Density Functional Theory Study of the Immobilization and Hindered Surface Migration of Pd₃ and Pd₄ Nanoclusters over Defect-Ridden Graphene: Implications for Heterogeneous Catalysis

Graphene nanosheets have been considered as robust support materials for metal nanoparticles and clusters with prominent applications to heterogeneous catalysis. In this study, by using the density functional theory, we performed a systematic investigation of the binding energetics, electronic charge analysis, and migratory surface barriers of free and solvated Pd3 and Pd4 clusters over pristine and defect-ridden graphene. Intrinsic as well as extrinsic defects were considered. In intrinsic defects, Stone–Wales defect, single-vacancy defect, and double-vacancy defect were considered, while in extrinsic defects, boron-, nitrogen-, and oxygen-doped systems were considered. Our investigation highlighted double-vacancy-defected graphene and B-doped graphene as excellent materials providing strong traps for Pd3 and Pd4 clusters, which not only immobilized the Pd clusters on them but also hindered their surface migration, thereby making them potential candidates for heterogeneous catalytic applications. With a particular reference to the prevalent application of Pd–graphene systems to the catalysis of hydrogenation reactions, we also studied the stability of the clusters in the presence of H2. Our calculations showed that the stability of the clusters was retained in the presence of H2, making them suited for the catalysis of hydrogenation reactions.