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

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 g_cat.^-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.