Synergistic Modulation of Nitrogen Vacancies and SMSI Effects in Pd/g-C 3 N 4 for Low-Temperature Formaldehyde Oxidation

Creating vacancies and modulating the strong metal-support interaction (SMSI) are crucial strategies for enhancing catalytic activity in heterogeneous catalysis, widely explored for noble metals and oxide supports. In this work, these regulating strategies were extended to nonoxide supports. Specifically, CN supports were calcined at different temperatures to control N-vacancies, while the SMSI effect was tuned via varying the reduction temperature. Characterization and DFT calculations demonstrated that N-vacancies are capable of donating electrons to Pd nanoparticles, promoting the activation of O₂ and thus promoting catalytic performance. Nevertheless, SMSI overlayer forms during reduction and may inhibit activity once Pd is fully encapsulated. As the reduction temperature reaches 300 °C, partial de-encapsulation leaves a residual ultrathin layer. This defective SMSI layer resembles support defects, enhancing the electronic activity of the metal surface and further improving catalytic activity. By optimizing N-vacancies and SMSI, the Pd/CN650 catalyst reduced at 300 °C exhibited excellent HCHO oxidation performance at room temperature, highlighting the potential of nonoxide supports for sustainable catalysis.