Author's personal copy Evaluation of stainless steel cathodes and a bicarbonate buffer for hydrogen production in microbial electrolysis cells using a new method for measuring gas production

Microbial electrolysis cells (MECs) are often examined for hydrogen production using nonsustainable phosphate buffered solutions (PBS), although carbonate buffers have been shown to work in other bioelectrochemical systems with a platinum (Pt) catalyst. Stainless steel (SS) has been shown to be an effective catalyst for hydrogen evolution in MECs, but it has not been tested with carbonate buffers. We evaluated the combined using of SS cathodes and a bicarbonate buffer (BBS) at the applied voltages of 0.5, 0.7 and 0.9 V using a new inexpensive method for measuring gas production called the gas bag method (GBM). This method achieved an average error of only 5.0% based on adding known volumes of gas to the bag. Using the GBM, hydrogen production with SS and a BBS was 26.6 1.8 mL which compared well to 26.4 2.8 mL using Pt and BBS, and 26.8 2.5 mL with a Pt cathode and PBS. Electrical energy efficiency was highest with a SS cathode and BBS at 159 17%, compared to 126 14% for the Pt cathode and BBS, and 134 17% for a Pt cathode and PBS. The main disadvantage of the SS was a lower gas production rate of 1.1 0.3 mH2-m 3 d 1 with BBS and 1.2 0.3 mH2-m 3 d 1 with PBS, compared to 1.7 0.4 mH2-m 3 d 1 with Pt and PBS. These results show that the GBM is an effective new method for measuring gas production of anaerobic gas production processes, and that SS and bicarbonate buffers can be used to effectively produce hydrogen in MECs. a 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.