Atomic Ru Immobilized on Porous h-BN through Simple Vacuum Filtration for Highly Active and Selective CO₂ Methanation

Abstract

As CO2 emissions are sharply increasing, processes for converting CO2 into value-added products are becoming more desirable. Ruthenium-based catalysts are the most active for CO2 methanation; however, their substantially higher cost relative to transition metals makes them prohibitive for industrial application. In this study, we demonstrate porous hexagonal boron nitride (pBN) supports (an ideal support material for thermocatalysts due to the high thermal stability and conductivity) to improve the utilization of Ru and simultaneously enhance the catalytic activity and selectivity for CO2 methanation. A simple vacuum filtration process is proposed that allows the Ru precursor to quickly locate the defects of pBN, where atomic Ru can be restricted onto the defects via B, N coordination through an annealing treatment. The B and N coordinations reduce the valence state of atomic Ru. The as-prepared catalyst with low Ru loading (0.58 wt %) exhibits CH4 selectivity up to 93.5%, catalytic stability after 110 h, and a higher reaction rate [1.86 mmolCO2/(gcat s)] at 350 °C and 1.0 MPa compared to other nanoparticle catalysts. Both atomic-scale size and low valence state of atomic Ru supported on pBN are responsible for the improvement of CH4 production rate as confirmed by density functional theory simulation.