Highly Active and Stable Pt₃Rh Nanoclusters as Supportless Electrocatalyst for Methanol Oxidation in Direct Methanol Fuel Cells

Abstract

The supportless PtRh nanoclusters (Pt3Rh NC) were prepared using formic acid reductant. High-resolution transmission electron microscopy (HRTEM) showed individual particle sizes less than 7 nm, and energy-dispersive X-ray (EDX) analysis confirmed a 3:1 ratio of Pt and Rh. The as-prepared Pt3Rh NC exhibited an improved activity and durability toward electrocatalytic oxidation of methanol (MOR) and possesses greater CO tolerance than conventional PtRu and other Pt-based MOR catalysts. For comparison, the Vulcan carbon supported (Pt3Rh NC/VC) catalyst was prepared under identical conditions and used for MOR. The supportless Pt3Rh NC catalyst possessed mass activity of 1392.5 mA mg–1 with an I f/I b ratio of 2.61, which is nearly 3-fold higher than the Pt3Rh NC/VC and also comparable to the benchmark MOR catalysts. The surface poisoning rate was found to be relatively smaller compared to the standard PtRu/C catalysts (δ = 0.0044% s–1). The activation energy for MOR was found to be 22.5 kJ mol–1. The durability study for 4000 potential cycles in an acidic solution showed that nearly 78% of mass activity has been retained. The supportless Pt3Rh NC has much improved activity and stability compared to both Pt3Rh NC/VC and standard PtRu MOR catalysts. Therefore, the supportless Pt3Rh NC could be seen as a potential electrocatalyst for methanol oxidation due to high activity, enhanced stability, and diminished poisoning of the Pt surface, which is stabilized in the presence of Rh in nanocluster morphology.

Mechanochemical Synthesis of Free‐Standing Platinum Nanosheets and Their Electrocatalytic Properties

“…Even though the sheets consist of nanocrystals without any predominant crystal facet, their freestanding nature should provide much higher electrochemically active surface area (ECSA) and better efficiency for the following reasons. (1) Usually catalyst nanocrystals are anchored onto conducting supports such as graphene, RGO or amorphous carbon in order to reduce their agglomeration and increase conductivity . Otherwise, the loosely bound nanocrystals within agglomerates behave as Schottky contacts leading to higher reaction overpotential.…”

Controlled Synthesis of Pt–Pd Nanoparticle Chains with High Electrocatalytic Activity Based on Insulin Amyloid Fibrils

“…0.64 V versus SCE) during the forward scan is usually ascribed to the oxidation of methanol to smaller short chain organic molecules and carbon monoxide. 22 It is clear that the forward peak current density for the samples is 0.62, 0.31, 0.29, 0.27 mA cm À2 (black, red, green and blue line), which is especially for the Pt-PdNPCs about two times higher than that for the commercial Pt/C catalyst, suggesting a higher MOR catalytic activity of Pt-PdNPCs. Furthermore, the ratio of peak currents associated with the anodic peaks in forward (I f Þ and reverse (I b Þ is generally used to assess the CO tolerance of the catalyst.…”

Research advances in unsupported Pt-based catalysts for electrochemical methanol oxidation

“…Foreign transition metals are often employed to form alloys with Pt nanostructures, and the integration of other metals can sharply increase the utilization efficiency of Pt atoms. More importantly, this strategy will considerately enhance its MOR activity by modulating the binding strength between Pt atoms and the adsorbed oxygen-containing carbon species due to the synergistic effects, that is, ensemble, ligand and strain effects [63][64][65][66][67] . Ensemble effects exist when various surface atoms represent different reaction mechanisms, as illustrated for ruthenium (Ru) atom combined Pt atoms for MOR.…”