An Up-scalable, Infiltration-Based Approach for Improving the Durability of Ni/YSZ Electrodes for Solid Oxide Cells

Abstract

In solid oxide electrolysis cells (SOECs), considerable degradation of the Ni/YSZ electrode during long-term electrolysis operation at high current densities (−1 A cm -2 or above) has been an ongoing challenge. In this work we report on a method alleviating the problem based on infiltrating nano-sized electrocatalysts into the Ni/YSZ electrode of a full cell after it has been reduced in a "one-atmosphere-reduction" process. The performance and durability of infiltrated and non-infiltrated cells are evaluated at full test-cell size of 4 x 4 cm 2 level. The infiltrated cell exhibits significantly enhanced durability when operated for steam electrolysis at 750 °C under high current densities, with cell voltage degradation rates of 0.028 V kh -1 (2.0 % kh -1 ) for 800 h at −1.25 A cm -2 and 0.010 V kh -1 (0.8 % kh -1 ) for 300 h at −1.00 A cm -2 . These degradation rates are ∼14 times and ∼25 times smaller than those of the non-infiltrated cell, respectively.The infiltrated cell also shows superior durability to the non-infiltrated cell during reversible operation. These results demonstrate the great potential of boosting the durability of state-of-

Recent advances in solid oxide cell technology for electrolysis

“…infiltration, atomic layer deposition (ALD), pulsed layer deposition (PLD), exsolution etc. (40)(41)(42)(43). Applying infiltrated nano-sized electro-catalysts into a Ni-YSZ electrode structure shrinks the catalytic particles from micro-meter scale to the nano-meter scale, and dramatically increases TPB lengths, thereby enhancing electrode performance.…”

“…Compared to a standard electrode, electrodes with increased number of active sites per electrode volume will inevitably be able to operate at lower overpotential for the same given externally set current density. Furthermore, nano-particle infiltrated Ni-YSZ electrodes have shown to be stable for hundreds of hours at high current densities (40).…”

Short-Term Strong Cathodic Polarization of Ni/YSZ and Pt/YSZ

“…10 The inductive low frequency arc has not only been observed for simple point contact electrodes, but also on larger porous SOEC Ni electrodes, where it has been attributed to a competition between blocking Si impurities from glass cell packings and water adsorption, 12 introduction of electronic conductivity in the YSZ phase 13 and reduction of YSZ. 14 For polarizations from −1.3 V and down, the spectra in Fig. 9 show an indication of a capacitive arc at frequencies above the range used.…”

“…10 In very recent SOEC degradation studies with rather large active electrode areas, inductive low frequency loops were observed and attributed to an adsorption process that allows H 2 O reduction on Ni sites polluted with Si impurities from the sealing, 12 electronic conduction through the YSZ electrolyte 13 or reduction of YSZ. 14 Except for the RCT works mentioned above, most studies of Ni-YSZ reactions have been carried out in a timescale of days. In the present work, the focus is on the initial stages of the Ni|YSZ reduction ranging from minutes to a few hours.…”

Promotion of oxygen reduction and evolution by applying a nanoengineered hybrid catalyst on cobalt free electrodes for solid oxide cells

“…29,45,46,54,55 We have found that surface modification of the Ni/YSZ electrode by coating nano-sized Ce0.8Gd0.2O2-δ (CGO20) electrocatalysts is an effective approach to enhance the cell durability. 29,45,56 Here, we applied this approach to the hybrid-catalyst-coated LSF cell thus resulting in a double-side modified cell (with a CGO20coated Ni/YSZ fuel electrode and the hybrid-catalyst-coated LSF oxygen electrode). At 1.3 V, the current densities of the such cell are 1.86, 1.41, 0.82 A cm −2 at 750, 700, and 650 °C, respectively (Fig.…”