Pd/Ni Synergestic Activity for Hydrogen Oxidation Reaction in Alkaline Conditions

Abstract

The investigation of hydrogen oxidation reaction (HOR) in alkaline conditions has been the subject of a wide interest in the past few years with the rise of alkaline membrane fuel cells (AMFCs). In particular, the quest for the lowest content of platinum group metals (PGMs) in the HOR catalyst is ongoing. In this article, we propose the use of a nanoscale Pd layer partially covering a Ni film to provide the most efficient use of the PGM in the HOR catalyst. The Pd/Ni electrodes were prepared by spontaneous and electrolytic deposition of Pd onto smooth polycrystalline Ni surfaces with different surface compositions. The electrodes were characterized by cyclic voltammetry and atomic force microscopy. Electrocatalytic activity in HOR of the Pd/Ni electrodes was measured in alkaline solution by rotating disc electrode method. In the manuscript, we demonstrate that a Pd coverage as low as 1.5% vs. Ni coverage is sufficient to provide a high current density compared to pure Ni. The current density linearly increases with the Pd coverage up to a Pd coverage of 17%; upon further increase in the Pd coverage, the current density reaches a plateau, i.e. the diffusion limit for the HOR process.The comparison with Pd supported on carbon shows the clear benefit for the bimetallic catalyst.

What Can We Learn in Electrocatalysis, from Nanoparticulated Precious and/or Non-Precious Catalytic Centers Interacting with Their Support?

“…This value < 0.1mA/cm 2 Pd is the usual value for palladium in alkaline medium, this was corroborated in a similar study where a gold surface was covered by palladium [142]. Coming back to the Pd/Ni study, the highest exchange current values were obtained with a low Pd coverage, even above 1.5% on Ni (Figure 21 (red dots)) [140].…”

“…It was also determined that Pd/C catalysts, under the same work conditions conveyed values below 0.1 mA/cm 2 Pd at an overvoltage η = 0.05 V with a palladium loading of 5 μg/cm 2 [141], while Pd/Ni with 0.9 μg/cm 2 reaches 0.30 mA/cm 2 disc and 0.57 mA/cm 2 Pd at an overvoltage η = 0.05 V [120]. For Ni covered by a high amount of Pd, the exchange current density Recent papers have proposed the use of various nanoscale electrocatalysts, such as Ni films partially covered by a palladium layer which provide one of the most active materials for the HOR [140]. These Pd/Ni electrodes were synthesized by an electrolytic deposition of palladium over a polycrystalline Ni surface varying the composition of the surface.…”

“…Both parameters did not present further improvement with a Pd deposition above 17%, Figure 21. Recent papers have proposed the use of various nanoscale electrocatalysts, such as Ni films partially covered by a palladium layer which provide one of the most active materials for the HOR [140]. These Pd/Ni electrodes were synthesized by an electrolytic deposition of palladium over a polycrystalline Ni surface varying the composition of the surface.…”

Effect of Co‐catalyst on the Selective Electrooxidation of Glycerol over Ruthenium‐based Nanomaterials

“…Several studies in alkaline media have demonstrated that Pd is am ore effective catalystt han Pt. [21][22][23][24] Although Pd is also an oble and expensive metal,i ti sh alf the price of Pt and its combination with another co-catalyst may substantially improve its efficiency in ar eactiona nd reduce the costs of electrode materials. [25][26][27][28][29][30] In fact, PtRu and PdRu catalysts with controlled particle sizes weres hown to provide significantly improved catalytic performances toward some organic fuels.…”

Unexpected Behavior of the Hydrogen Oxidation Reaction on Palladium in Alkaline Solution: A Feasible Kinetic Explanation

“…9 Therefore, the presence of H ab influences the kinetics of the hydrogen electrode reaction in their both directions, the cathodic hydrogen evolution reaction (her) and the hor, although it was not considered in most of the studies, where slow potentiodynamic sweeps were used. [10][11][12][13][14][15] Otherwise a work carried out on steady state in acid solutions, employing chronoamperometry, showed that the her is verified on βPd-H, while the hor involves both phases. 16 βPd-H is stable at low (η<0.05 V) and αPd-H at high overpotentials, being βPd-H better electrocatalyst.…”