Ordered mesoporous carbon spheres assisted Ru nanoclusters/RuO2 with redistribution of charge density for efficient CO2 methanation in a novel H2/CO2 fuel cell

Abstract

Efficiently reducing carbon dioxide (CO2) into carbon chemicals and fuels is highly desirable due to the rapid growth of atmospheric CO2 concentration. In prior work, we described a unique H2/CO2 fuel cell driven by low-valued waste heat, which not only converts CO2 to methane (CH4) but also outputs electrical energy, yet the CO2 reduction rate needs to be urgently improved. Here, a novel Ru-RuO2 catalyst with heterostructure was grafted on mesoporous carbon spheres by in situ partially reducing RuO2 into ultrasmall Ru clusters (∼1 nm), in which heteroatom-doped carbon spheres as a matrix with excellent conductivity and abundant pores can not only easily confine the formation of Ru nanocluster but also are beneficial to the exposed active sites of Ru complex and the mass transport. Compared to pure RuO2 nanoparticles supported on carbon spheres, our composite catalyst boosts the CO2 conversion rate by more than 5-fold, reaching a value of 382.7 μmol gcat.-1h−1 at 170 ℃. Moreover, a decent output power density of 2.92 W m−2 was obtained from this H2/CO2 fuel cell using Ru-RuO2 embedded carbon spheres as a cathode catalyst. The Ru-RuO2 heterostructure can modify the adsorption energy of CO2 and induce the redistribution of charge density, thus boosting CO2 reduction significantly. This work not only offers an efficient catalyst for this novel H2/CO2 fuel cell but also presents a facile method to prepare Ru nanoclusters.