Enhanced Catalysis of Pt_(3) Clusters Supported on Graphene for N–H Bond Dissociation

We report an in-depth study of catalytic N–H bond dissociation with typical platinum clusters on gra-phene supports.Among all the pristine graphene-and defective graphene-supported Pt clusters of different sizes that were studied,the Pt_(3)/G cluster possesses the highest reactivity and lowest activa-tion barriers for each step of N–H dissociation in the decomposition of ammonia.

Interfacial charge effects of supported-metal-cluster heterostructures on azo hydrogenation catalyzation

The impact of interfacial charge on catalytic performance of supported-metal-cluster(SMC)heterostructures remains unclear,hindering efforts to develop high-performance SMC catalysts.Herein we systematically investigated interfacial charge effects of SMCs using a model system of graphene-supported gold-nanoclusters(AuNCs/rGO)for azo hydrogenation.Three types of SMCs with different interfacial charges were synthesized by anchoring electropositive 2-aminoethanethiol(CSH),amphoteric cysteine(Cys),and electronegative 3-mercaptopropionic-acid(MPA)onto AuNCs/rGO,respectively.All three SMCs exhibited high and selective catalytic activity to azo-hydrogenation in four representative azo dyes.The catalytic activity of Cys@AuNCs/rGO was lower than that of CSH@AuNCs/rGO but higher than that of MPA@AuNCs/rGO.However,the cyclic stability of Cys@AuNCs/rGO was inferior to that of both CSH@AuNCs/rGO and MPA@AuNCs/rGO.Further mechanistic studies revealed that amino ligands modified CSH@AuNCs and Cys@AuNCs agglomerated into large-size gold nanoparticles on rGO surface during catalytic reaction under NaBH_(4) action,leading to reduced efficiency and cyclic stability.Conversely,non-amino ligand modified MPA@AuNCs only partially detached from rGO surface without agglomeration,resulting in better cyclic stability.Protection of amino groups in ligands such as modifying-NH_(3)^(+)group in Cys into imine to form N-isobutyryl-L-cysteine(NIBC)substantially improved the cyclic stability while maintaining the high activity in the NIBC@AuNCs/rGO catalyst system.Our work provides an approach for developing a highly-active and stable SMC heterostructure catalyst via manipulating interfacial charges in SMC.