Electrochemical Nitrogen Reduction Reaction Performance of Single-Boron Catalysts Tuned by MXene Substrates

A boron (B) center, which has an electronic structure mimicking the filled and empty d orbitals in transition metals, can effectively activate the triple bond in N-2 so as to catalyze the nitrogen reduction reaction (NRR). Here, by means of density functional theory, we have systematically investigated the catalytic performance of a single B atom decorated on two-dimensional transition metal carbides (MXenes). The B-doped Mo2CO2 and W2CO2 MXenes exhibit outstanding catalytic activity and selectivity with limiting potentials of -0.20 and -0.24 V, respectively. Importantly, we have found that, although a high tendency of B-to-adsorbate electron donation can promote the hydrogenation of *N-2 to *N2H, it would also severely hamper the *NH2 to *NH3 conversion due to the strong B-N bonding. Such an electron-donation effect can be reasonably tuned by the transition metal in the MXene substrate, which enables us to achieve optimized catalytic performance with a certain moderate degree of electron donation.