Biogas sequestration to carbon nanofibers via tandem catalytic strategies

Abstract

Upgrading decentralized biogas represents a sustainable route to produce valuable products while mitigating two potent greenhouse gases, namely, methane (CH4) and carbon dioxide (CO2). Conventional dry reforming of CH4 with CO2 yields syngas with low H2/CO ratios (≤1) and requires high temperatures (>800 °C) to overcome equilibrium constraints and abate coke deposition, which limits commercial implementation. Here we demonstrate the conversion of biogas into value-added carbon nanofibers via reaction integration in tandem reactors, while reducing the reaction temperature, shifting equilibrium limits and yielding H2-enriched syngas (H2/CO = 2–3) as a byproduct. Experimental and theoretical insights reveal that potassium (K) modification enhances carbon nanofiber formation due to synergistic effects via a balanced interplay between KOx-induced cobalt facets and cobalt carbide species. The energy cost and CO2 footprint analyses highlight the potential advantages of tandem processes for the sustainable upgrading of biogas into valuable solid carbon products. Upgrading biogas to valuable solid carbon can potentially lead to negative CO2 emissions with long-term carbon storage but faces substantial thermodynamic and kinetic limits using a single reactor. Tandem strategies can decouple reactions into tandem reactors, integrate non-equilibrium processes and identify synergistic catalytic sites to enhance carbon nanofiber production.