Effect of PdNiBi Metal Content: Cost Reduction in Alkaline Direct Ethanol Fuel Cells

Abstract

In this work, the metal content of Pd85Ni10Bi5/C catalysts for the alkaline ethanol-oxidation reaction was reduced from 40 wt.% (PdNiBi/C (40/60)) to 30 wt.% (PdNiBi/C (30/70)), 20 wt.% (PdNiBi/C (20/80)) and 10 wt.% (PdNiBi/C (10/90)), while increasing performance. The synthesized catalysts were examined using physicochemical measurements and electrochemical measurements. The best performing catalysts were used to fabricate membrane electrode assemblies for carrying out single-cell tests and to determine the influence of the metal/carbon ratio of the electrode. The electrochemical surface area (695 cm2 mg−1) and activity were increased, resulting in high peak-current densities for the ethanol oxidation reaction (3.72 A mg−1) by the resulting more accessible metal particles. The electrode produced with the PdNiBi/C (30/70) catalyst reached a maximum power density of 34.8 mW mg−1 at 50 °C. This successfully demonstrated a doubling of the power density compared with the performance of the PdNiBi/C (40/60) electrode, while simultaneously reducing the costs.

Influence of the electrocatalyst layer thickness on alkaline DEFC performance

“…Based on these half-cell GDE measurements, the previously described advantage over RDE measurements is clearly visible. The CVs are in a similar current range as the RDE measurements from the literature, 12,18 but higher currents for the ORR can be achieved than with the RDE. Through the use of the gas diffusion layer and the continuous supply of the reactants, the conditions of the fuel cell can be better simulated.…”

“…The Pd 85 Ni 10 Bi 5 /C anode catalyst (30 wt% active material) was synthesized as described in the previously published literature. 18 As no modifications were made to the synthesis of the catalyst, the synthesis itself is shown here in a very simplified form. Vulcan XC72R is dispersed in ultrapure water and then the three metal salt precursor solutions (PdCl 2 , Ni(NO 3 ) 2 ·6H 2 O and BiCl 3 in water and HCl) are added.…”

“…2,13 Ni or Bi, for example, which are oxophilic elements, contribute to the improvement by facilitating the oxidation process and the oxidative removal of poisonous intermediate species. [16][17][18] Since the catalysts are not capable of completely converting ethanol, the alkaline DEFC is currently operated as a liquid-feed cell, which means that KOH is added to the fuel mixture on the anode side (more OH − available). The use of a liquid electrolyte in addition to a membrane involves disadvantages such as carbonation.…”

Reduced graphene oxide as efficient carbon support for Pd-based ethanol oxidation catalysts in alkaline media

“…The peaks at 2 values of 39.7 and 43.9° indexed to the (111) and (200) facets, respectively, can be assigned to the face-centered cubic crystalline structure of Pd [8,11]. The shift to lower angles is caused by lattice expansion due to nanosized particles and alloying with Ni and Bi [7,13,15]. The nanocrystalline nature is further indicated by the broad peak shape.…”

“…The PdNiBi/rGO (40 wt.% of metal and 60 wt.% of carbon support) composite catalyst was synthesized according to the modified instant reduction method [7,15]. The as-prepared rGO was dispersed in ultrapure water under a nitrogen atmosphere and ice cooling using an ultrasonic probe (Hilscher, UP440s).…”