Suppressing Methane Production to Boost High-Purity Hydrogen Production in Microbial Electrolysis Cells

Abstract

Hydrogen gas (H2) is an attractive fuel carrier due to its high specific enthalpy; moreover, it is a clean source of energy because in the combustion reaction with oxygen (O2) it produces water as the only byproduct. The microbial electrolysis cell (MEC) is a promising technology for producing H2 from simple or complex organics present in wastewater and solid wastes. Methanogens and non-archaeal methane (CH4)-producing microorganisms (NAMPMs) often grow in the MECs and lead to rapid conversion of produced H2 to CH4. Moreover, non-archaeal methane production (NAMP) catalyzed by nitrogenase of photosynthetic bacteria was always overlooked. Thus, suppression of CH4 production is required to enhance H2 yield and production rate. This review comprehensively addresses the principles and current state-of-the-art technologies for suppressing methanogenesis and NAMP in MECs. Noteworthy, specific strategies aimed at the inhibition of methanogenic enzymes and nitrogenase could be a more direct approach than physical and chemical strategies for repressing the growth of methanogenic archaea. In-depth studies on the multiomics of CH4 metabolism can possibly provide insights into sustainable and efficient approaches for suppressing metabolic pathways of methanogenesis and NAMP. The main objective of this review is to highlight key concepts, directions, and challenges related to boosting H2 generation by suppressing CH4 production in MECs. Finally, perspectives are briefly outlined to guide and advance the future direction of MECs for production of high-purity H2 based on genetic and metabolic engineering and on the interspecific interactions.

Vulnerable Methanogenic Community in Microbial Electrolysis Cells Alters Electron Allocation in Response to Community Coalescence

“…50,51 Theoretically, the increased hydrogen production should be related to decreased methane generation. 50,52 However, we observed enhanced hydrogen evolution in conjunction with a stable methane yield (Figure S3d). It was obvious that the higher cathodic Coulombic efficiency should be ascribed to augmented hydrogen production, which could be caused by a lower methane sink at the cathode.…”

“…Although hydrogen evolution could be independent of microbial processes, the biocathode has been shown to produce hydrogen in MECs . Substantially, the main contributor of methane production was confirmed as methanogens in the cathodic biofilm via the hydrogenotrophic pathway. , Thereby, biomass retention on the electrode was verified as an important factor in determining its performance in methane production, as well as for hydrogen accumulation through the provision of an electron donor. , Theoretically, the increased hydrogen production should be related to decreased methane generation. , However, we observed enhanced hydrogen evolution in conjunction with a stable methane yield (Figure S3d). It was obvious that the higher cathodic Coulombic efficiency should be ascribed to augmented hydrogen production, which could be caused by a lower methane sink at the cathode.…”

Single‐Atom Co‐Ultrafine RuOx Clusters Codecorated TiO2 Nanosheets Promote Photocatalytic Hydrogen Evolution: Modulating Charge Migration, H+ Adsorption, and H2 Desorption of Active Sites

“…[ 1,2 ] Hydrogen (H 2 ) is considered a sustainable, clean, and environmentally friendly energy source with great potential as a future energy carrier due to its high energy density (142 MJ kg −1 ) and ability to be manufactured in a variety of ways. [ 3,4 ]…”

“…[1,2] Hydrogen (H 2 ) is considered a sustainable, clean, and environmentally friendly energy source with great potential as a future energy carrier due to its high energy density (142 MJ kg −1 ) and ability to be manufactured in a variety of ways. [3,4] Photocatalytic water splitting has been recognized as the most attractive way to produce H 2 . [5][6][7] However, extremely high recombination of photogenerated carriers limits the efficiency of most photocatalysts, which usually needs cocatalysts.…”

Improved Fe(II) regeneration from actual ferric sludge using a biocathode with granular sludge

“…Microbial electrolysis cells (MECs) has become a prospective and sustainable technology for high-efficiency chemical production (e.g., H 2 O 2 and H 2 ) from wastewaters (He et al, 2022;Li et al, 2016;Zhang and Angelidaki, 2014). Recently, our group found that dissolved Fe(II) can be regenerated from ferric sludge at near-neutral pH, in the biocathode of MEC (Guan Wang et al, 2022a).…”