Boron Nitride Nanotubes for Ammonia Synthesis: Activation by Filling Transition Metals

Abstract

Boron nitride (BN), with outstanding stability and robustness in diverse polymorphs, possesses many advantageous properties for industrial applications. Activation of BN materials for nonmetal catalysts is among the most revolutionary and challenging tasks. Taking advantage of quantum size effect and synergistic effect, here we exploit boron nitride nanotubes (BNNTs) encapsulating early transition metal nanowires, which is experimentally feasible, for nitrogen fixation and ammonia synthesis. Using firstprinciples calculations and microkinetic modeling, we show that the coexisting occupied and unoccupied p states of B atoms in filled BNNTs can effectively mimic the d states of transition metal. They act as electron reservoirs with tunable orbital energies and occupancy, which are beneficial for associative N 2 adsorption and hydrogenation. Due to the competition between thermodynamics of gas adsorption and kinetics of hydrogenation reaction, the activity can be optimized by controlling the type of metal filler and size of BN nanotube, achieving a turnover frequency competitive to that of benchmark Fe catalyst. These results manifest a universal strategy for activating BN nanomaterials as a promising family of robust and efficient catalysts and provide vital insights into the activity− band structure relationship for p-block nonmetal catalysts.

Rational Design of High‐Concentration Ti3+ in Porous Carbon‐Doped TiO2 Nanosheets for Efficient Photocatalytic Ammonia Synthesis

“…To date, some precious metal catalysts (eg., Au, Ru) and various semiconductors, including ZnO, BiOBr, and W 18 O 49 , boron nitride, layered double hydroxides, and graphitic carbon nitride have been studied as active photocatalysts for the reduction of N 2 . [ 11–21 ] With these advances in mind, the photocatalytic NH 3 production rate is currently still hindered by its slow reaction kinetics and low efficiency.…”

Anchoring Mo on C9N4 monolayers as an efficient single atom catalyst for nitrogen fixation

“…So far, various approaches including biocatalysis, electrocatalysis, bioelectrocatalysis [11], photocatalysis and molecular catalysis [12,13], have been explored for NH 3 synthesis. Among these methods, electrochemical nitrogen reduction reaction (NRR) under the ambient condition is particularly promising because of its relatively low energy input and zero CO 2 emission [14][15][16][17][18][19][20]. However, owing to the fact that the bonding energy of N"N triple bond is extremely high (945 kJ/mol), N 2 activation is commonly recognized as the major rate-determining step (RDS) for NH 3 synthesis.…”

Highly efficient ammonia synthesis at low temperature over a Ru–Co catalyst with dual atomically dispersed active centers

“…[1][2][3][4][5][6][7] The potential utilization of NH 3 in the coming chemical industry revolution is highly promising. 8 Unfortunately, the industrial synthesis of NH 3 via the Haber-Bosch (HB) process using ironbased catalysts requires stringent reaction conditions (400-600 C, 20-40 MPa), [9][10][11][12] and consumes 1-2% of the global energy and produces $1.5 tons of carbon dioxide per ton of NH 3 . [10][11][12] Traditionally, the H 2 supply for the HB process is mainly from coal or natural gas through the water-gas shi (WGS) or methane reforming reaction, 13 and these processes account for the energy requirement and carbon dioxide production.…”