High steam utilization operation with high current density in solid oxide electrolysis cells

Abstract

Feasibility of high steam utilization operation with high current density in solid oxide electrolysis cells (SOECs) was investigated. Although higher reactant utilization leads to high efficiency and flexibility in SOEC systems, it increases the concentration polarization resistance, consequently decreasing the limiting current density, namely, decreasing the production rate of the energy carrier. To decrease the concentration polarization resistance, a porous structure-controlled NiO and Y 2 O 3 -stabilized ZrO 2 (YSZ) composite substrate prepared via an extrusion process was therefore used for a fuel electrode of an SOEC. After reduction of the fuel electrode, the porosity reached 54 vol.% and Ni, YSZ, and pores were uniformly distributed. In electrochemical measurements, the SOEC showed a high current density of 1.43 A cm ¹2 at the thermo-neutral voltage at 800°C using a mixture of 20% steam in hydrogen (feed rate for excess supply). At high steam utilization of 90% and a resulting partial pressure of residual water of 0.02 atm, the SOEC could operate even at a high current density of 1.25 A cm ¹2. The calculated concentration overpotential suggested that high steam utilization with high current density is feasible by using highly porous fuel electrodes.

Structural investigation of electrochemically active ceramic anodes for next-generation solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs)

“…An ideal gas permeation structure was achieved for high steam utilization. 9) The IV curve for the developed SOEC with a highly porous NiYSZ anode measured at 700800°C using 20% wet H 2 (at a feed rate of 100 standard temperature and pressure cm 3 /min, passed through a water bubbler) is shown in Fig. 10.…”

Preparation and Properties of PrBa0.5Sr0.5Co1.5Fe0.5O5+δas Novel Oxygen Electrode for Solid Oxide Electrolysis Cells

“…The traditional oxygen electrode is La 0.8 Sr 0.2 MnO 3-δ (LSM)-yttria stabilized zirconia (YSZ) (6,7), but it needs high temperatures to achieve good performance. Others alternative materials such as La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) (8)(9)(10)(11), La 0.8 Sr 0.2 Co 0.8 Ni 0.2 O 3-δ (LSCN) (12,13), and Ba 0.5 Sr 0.5 Co 0.2 Fe 0.8 O 3-δ (BSCF) (14) have also been investigated. Although these materials have been confirmed to give good performance as SOEC oxygen electrode, they still face a variety of problems such as the thermal expansion coefficient mismatch (15), low stability and insufficient catalytic performance (16).…”