Hexagonal boron nitride nanoribbon as a novel metal-free catalyst for high-efficiency NO reduction to NH3

Electrochemical NO reduction is taken as a promising avenue to eliminate detrimental NO into valuable NH3 for a balanced nitrogen cycle. Current electrocatalysts for NO reduction are mainly focused on metal-bearing catalysts, while metal-free catalysts with low cost, excellent stability, activity and selectivity are strongly desired. Herein, we report hexagonal boron nitride nanoribbons (BNNRs) as novel metal-free catalysts for efficient NO adsorption and reduction into NH3. Our results reveal that bare edge B atoms of armchair and zigzag BNNRs act as active sites for spontaneous chemisorption and activation of NO, originating from significant electron transfer. Notably, in the subsequent NO reduction, NH3 can be spontaneously produced by armchair BNNR with a limiting potential (UL) of 0 V, which is superior to most well-established single-atom, biatom and pure traditional metal catalysts. The awesome catalytic activity for NO reduction is intrinsically introduced by the suitable NO adsorption strength on armchair BNNR, which is illuminated to appropriate electronic interactions between the active site and NO. Moreover, the catalytic selectivity of armchair BNNR for NH3 production at both low and high NO coverage can be well guaranteed due to the higher thermodynamic energy barriers in generating N2O, N2 and H2. Overall, our findings pioneer the catalytic application of BNNR and unveil the veil of metal-free catalysts for direct NO reduction to NH3.