Theoretical study on borophene as metal-free catalyst for selective conversion of NO

Abstract

The electrocatalytic reduction of NO (NORR) and selective catalytic reduction of NO by CO (CO-SCR) are the two most attractive approaches for selective conversion of NO. Herein, a bifunctional metal-free catalyst 2-Pmmn borophene is reported that is effective for both NORR and CO-SCR. NO can form NH3 and N2 through NORR and CO-SCR respectively. The results show that NO chemically adsorbed on the surface of borophene through the NO terminal can be electrocatalytically reduced to NH3. The optimal reaction path for NO to generate NH3 is through the protonation process of *NHO instead of *NOH. The rate-determining step is the hydrogenation of *NH2O to *NH2OH, and the free energy increases by 0.41 eV. At the same time, NO can also react with CO on the surface of borophene to form N2 and CO2. First, NO can form chemically adsorbed ONNO intermediate through NN coupling, then ONNO can be denitrified to form N2 and residual oxygen, and finally residual oxygen and CO can generate CO2 through the LH mechanism. The rate-determining step of the reaction is the NN coupling process of NO, and activation energy barrier is 1.27 eV. The present work provides theoretical insights for the effective conversion of NO.