Coke-free direct formic acid solid oxide fuel cells operating at intermediate temperatures

Abstract

Formic acid is investigated as a fuel for Solid Oxide Fuel Cells (SOFCs) for the first time. Thermodynamic calculations demonstrate that carbon deposition is avoidable above 600 °C. The carbon deposition properties are also investigated experimentally by first treating a nickel plus yttria-stabilized zirconia (Ni–YSZ) anode material in particle form under a formic acid-containing atmosphere for a limited time at 500–800 °C and then analyzing the particles by O2-TPO. This analysis confirms that carbon deposition on Ni–YSZ is weak above 600 °C. We further treat half-cells composed of YSZ electrolyte and Ni–YSZ anode under formic acid-containing atmosphere at 600, 700 and 800 °C; the anodes maintain their original geometric shape and microstructure and show no obvious weight gain. It suggests that formic acid can be directly fed into SOFCs constructed with conventional nickel-based cermet anodes. I–V tests show that the cell delivers a promising peak power density of 571 mWcm−2 at 800 °C. In addition, the cells also show good performance stability. The results indicate that formic acid is highly promising as a direct fuel for SOFCs without the need for cell material modifications.