Nanoporous B₁₃C₂ towards Highly Efficient Electrochemical Nitrogen Fixation

Abstract

The electrochemical nitrogen fixation under mild conditions is a promising alternative to the current nitrogen industry with high energy consumption and greenhouse gas emission. Here, a nanoporous boron carbide (np‐B13C2) catalyst is reported for electrochemical nitrogen fixation, which is fabricated by the combination of metallurgical alloy design and chemical etching. The resulting np‐B13C2 exhibits versatile catalytic activities towards N2 reduction reactions (NRR) and N2 oxidation reaction (NOR). A high NH3 yield of 91.28 µg h−1 mgcat.−1 and Faradaic efficiency (FE) of 35.53% at −0.05 V versus the reversible hydrogen electrode are obtained for NRR, as well as long‐term stability of up to 70 h, making them among the most active NRR electrocatalysts. This catalyst can also achieve a NO3− yield of 165.8 µg h−1 mgcat.−1 and a FE of 8.4% for NOR. In situ Raman spectroscopy and density functional theory calculations reveal that strong coupling between the BC sites modulates the electronic structures of adjacent B atoms of B13C2, which enables the B sites to effectively adsorb and activate chemical inert N2 molecules, resulting in lowered energy required by the potential‐determining step. Besides, the introduction of carbon can increase the inherent conductivity and reduce the binding energy of the reactants, thus improving N2 fixation performance.

Catalytic Kinetics Regulation for Enhanced Electrochemical Nitrogen Oxidation by Ru‐Nanoclusters‐Coupled Mn3O4 Catalysts Decorated with Atomically Dispersed Ru Atoms

“…After the first work by Zhang et al, [13,14] the electrochemical N 2 oxidation reaction (NOR), using water and N 2 in the atmosphere (78%), has been demonstrated as a sustainable and promising approach for nitric production. [14][15][16][17][18][19][20][21] Electrochemical NOR is an endothermic and entropy-reducing process, [22,23] involving activation of N 2 , adsorption of OH (*OH), and multielectron transfer at "gas-liquid-solid" three-phase interface. This process is hindered by the slow cleavage of the N≡N bond owing to its high bond energy (941 kJ mol −1 ) and insurmountable first-bond dissociation energy (410 kJ mol −1 ).…”

“…In previous studies, OER-inactive catalysts and carriers were served to restrain competitive OER, and gained reasonable performance. [13][14][15][16][17][18][19][20][21] However, simply suppressing OER would reduce the activation of N 2 , the supply of *OH and sacrifice the inherently low activity towards NOR, insufficient to obtain satisfactory performance. Besides, on count of the obvious difference in dynamics between OER and NOR, electron transfer also largely affect the catalytic selectivity.…”

Progress of electrochemical Synthesis of Nitric Acid: Catalyst Design-Mechanistic insights-Protocol-Challenges

“…[56][57] It is not technically possible to synthesize a metal-free electrocatalyst using a traditional method because it is very difficult to simultaneously maintain the structure and composition of the material. [58][59] Yongwen Tan and coworkers [29] recently reported a nanoporous boron carbide (np-B13C2) which can be made by a combination of metallurgical alloy design and chemical etching (Figure 4a). The np-B13C2 shows high catalytic activity and long stability for nitrogen oxidation, which is comparable to the most reported electrocatalysts (comparison in Table 2).…”

“…[19] Therefore, it is still difficult to identify a suitable catalyst to activate nitrogen molecules and effectively drive the nitrogen oxidation reaction. Electrochemical dinitrogen oxidation process (N2OR) using various heterogeneous catalysts, such as Ru/TiO2, Pd-MXene, ZnFexCo2-xO4, Fe-SnO2, Nb2O5-x, Pd-s PNSs, etc., [21][22][23][24][25][26][27][28][29][30] under ambient circumstances, are an optimize promising alternative to generate sustainable nitrate products.…”

“…Figure 4: (a) Schematic for fabrication of 3D np-B13C2 (b) N2 adsorption sites on np-B13C2 with B1, B2, C sites (B1, boron atom adjacent to the carbon atom; B2, boron atom far from the carbon atom). (c) N2 adsorption energy (EN2) on B1, B2, C sites [29]. …”