C1 gas Ni–Co alloy TiO2 nanotube acetate acetosyringone anode distance anodic volume bioelectrochemical reactor bioelectrochemical system biogenic conversion carbon monoxide cathode coal dilution rate dye decolorization electrodialysis environmental engineering flow rate hydrogen production inhibition laccase lignite methane microbial electrolysis cell microbial fuel cell microbial fuel cell (MFC) natural redox mediators power density power generation renewable energy source