Core–shell-structured CNT@hydrous RuO2 as a H2/CO2 fuel cell cathode catalyst to promote CO2 methanation and generate electricity

Abstract

H₂/CO₂ fuel cells are important devices that convert CO₂ into CH₄ while generating electricity at mild temperatures. Anhydrous ruthenium oxide (RuO₂) on carbon nanotubes (CNT) as a cathode catalyst causes CO₂ methanation, but the methane production rate needs to be improved. In this paper, a core–shell structure of CNT@hydrous RuO₂ was fabricated by a simple sol–gel method. Unlike anhydrous RuO₂, which is a single electronic conductor, CNT@hydrous RuO₂ is a proton–electron mixed conductive material. Therefore, protons transfer not only in thepolybenzimidazole (PBI) film but also in the catalyst layer with the assistance of crystalline water in hydrous RuO₂. CO₂ methanation involving a reaction of multiple protons and electrons can be accelerated. The methane generation rate of CNT@hydrous RuO₂ reached 331.2 μmol g_cat⁻¹ h⁻¹ at 190 °C which is 3 times higher than that of anhydrous RuO₂. This research result provides an effective strategy for the catalytic reaction of multiple proton–electron transfers.