Optimizing the power of enzyme-based membrane-less hydrogen fuel cells for hydrogen-rich H-2-air mixtures

Journal article

The unusual ability of O2-tolerant hydrogenases (H 2ase) to produce electricity from a H2-air mixture (when used as the anodic electrocatalyst in a simple, membrane-less fuel cell) is investigated with the aim of establishing a strategy for raising volume power density, the measure of importance for miniature devices. Compacted mesoporous carbon electrodes provide a simple and inexpensive method for obtaining a large increase in productive enzyme loading, greatly increasing current densities and stability. Operated under a 78% H2-22% air mixture at 25 °C, typical current densities at a stationary H2ase anode and bilirubin oxidase cathode are 4.60 ± 0.32 mA cm-2 and 1.23 ± 0.12 mA cm-2, respectively. The power limitation due to low O2 concentration is addressed by re-proportioning the cathode/anode area ratio to balance the cathodic and anodic currents. At room temperature, the maximum power density of the fuel cell with an anode/cathode (A/C) ratio of 1:3 (1A/3C) is 1.67 ± 0.24 mW cm-2 (per anode area) or 0.42 ± 0.06 mW cm-2 (per total area). Good prospects for stability are demonstrated by the fact that 90% of the power is retained after continuously working for 24 h, and more than half of the power is retained after one week of non-stop operation. Using an even weaker O2 mixture (89% H2, 11% air) the 1A/3C cell gives over 0.8 mW cm-2 (anode) or 0.2 mW cm -2 (total electrode area). The results demonstrate the feasibility of membrane-less hydrogen-air fuel cells delivering volume power densities well in excess of 1 mW cm-3. © The Royal Society of Chemistry 2013.

Authors: Xu, L; Armstrong, F

• Publication status: Published
• Journal: ENERGY and ENVIRONMENTAL SCIENCE
• Volume: 6
• Issue: 7
• Pages: 2166-2171
• Publication date: 2013-07-01
• DOI: 10.1039/c3ee40791h
• EISSN: 1754-5706
• ISSN: 1754-5692
• Language: English