Theoretical understanding of CO reduction products on nitrogen-doped graphene supported dual-atom catalysts.

In recent years, nitrogen-doped graphene supported dual-atom catalysts (DAC@NC) for the CO reduction reaction (CORR) have attracted widespread research interest. Although some DAC structures for deep reduction C products and C products have been proposed in previous theoretical calculations, the desired products are still difficult to be realized in experiments. This work systematically investigates the reaction pathways and products of CO reduction on bimetallic DAC@NC (M-M@NC, M, M = Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, and Pt) by first-principles calculations. After excluding improper M-M@NC due to catalyst poisoning and hydrogen evolution competition, C-C coupling processes always have much higher free-energy increments than the corresponding hydrogenation, making it difficult to form multi-carbon structures. For most of the C intermediates on M-M@NC, the free-energy increments of C-C coupling are higher than 0.8 eV. Some C intermediates could couple with a second carbon, but this process is much more difficult than hydrogenation toward C products. This work reveals why C products are still difficult to be achieved for the CORR on M-M@NC and identifies the M-M combinations for deep reduction C products (methane and methanol), which is inspiring for the future design of CORR catalysts.