A unique approach to designing resilient bi-functional nano-electrocatalysts based on ultrafine bimetallic nanoparticles dispersed in carbon nanospheres

Abstract

Activity and stability are the key issues for any catalyst. Importantly, the synthesis of catalysts should be facile. Here, we report one-step facile electroless synthesis of ultrafine bimetallic PdPt nanoparticles (∼2 nm) dispersed in hetero-atom doped hollow carbon nanospheres (HCNSs) and PdPt nanoparticles in carbon nanostructures (CNSs) as highly active and stable electrocatalysts for electro-oxidation/-reduction of low molecular weight alcohols such as methanol and ethanol/of oxygen. HCNSs inhibit some of the electrochemical degradation pathways such as migration, agglomeration, isolation and detachment of nanoparticles. The superior mass activity of ultrafine PdPt nanoparticles for methanol/ethanol electro-oxidation (12-/8-fold), excellent operational stability, and high J_f/J_b ratio over commercially available state-of-the-art Pt–C (20 wt%) make them a potential fuel cell anode catalyst. The activity is further improved when PdPt-HCNS and PdPt-CNS are taken together suggesting a synergistic effect. Further, oxygen reduction reaction (ORR) study with embedded nanostructures exhibits a positive ORR peak potential, positive on-set potential (ΔE_on-set ∼ −50 mV) & half-wave potential (ΔE_1/2 ∼ −25 mV), low Tafel slope (53 mV dec⁻¹), enhanced current density and superior stability compared to that of Pt–C along with preferential 4e⁻ ORR pathways. Overall, the catalyst reported here is a potential anode and cathode catalyst for direct alcohol alkaline as well as hydrogen fuel cells.