3D-printed flow-mode atmospheric pressure glow discharge reactor for the synthesis of multi-metallic Pt-/ Pd-/ Os-/ Ru-/ Re-/ W-/ Cr-/ nanocluster catalysts

Abstract

In this study, cold atmospheric pressure plasma (CAPP) was used to synthesise "electron-rich" multi-metallic nanocluster catalysts (NCs) from precursors containing Pt, Pd, Os, Ru, Re, W and Cr, with potential applications in hydrogenation reactions. To this end, direct-current atmospheric pressure glow discharge (dc-APGD) was operated in two configurations: a flowing liquid anode (FLA) and a flowing liquid cathode (FLC). The CAPP system was fabricated using stereolithography.The NCs were characterised by dynamic light scattering and electrophoretic light scattering. Catalytic activity was evaluated using the reduction of 4-nitrophenol (4-NP) to 4-aminophenol. Morphology and surface composition were examined by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The NCs were predominantly smaller than 1 nm forming clustered atoms. The NCs synthesised by FLA-and FLC-dc-APGD with ruthenium as the dominant metal and tungsten as the secondary metal (Ru W NCs) exhibited zeta potentials of 32.58 ± 0.16 mV and 32.42 ± 0.46 mV, respectively, indicating good colloidal stability. Ru W NCs synthesised by FLA-and FLC-dc-APGD also showed the highest 4-NP reduction activity, with mass-normalised rate constants (k1m b ) of 17.81 min -1 mg -1 and 18.09 min -1 mg -1 (75% and 81% conversion), respectively. OsPd/CrNCs synthesised by FLA-dc-APGD demonstrated comparable catalytic performance (k1m b = 15.87 min -1 mg -1 ), achieving 86% 4-NP conversion. Notably, this conversion was attained within 1.2 min, whereas all reported values correspond to a reaction time of 8 min.