cs9b04103_si_001.pdf (972.83 kB)
Isolated Boron Sites for Electroreduction of Dinitrogen to Ammonia
journal contribution
posted on 2020-01-15, 03:03 authored by Xin Liu, Yan Jiao, Yao Zheng, Shi-Zhang QiaoExploring electrocatalysts
with high activity is essential for
the production of ammonia via an electrochemical routine. By employing
density functional theory calculations, we investigated the electrochemical
nitrogen reduction reaction (eNRR) activity on binary metal borides,
a model system of metal borides. To elaborate the mechanisms, molybdenum
borides (Mo2B, α-MoB, and MoB2) were first
modeled; the results indicate that the crystal structures greatly
impact the N2 adsorption and therefore the electrocatalytic
activity. Our electronic structure investigation suggests that boron
p-orbital hybrids with dinitrogen π*-orbital, and the population
on p−π*-orbital determine the N2 adsorption
strength. Therefore, the isolated boron site of Mo2B with
less filled pz-orbital benefits the activation
of N2 and weaken the triple bond of dinitrogen. This isolated
boron sites concept was successfully extended to other metal borides
in the form of M2B (M stands for Ti, Cr, Mn, Fe, Co, Ni,
Ta, W). Mo2B, Fe2B, and Co2B were
discovered as the most promising candidates with low limiting potentials
due to appropriate adsorption strength of reaction intermediates led
by moderate pz filling. This work provides
insights for designing metal borides as promising eNRR electrocatalysts.