Cooperative Pd@CoNi/rG catalyst for highly efficient and stable electrocatalytic methanol and ethanol oxidations

Abstract

<p>Methanol and ethanol are liquid carriers of hydrogen, convenient and safe to store and transport, particularly of interest as mobile and marine fuels. These can be directly fed into a fuel cell to impart clean energy efficiently, only if their conversion can be cost-effectively catalyzed. In this regard, a cooperative catalyst is developed with atomic Pd species, in the form of single atoms and nanoclusters, dispersed over non-noble bi-metallic CoNi alloy nanoparticles, further supported on reduced graphene oxide (rG) (Pd@CoNi/rG). The catalyst demonstrates a methanol (ethanol) oxidation, MOR (EOR), mass activity (MA) of 1.730 (3.917) A mg⁻¹_{Pd (or Pt)}, 4.55 (60.26) times greater than that of the commercial 20 wt% Pt/C and 8.65 (20.61) times higher than that of the commercial 20 wt% Pd/C, respectively. More importantly, the catalyst shows excellent stability, maintaining 83.7% (93.7%) of the initial performance after chronoamperometry (CA) for 50000 s in a solution of 1 M KOH + 1 M CH₃OH (CH₃CH₂OH). It significantly out-performs other mono-/bi- metallic counterparts, e.g., Co/rG, Ni/rG, Pd/rG, CoNi/rG, Pd@Co/rG and Pd@Ni/rG, due to its unique cooperative nanostructure with synergistic effects of the different metal (Pd, Co and Ni)-related species.</p>