Bioelectrochemical power-to-gas presents a promising technology for long-term storage of excess renewable energy in the form of methane. The transition of the technology from laboratory to applied scale is currently challenged by low volumetric production rates, energy losses at the cathode, as well as the unknown physiology of the microbes in an electrochemical reactor. Here, we introduce a stable electromethanogenesis system based on efficient in situ hydrogen production by non-precious-metal catalysts and effective hydrogen uptake by the methanogenic microorganisms. Using NiMo-cathodes and pure cultures of hydrogenotrophic Methanococcus maripaludis, our system achieved an unprecedented volumetric methane production rate from CO₂ of 1.4 L methane per L per day. The system performed stably for over 4 weeks with columbic efficiencies steadily above 90%. A physiological analysis of cells in the electromethanogenic reactor revealed robustly-growing cells with nearly identical protein expression patterns to gas-fed controls. Local pH fluctuations at the surface of cathode and cation exchange membrane resulted in a small but noticeable fraction of cell lysis. Our data collectively indicate that physiologically uncompromised cells of a pure methanogenic culture can perform methanogenesis robustly at high specific rate in a biocompatible electromethanogenic reactor using inexpensive, earth-abundant cathode materials.

中文翻译：

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原位电化学生产H2以实现高效稳定的燃气制电甲烷生成

生物电化学转化为天然气提出了一种有前途的技术，可以长期存储甲烷形式的多余可再生能源。目前，该技术从实验室到应用规模的过渡面临着低体积生产率，阴极能量损失以及电化学反应器中微生物未知生理的挑战。在此，我们介绍一种稳定的电甲烷生成系统，该系统基于通过非贵金属催化剂有效地原位产生氢气和甲烷化微生物有效地吸收氢气的能力。使用NiMo阴极和纯营养的马氏甲烷氧化球菌，我们的系统从CO _2中获得了空前的甲烷产量每天每升1.4升甲烷。该系统稳定运行了超过4周，其哥伦比亚效率稳定在90％以上。对产甲烷的电甲烷反应器中的细胞进行的生理学分析显示，与气体喂养的对照相比，细胞生长强劲，蛋白质表达模式几乎相同。阴极和阳离子交换膜表面的局部pH波动导致细胞裂解的比例很小但很明显。我们的数据共同表明，纯粹的产甲烷培养物在生理上不受影响的细胞可以在使用廉价的地球上丰富的阴极材料的生物相容性电甲烷反应器中以高比速率稳健地进行产甲烷作用。