Prediction of single-boron anchored on MXene catalysts for high-efficient electrocatalytic nitrogen reduction reaction

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The design of efficient catalysts plays an important role in the development of electrochemical nitrogen reduction reaction (NRR). 2D materials MXene can be used as promising catalyst substrates in NRR due to their superior chemical stability and conductivity. Here, using density functional theory calculations, 9 kinds of single-atom catalysts (SACs) B@M3C2O2-x (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W) were constructed by anchoring electron-deficient non-metal boron atom on M3C2O2-x with one terminal-O vacancy. All SACs have good thermodynamic and electrochemical stability. The strong acceptor-donor interaction between B atom and N2 molecule leads to the activation of N2, thus promoting NRR. We adopted the screening strategies, including comparing the free energy of N2 adsorption, the free energy changes for the first and last electrochemical steps of NRR, and the selectivity of hydrogen evolution reaction (HER). Finally, five candidate catalysts (B@V3C2O2-x, B@Cr3C2O2-x, B@Nb3C2O2-x, B@Mo3C2O2-x and B@W3C2O2-x) were screened out. Starting from the end-on adsorption mode of N2, NRR proceeds through a mixed mechanism on each SAC. Our results show that these five SACs have excellent catalytic performance with the limiting potentials ranging from -0.32 to -0.48 V, which may be promising NRR electrocatalysts.