Low temperature solid oxide fuel cells with proton-conducting Y:BaZrO3 electrolyte on porous anodic aluminum oxide substrate

Abstract

This paper presents the architecture of a nano thin-film yttrium-doped barium zirconate (BYZ) solid-oxide fuel cell that uses nanoporous anodic aluminum oxide (AAO) as a supporting and gas-permeable substrate. The anode was fabricated by sputtering 300nm platinum thin film that partially covered the AAO surface pores, followed by an additional conformal platinum coating to tune the pore size by atomic layer deposition. Two different nano-porous anode structures with a pore size of 10nm or 50nm were deposited. Proton-conducting BYZ ceramic electrolyte with increasing thicknesses of 300, 600, and 900nm was deposited on top of the platinum anode by pulsed laser deposition, followed by a 200nm layer of porous Pt sputtered on BYZ electrolyte as a cathode. The open circuit voltage (OCV) of the fuel cells was characterized at 250°C with 1:1 volumetric stoichiometry of a methanol/water vapor mixture as the fuel. The OCVs were 0.17V with a 900nm-thick BYZ electrolyte on 50nm pores and 0.3V with a 600nm-thick BYZ electrolyte on 10nm pores, respectively, but it increased to 0.8V for a 900nm-thick BYZ electrolyte on 10nm pores, indicating that increasing the film thickness and decreasing a surface pore size help to reduce the number of electrolyte pinholes and the gas leakage through the electrolyte. A maximum power density of 5.6mW/cm2 at 250°C was obtained from the fuel cell with 900nm of BYZ electrolyte using methanol vapor as a fuel.