PdAg Nanorings Supported on Graphene Nanosheets: Highly Methanol‐Tolerant Cathode Electrocatalyst for Alkaline Fuel Cells

Abstract

Due to the high costs, slow reaction kinetics, and methanol poisoning of platinum‐based cathode catalysts, designing and exploring non‐Pt or low‐Pt cathode electrocatalysts with a low cost, high catalytic performance, and high methanol‐tolerance are crucial for the commercialization of fuel cells. Here, a facile method to fabricate a system of PdAg nanorings supported by graphene nanosheets is demonstrated; the fabrication is based on the galvanic displacement reaction between pre‐synthesized Ag nanoparticles and palladium ions. X‐ray diffraction and high‐resolution transmission electron microscopy show that the synthesized PdAg nanocrystals exhibit a ring‐shaped hollow structure with an average size of 27.49 nm and a wall thickness of 5.5 nm. Compared to the commercial Pd–C catalyst, the PdAg nanorings exhibit superior properties as a cathode electrocatalyst for oxygen reduction. Based on structural and electrochemical studies, these advantageous properties include efficient usage of noble metals and a high surface area because of the effective utilization of both the exterior and interior surfaces, high electrocatalytic performance for oxygen reduction from the synergistic effect of the alloyed PdAg crystalline phase, and most importantly, excellent tolerance of methanol crossover at high concentrations. It is anticipated that this synthesis of graphene‐based PdAg nanorings will open up a new avenue for designing advanced electrocatalysts that are low in cost and that exhibit high catalytic performance for alkaline fuel cells.

PdNi Hollow Nanoparticles for Improved Electrocatalytic Oxygen Reduction in Alkaline Environments

“…7,[11][12][13][14] Pd alloyed with transition metals (Pd-TMs), such as Pd-Ni, [15][16] Pd-Cu, [17][18][19][20] 27 while the ORR performance was not improved, mainly because the larger lattice constant of silver would subject the Pd to a tensile strain effect, decreasing the electroactivity of Pd towards the ORR. 36 Pd-Co 37 and Pd-Cu 38 hollow nanostructures were also reported with large particle size (> 50 nm) but their ORR properties were not extensively studied due to the large particle size, which may decrease the active surface area.…”

Graphene‐Supported Metal Nanostructures with Controllable Size and Shape as Advanced Electrocatalysts for Fuel Cells

“…The electrocatalysts in fuel cells are generally considered to determine the cost and the overall performance of the cells [38]. As described above, although Pt-based nanomaterials are the most active electrocatalysts for both anode and cathode reaction processes in fuel cells, the application of pure Pt catalysts are limited by its high cost, limited occurrence in nature, poor durability, and the easy self-poisoning by the carbon monoxide intermediate produced in electrode reactions.…”

Electroreduction of Nitroaromatic Compounds at Electrochemically Reduced Graphene Oxide Supported Bimetallic Ag@Pd Nanorods Modified Electrodes

“…The synthesis of Ag@Pd nanostructures on the reduced graphene oxide surface was reported elsewhere by different techniques such as successive reduction, hydrothermal and co-reduction of two different metal ions [24][25][26]. In the successive generation of thin layer of shell like second metal on base metal, the galvanic replacement method has been considered as the most effective, simple and a versatile tool due to the use of extremely low loading of noble metals [27,28]. On the other hand, the bimetallic nanostructures of noble metals such as Pt or Pd with Ag have not been studied extensively due to two reasons: (1) the generated Ag + ions in the replacement process do readily react with the halide ions in the aqueous solution of noble metals to form waterÀinsoluble silver halides or (2) the other waterÀsoluble noble metal precursor such as cyanides or amines are less reactive than halides [29].…”