A Strategy for Drastic Improvement in the Durability of Pt/C and PtCo/C Alloy Catalysts for the Oxygen Reduction Reaction by Melamine Surface Modification

Abstract

A strategy for drastic improvement in the durability of a Pt/C catalyst and a PtCo/C alloy catalyst for the oxygen reduction reaction (ORR) by melamine surface modification was demonstrated. The durability of the catalysts was evaluated by an accelerated durability test (ADT) using a square wave potential cycling of 0.6–1.0 V vs RHE performed in Ar-saturated 0.1 mol dm–3 HClO4 containing a very small amount of melamine (10 μmol dm–3) at 80 °C for 10,000 cycles. Transmission electron microscopy (TEM) observations showed that melamine addition suppressed a size increase in the catalyst nanoparticles (NPs) during the ADT caused by the Ostwald ripening and/or migration-coalescence, which mitigated a loss in the electrochemical surface area of the catalysts. More importantly, TEM-EDX compositional analysis revealed that melamine addition suppressed Co dealloying of the PtCo NPs during the ADT and the alloy catalyst retained a high ORR mass activity of 1019 A g–1-Pt at 0.9 V vs RHE even after the ADT. The durability improvement is considered to arise from the suppression of Pt-oxygenated species formation caused by destabilization of a stable water molecule network formed on the catalyst surface and selective adsorption of melamine molecules at low-coordination surface Pt sites. Our results open up an alternative avenue for drastic improvement in the durability of the Pt-based catalysts for the ORR in polymer electrolyte fuel cells.

Role of Transition Metals in Pt Alloy Catalysts for the Oxygen Reduction Reaction

“…Surface modifiers and ionic liquids present an interesting new avenue of research in electrocatalysis . Several groups have explored the use of organic molecules to decorate the Pt surface and tune specific interactions. − Cherevko et al applied the ICP-MS with scanning flow cell technique to trimetallic PtNiMo/C modified with ionic liquids. , Previous work has shown positive effects of ionic liquid modification on single-element Pt catalysts, but the effect on multimetallic catalysts is less clear. ,, The dissolution profiles of each of the metals were studied by SFC-ICP-MS. In this case, the ionic liquid promotes leaching of the Mo from the catalyst surface, eliminating the stabilizing effect on nickel.…”

Cu–Co bimetallic nanocluster Mott–Schottky interaction increasing oxygen reduction reaction activity in rechargeable Zn-air batteries

“…OH*, O* and OOH*), multiple adsorption/ desorption steps and complex multi-electron transfer processes of the products contribute together to the slow ORR and OER kinetics. 10,11 Although platinum group metal (PGM)-based catalysts such as RuO 2 /IrO 2 still perform well in ORR and OER processes, 12,13 their high costs severely limit their large-scale application possibilities in rechargeable ZABs. 14,15 Therefore, it is imperative to design and develop non-PGM electrocatalysts with bifunctional catalytic activity and high durability.…”

Elucidation of the mechanism of melamine adsorption on Pt(111) surface via density functional theory calculations

“…Moreover, melamine significantly enhanced the durability of the Pt catalyst against rapid deterioration at 80 1C. 31,32 Notably, melamine is a low-cost, massproduced compound, with potential for practical applications.…”