Descriptors for High-Performance Nitrogen-Doped Carbon Catalysts in Acetylene Hydrochlorination

Nitrogen-doped carbons are promising materials for a broad range of applications. However, their rational design is greatly hampered by the lack of efficient methods to control the nitrogen speciation, which not only causes controversy about the roles of specific nitrogen functionalities but also hinders investigations into other physicochemical characteristics of these materials. We herein present a cutting-edge strategy that allows a systematic tuning of the electrical conductivity of polyaniline-derived N-doped carbons at a defined nitrogen speciation and content, and similar porous properties. By application of these model systems in acetylene hydrochlorination, a major industrial technology for the production of polyvinyl chloride, we provide insights into the active sites and the reaction mechanism and disclose two key catalytic descriptors for N-doped carbons in this reaction: (i) a high content of pyrrolic-N functionalities, promoting the adsorption of the reactants, and (ii) good electrical conductivity, likely influencing the surface diffusion of adsorbed species. Since increasing the electrical conductivity leads to a reduced nitrogen content, the interplay between these two properties must be carefully controlled to maximize catalytic performance. This understanding enabled the design of the first N-doped carbon catalyst that rivals the unprecedented activity of benchmark gold-based systems in acetylene hydrochlorination.