High surface area stainless steel brushes as cathodes in microbial electrolysis cells

Douglas F. Call, Matthew D. Merrill, Bruce E. Logan

Research output: Contribution to journalArticlepeer-review

170 Scopus citations

Abstract

Microbial electrolysis cells (MECs) are an efficient technology for generating hydrogen gas from organic matter, but alternatives to precious metals are needed for cathode catalysts. We show here that high surface area stainless steel brush cathodes produce hydrogen at rates and efficiencies similar to those achieved with platinum-catalyzed carbon cloth cathodes in single-chamber MECs. Using a stainless steel brush cathode with a specific surface area of 810 m 2/m 3, hydrogen was produced at a rate of 1.7 ± 0.1 m 3-H 2/m 3-d (current density of 188 ± 10 A/m 3) at an applied voltage of 0.6 V. The energy efficiency relative to the electrical energy input was 221 ± 8%, and the overall energy efficiency was 78 ± 5% based on both electrical energy and substrate utilization. These values compare well to previous results obtained using platinum on flat carbon cathodes in a similar system. Reducing the cathode surface area by 75% decreased performance from 91 ± 3 A/m 3 to 78 ± 4 A/m 3. A brush cathode with graphite instead of stainless steel and a specific surface area of 4600 m 2/m 3 generated substantially less current (1.7 ± 0.0 A/m 3), and a flat stainless steel cathode (25 m 2/m 3) produced 64 ± 1 A/m 3, demonstrating that both the stainless steel and the large surface area contributed to high current densities. Linear sweep voltammetry showed that the stainless steel brush cathodes both reduced the overpotential needed for hydrogen evolution and exhibited a decrease in overpotential over time as a result of activation. These results demonstrate for the first time that hydrogen production can be achieved at rates comparable to those with precious metal catalysts in MECs without the need for expensive cathodes.

Original languageEnglish (US)
Pages (from-to)2179-2183
Number of pages5
JournalEnvironmental Science and Technology
Volume43
Issue number6
DOIs
StatePublished - Mar 15 2009

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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