NiO/YSZ–YSZ Nanocomposite Functional Layer for High Performance Solid Oxide Fuel Cell Anodes

Abstract

The effect of inserting an anode functional layer (AFL) of NiO/yttria-stabilized zirconia (YSZ)–YSZ between the NiO–YSZ anode and the YSZ electrolyte on the performance of solid oxide fuel cells has been examined. Dual NiO/YSZ–YSZ composite powders synthesized by the polymerizable complex method result in composite nanosized NiO and YSZ particles adhered to core YSZ particles, and their mean particle size and surface area are 0.4μm and 39.0normalm2normalg−1 , respectively. The AFL is fabricated by dip-coating the anode substrate into a slurry of composite powders, and its thickness can be controlled by varying the withdrawn speed, while the composite-anode-supported YSZ electrolyte is also prepared by dip-coating the composite anode into the YSZ slurry, followed by sintering at 1400°C . It is concluded that the composite AFL is capable of minimizing the possibility of defect occurrence between anode and electrolyte layers during processing as well as considerably increasing the interface of the three-phase boundary. A unit cell with a 15μm thick AFL in conjunction with the LSM–YSZ cathode shows a maximum power density of 1.58Wcm−2 at 800°C in hydrogen (3% normalH2O ), which is about three times higher than that of the unit cell without the AFL.

Modeling Analysis of Bi-Layer Ni-(ZrO2)x(Y2O3)1−x Anodes for Anode-Supported Intermediate Temperature-Solid Oxide Fuel Cells

“…Actually, in this case, the slight increase of diffusion limitations by increasing the AL thickness, demonstrated in Figure 6c, becomes more effective. Further, some other literature works [18,56] report for 1/R p an increase up to AL thicknesses in the order of 15 µm, followed by a decrease. This is consistent with experimental literature data for single-layer HT-SOFC electrodes [57], and is captured, in our simulations, by the results in Figure 5, curves with ϕ el,AL = 0.34 (Case 2 b ), which show a maximum for an AL thicknesses in the order of 15 µm.…”

“…Depending on the morphology and thickness of the various layers, V-I curves, collected from complete IT-SOFCs in case where the anode is a main source of loss, can display a visible departure from linearity, with upward concavity (typical of activation effects and more visible at low operating current densities) [18,52], or downward concavity (typical of diffusion limitation effects and more visible at high operating current densities) [9]. In some cases, the V-I characteristic curves are very similar to those of low-temperature fuel cells, with a low-current density region with upward concavity related to activation losses, a linear intermediate region dominated by ohmic losses, and a high-current density region with downward concavity related to diffusive losses [53,54].…”

“…In order to conciliate mechanical and electrochemical needs, multi-layer electrodes have been proposed, consisting of two (or even more) different homogeneous layers. The anode is, thus, divided into a thick (between 0.5 mm and 1.5 mm) highly porous support layer (SL), enabling fast gas and electron transport, and, close to the electrolyte, a thin (5-20 µm) active layer (AL) devoted to the electrochemical reaction, with a finer microstructure in order to increase the TPB [17][18][19].…”

“…Table 1. Typical features of bi-layer anodes [9][10][11][17][18][19][22][23][24]. SL: support layer; and AL: active layer.…”

Single-step Preparation of Nano-homogeneous NiO/YSZ Composite Anode for Solid Oxide Fuel Cells

“…A fine anode structure with a uniform arrangement of Ni, YSZ (yttria-stabilized zirconia), and a porous phase is known to increase the electrochemical reactivity as well as the connectivity of the porous electrode. It is widely accepted that the preparation of NiO/YSZ composite powders is an effective way of generating better anode microstructures [1][2][3]. Various preparation methods such as spray pyrolysis, mechanical milling, and gel combustion have been studied for producing composite powders [4][5][6][7][8][9][10].…”