Design of Active Sites on Nickel in the Anode of Intermediate-Temperature Solid Oxide Fuel Cells using Trace Amount of Platinum Oxides
Abstract
In recent years, the lowering of the operation temperature of solid oxide fuel cells (SOFCs) has attracted much attention owing to the trade-off between the best performance and the life span of SOFCs. For this challenge, new active sites on the Ni surfaces in a Nickel-Yttria-Stabilized Zirconia (Ni-YSZ) cermet anode of SOFCs have been created by deposition of trace amounts of platinum oxide (PtOx) followed by an activation step of the anode at 1073K in a hydrogen flow.
The internal resistance (IR) free value (185mAcm(-2) at 0.8V) observed for the single cell with an anode sputtered with a trace amount of PtOx (Pt content in anode: from 9 to 91ppm) at 973K is conspicuously higher than that of a similar single cell with a nonsputtered cermet anode (85mAcm(-2)) at 0.8V and 1073K. Transmission electron microscopy microanalysis shows that the defect structure is formed on a partially oxidized Ni surface by active Pt species.
Also, surface atomistic simulation on NiO (111) predicts the formation of Frenkel defect clusters with Pt cations, which partially cover the Ni surface. The formation of Frenkel defect clusters on the partially oxidized Ni surface (i.e., creation of new active sites for formation of water molecules) promotes the anode reaction, resulting in improvements in the anode performance of SOFC single cells at 973K.
Design of the aforementioned new active sites on Ni through sputtering of trace amounts of PtOx provides a great opportunity for radical innovation in the design of intermediate-temperature SOFCs.