A CO2/H2 fuel cell: reducing CO2 while generating electricity

Abstract

Electrocatalytic conversion of CO₂ into hydrocarbons is one of the most promising approaches to reduce the concentration of CO₂ in the atmosphere as well as to produce various valuable chemical products from this most prevalent greenhouse gas. However, this process is still many steps away from finding practical application because of its high energy demand. Herein we report an innovative CO₂/H₂ fuel cell that can convert CO₂ into a synthetic fuel (CH₄) while generating electricity instead of consuming it. This is unlike conventional electrochemical CO₂ reduction cells, which typically consume electricity to reduce CO₂. In the new cell, H₂ is oxidized to H⁺ ions (and electrons) at the anode, and the H⁺ ions then pass through a proton exchange membrane to reduce CO₂ to CH₄ at the cathode. While doing so, the cell can generate a current density of 94.1 A m⁻², a peak power density of 3.9 W m⁻² and CH₄ at a rate of 75.29 μmol g_cat⁻¹ h⁻¹ at 170 °C, a temperature that can be derived from waste heat from various processes. Density functional theory is applied to determine the reaction mechanism on the catalyst in the cell.