Metal-Free Boron Nitride Nanoribbon Catalysts for Electrochemical CO2 Reduction: Combining High Activity and Selectivity.

Abstract

Developing metal-free catalysts for reduction of CO2 into energy-rich products is a popular yet very challenging topic. Using density functional theory calculations, we investigated the electrocatalytic performance of C-doped and line-defect (Ld)-embedded boron nitride nanoribbons (BNNRs) for CO2 reduction reaction (CRR). Because of the presence of bare edge B atoms neighboring to C dopant and C2 dimer as active sites, defective BNNRs exhibit high CRR catalytic activity and selectivity. The Ld-embedded BNNR structures with C2 dimer can not only convert CO2 into CO with very low overpotential of -0.5 V versus reversible hydrogen electrode but also ensure high selectivity in deactivating the hydrogenation channel of the desorbed CO to CH4. The C-doped zigzag and armchair BNNRs bind strongly to the CO intermediate and thus promote the selective conversion of CO2 to CH4, with the lower energy cost on the armchair ribbon than the zigzag one. The presence of edge B atoms and C dopant as dual active sites in BNNRs enables effective couplings between *CH2 and CO intermediates, leading to the formation of C2 products including C2H4 and C2H5OH, with a high selectivity for C2H5OH. Importantly, unwanted hydrogen evolution reaction is suppressed during CRR catalyzed by these BNNR-based configurations. Overall, the present findings highlight a promising new class of low-cost, metal-free electrocatalysts combining high CRR activity and selectivity.