Controllable Synthesis of Vacancy-Defect Cu Site and Its Catalysis for the Manufacture of Vinyl Chloride Monomer

Designing favorable structures of active sites and clarifying the structure-activity relationship are important to narrow the large activity gap between Cu-based and the noble-metal-based catalytic systems for vinyl chloride production. Herein, we report a facile controllable thermal method for fabricating the platform of Cu single-atom catalysts ranging from the standard no-vacancy-defect CuCl3-N to vacancy-defect CuCl2V-N (V for the vacancy-defect site) and to no-vacancy-defect CuN4. The gradually released C-Cl derivatives promote the vacancy-defect generation under elevated temperatures, and the activity gap between Cu- and the noble-metal-based systems is found to be dramatically narrowed from classic similar to 37-fold to similar to 1.5-fold on the vacancy-defect sites. Kinetic analysis shows that the competitive adsorption between acetylene and hydrogen chloride on the CuCl2V-N site contributed more to the catalytic performance than the single hydrogen chloride adsorption on site CuCl3-N or CuN4. Furthermore, when the CuCl2V-N site is preoccupied and adsorbed by acetylene, the reaction energy barrier decreases from 35 to 24 kJ/mol, indicating that the single activation of acetylene is more favorable for catalytic activity than that of the dual-activation of acetylene and hydrogen chloride. DFT calculations revealed the specific reaction mechanism catalyzed on the vacancy-defect CuCl2V-N site, i.e., where the vacancy-defect not only affects the activation behavior of substrates but also regulates the reaction pathway. Excellent catalytic performance can be maintained under the interaction of high concentration of vinyl chloride and H2S impurity. This work opens a new window for controllable synthesis of vacancy-defect sites of single metallic atoms in catalysis design and enhancing catalytic activity.

Automated summary

The study focuses on designing favorable structures for active sites to narrow the gap in activity between Cu-based and noble-metal-based catalytic systems for vinyl chloride production. A method for fabricating Cu single-atom catalysts is reported, with gradual release of C-Cl derivatives promoting vacancy-defect generation and significantly reducing the activity gap. Competitive adsorption between acetylene and hydrogen chloride on the CuCl2V-N site was found to enhance catalytic performance, and DFT calculations revealed a specific reaction mechanism catalyzed on the vacancy-defect CuCl2V-N site.