photosensitizer and triethanolamine as sacrificial agent, Co9S8/CoO@C displays excellent photocatalytic performance to realize the CO2 reduction to syngas. And the evolution rate of CO and H2 is 1.71 x 104 and 4.75 x 103 mu mol h-1 g-1 respectively. The DFT calculations demonstrate that the Co9S8/CoO heterojunction obviously reduces the kinetic barrier for the formation of intermediates during the photochemical reduction of CO2.

Automated summary

The epitaxy of Co9S8 material with tiny CoO formed a heterojunction, enhancing the efficiency of photocatalytic CO2 reduction. This heterojunction creates a built-in electric field, facilitating electron transfer and activation of CO2 molecules on the catalyst surface. DFT calculations confirm that the Co9S8/CoO heterojunction significantly reduces the kinetic barrier for intermediates formation during CO2 reduction.