Research and Perspectives on Surface Functional Group Characterization of Activated Carbon Catalysts

Activated carbon is a commonly used catalyst and catalyst support. Its abundant surface groups play a key role in catalytic activity and selectivity, and therefore an in-depth investigation of the surface groups of activated carbon is of great significance. The surface groups of activated carbon are diverse and structurally complex, and the corresponding characterization methods are also varied, with each technique having its own advantages and limitations. This review systematically summarizes the sources, characteristics, and effects on catalytic processes of oxygen-containing, nitrogen-containing, phosphorus-containing, and other heteroatom-containing groups on activated carbon surfaces. Emphasis is placed on the application of Boehm titration, PZC/IEP, FT-IR, XPS, TPD-MS, Raman, XRD, solid-state NMR, SEM/EDS, and EPR/ESR in the study of surface groups on activated carbon. Because the formation and alteration of surface groups on activated carbon not only change the surface chemical properties of activated carbon but also affect its structure, charge, and related properties, a single characterization method cannot accurately and comprehensively reveal its characteristics. Therefore, in practical studies, multiple characterization methods should be combined for cross-validation from the perspectives of functional group type, chemical state, thermal stability, structural changes, and catalytic behavior, so as to establish reliable correlations among “group type–structural environment–catalytic performance” and provide a basis for the rational design and optimization of activated carbon catalysts.