Controlling nanostructures of PtNiCo/C trimetallic nanocatalysts and relationship of structure-catalytic performance for selective hydrogenation of nitroarenes

Abstract

Herein, we report a simple synthesis of PtNiCo trimetallic nanoparticles (NPs) loaded on carbon black (PtNiCo/C) via ambient-temperature chemical reduction and galvanic replacement reaction. The influence of thermal treatment temperature in 10 %H2/N2 on PtNiCo NPs in PtNiCo/C-X nanostructures is revealed, where, X = 200 °C, 500 °C. XRD, XPS, TEM, HAADF-STEM, HRTEM, STEM-EDX elemental line-scanning (mapping), HS-LEIS, H2-TPR, atomic resolution aberration-corrected STEM (AC-STEM), XANES and EXAFS have been employed to characterize various nanostructures of PtNiCo NPs in PtNiCo/C-X. We established the relationship of nanostructure-reducing temperature thus catalytic behavior of PtNiCo/C-X: PtNiCo/C-200 ∼ Pt island (single atom and cluster)-on-NiCo alloy NP, PtNiCo/C-500 ∼ PtNiCo alloy NPs. PtNiCo/C-200 provides much improved catalytic activity and selectivity to target products (NO2 group hydrogenation) as compared to PtNiCo/C-500 for nitroarenes selective hydrogenation under mild reaction conditions (1.0 MPa-H2 pressure, 18 °C or 40 °C-reaction temperature). That is considered to be closely correlated with the synergy effect of Pt islands and NiCo alloy nanoparticles in PtNiCo/C-200.