Call Douglas F, Merrill Matthew D, Logan Bruce E
Hydrogen Energy Center and Department of Civil and Environmental Engineering, 212 Sackett Building, Penn State University, University Park, Pennsylvania 16802, USA.
Environ Sci Technol. 2009 Mar 15;43(6):2179-83. doi: 10.1021/es803074x.
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 m2/m3, hydrogen was produced at a rate of 1.7 +/- 0.1 m3-H2/m3-d (current density of 188 +/- 10 A/m3) 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/m3 to 78 +/- 4 A/m3. A brush cathode with graphite instead of stainless steel and a specific surface area of 4600 m2/m3 generated substantially less current (1.7 +/- 0.0 A/m3), and a flat stainless steel cathode (25 m2/m3) produced 64 +/- 1 A/m3, 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.
微生物电解池（MECs）是一种利用有机物产生氢气的高效技术，但阴极催化剂需要贵金属的替代物。我们在此表明，高表面积不锈钢刷式阴极产生氢气的速率和效率与单室MECs中铂催化碳布阴极所达到的速率和效率相似。使用比表面积为810 m²/m³的不锈钢刷式阴极，在0.6 V的外加电压下，氢气产生速率为1.7±0.1 m³-H₂/m³-d（电流密度为188±10 A/m³）。相对于电能输入的能量效率为221±8%，基于电能和底物利用的总能量效率为78±5%。这些值与之前在类似系统中使用平板碳阴极上的铂所获得的结果相当。将阴极表面积减少75%会使性能从91±3 A/m³降至78±4 A/m³。具有石墨而非不锈钢且比表面积为4600 m²/m³的刷式阴极产生的电流大幅减少（1.7±0.0 A/m³），而平板不锈钢阴极（25 m²/m³）产生64±1 A/m³，这表明不锈钢和大表面积都有助于实现高电流密度。线性扫描伏安法表明，不锈钢刷式阴极既降低了析氢所需的过电位，又由于活化作用随着时间推移过电位降低。这些结果首次证明，在MECs中无需昂贵阴极即可实现与贵金属催化剂相当的氢气产生速率。
