Poly(amidoamine) dendrimer-protected Pt nanoparticles as a catalyst with ultra-low Pt loading for PEM water electrolysis

Abstract

Carbon-supported Pt-based electrocatalysts have been widely used on the cathode in proton-exchange membrane water electrolyser (PEM WE) for efficient H2 production. Graphitized carbon supports provide high electrical conductivity to catalyst layer and immobilize Pt nanoparticles (NPs), delivering high current densities (1 to 3 A cm−2) with durability during operation under acidic environment. However, use of Pt loadings as high as ∼20 and ∼40 wt.% in carbon support are detrimental for large-scale H2 production. In this work, PEM water electrolysis was performed using a single-cell assembly, constructed using carbon-supported dendrimer-encapsulated Pt nanoparticles (Dend-PtNPs) as the cathode and Ir black as the anode. Main aim of this study was to prepare/encapsulate Pt NPs within the dendrimer (Dend) with different surface groups (COONa, -NH2, -OH) and various generations (G3-G6). This was done in order to target ultralow Pt loadings (1 to 2 wt% on carbon) and anchor the resulting Dend-PtNPs onto highly conductive multi-layered graphene (MLG) support using 1-ethyl-3-(3-dimethylamino propyl) carbodiimide (EDC) and N‑hydroxyl sulfoxuccinimide (NHS) as the cross-linking agents for efficient H2 evolution reaction (HER). The amount of cross-linking agents used for the synthesis of Dend-PtNPs were optimised to achieve optimal HER performance. The mass loading of Pt on MLG support was determined using ICP-OES spectrometry. The MLG/Dend-PtNPs prepared by carboxylate (COONa) surface groups showed the excellent HER performance at zero potential and smaller Tafel slope value of 35 mV dec−1. The PEM WE performance of commercial catalyst (40% Pt on C) was compared with as prepared MLG/Dend-PtNPs catalyst with 1 to 2 wt.% Pt loading.