Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
Water Res. 2024 Aug 1;259:121815. doi: 10.1016/j.watres.2024.121815. Epub 2024 May 21.
Microbial electrosynthesis (MES) cells exploit the ability of microbes to convert CO into valuable chemical products such as methane and acetate, but high rates of chemical production may need to be mediated by hydrogen and thus require a catalyst for the hydrogen evolution reaction (HER). To avoid the usage of precious metal catalysts and examine the impact of the catalyst on the rate of methane generation by microbes on the electrode, we used a carbon felt cathode coated with NiMo/C and compared performance to a bare carbon felt or a Pt/C-deposited cathode. A zero-gap configuration containing a cation exchange membrane was developed to produce a low internal resistance, limit pH changes, and enhance direct transport of H to microorganisms on the biocathode. At a fixed cathode potential of -1 V vs Ag/AgCl, the NiMo/C biocathode enabled a current density of 23 ± 4 A/m and a high methane production rate of 4.7 ± 1.0 L/L-d. This performance was comparable to that using a precious metal catalyst (Pt/C, 23 ± 6 A/m, 5.4 ± 2.8 L/L-d), and 3-5 times higher than plain carbon cathodes (8 ± 3 A/m, 1.0 ± 0.4 L/L-d). The NiMo/C biocathode was operated for over 120 days without observable decay or severe cathode catalyst leaching, reaching an average columbic efficiency of 53 ± 9 % based on methane production under steady state conditions. Analysis of microbial community on the biocathode revealed the dominance of the hydrogenotrophic genus Methanobacterium (∼40 %), with no significant difference found for biocathodes with different materials. These results demonstrated that HER catalysts improved rates of methane generation through facilitating hydrogen gas evolution to an attached biofilm, and that the long-term enhancement of methane production in MES was feasible using a non-precious metal catalyst and a zero-gap cell design.
微生物电化学合成（MES）细胞利用微生物将 CO 转化为有价值的化学产品（如甲烷和乙酸盐）的能力，但高化学产物的生成速率可能需要由氢气介导，因此需要一种催化剂来进行氢气析出反应（HER）。为了避免使用贵金属催化剂并研究催化剂对微生物在电极上生成甲烷速率的影响，我们使用了涂有 NiMo/C 的碳纤维毡阴极，并将其性能与裸碳纤维毡或 Pt/C 沉积阴极进行了比较。开发了一种具有阳离子交换膜的零间隙配置，以产生低内阻、限制 pH 值变化并增强 H 向生物阴极上微生物的直接传输。在固定的-1 V 对 Ag/AgCl 阴极电位下，NiMo/C 生物阴极可实现 23 ± 4 A/m 的电流密度和 4.7 ± 1.0 L/L-d 的高甲烷生成速率。这种性能与使用贵金属催化剂（Pt/C，23 ± 6 A/m，5.4 ± 2.8 L/L-d）相当，比普通碳阴极高 3-5 倍（8 ± 3 A/m，1.0 ± 0.4 L/L-d）。NiMo/C 生物阴极在没有观察到衰减或严重阴极催化剂浸出的情况下运行了 120 多天，在稳态条件下基于甲烷生成达到了 53 ± 9%的平均库仑效率。对生物阴极上微生物群落的分析表明，氢营养型属 Methanobacterium（约 40%）占主导地位，不同材料的生物阴极之间没有发现显著差异。这些结果表明，HER 催化剂通过促进氢气向附着生物膜的析出来提高甲烷生成速率，并且使用非贵金属催化剂和零间隙电池设计可以实现 MES 中甲烷生成的长期增强。
