Electrocatalytic Nitrogen Reduction Performance of Si‐doped 2D Nanosheets of Boron Nitride Evaluated via Density Functional Theory

Abstract

Electrochemical nitrogen fixation under ambient conditions is proposed as a sustainable alternative to the traditional Haber‐Bosch method to combat both a global energy crisis and climate change. However, effective catalysts for electrocatalytic nitrogen reduction reaction (eNRR) under ambient conditions, a crucial part for the electrocatalysis system, still face large challenges of low Faradic efficiency (FE) and low yield of ammonia. Here, we propose Si‐doped BN 2D nanosheets (BNNS) as a new class of metal‐free catalysts, and computationally study their performance in eNRR by density functional theory (DFT). The calculations show that the Si atom in the boron‐edge site exhibits the highest activity with the over‐potential (η) of 1.06 V from the first hydrogenation step, which is close in value to the benchmark of this reaction, the flat Ru(0001) surface (η=0.92 V). Moreover, Si‐doping can greatly enhance the conductivity of pristine BNNS, making it a good candidate for electrocatalysis. Overall, this research opens up a new direction of designing high‐performance Si‐based 2D catalysts for dinitrogen fixation beyond the hotspot research of boron‐ or transition metal‐based catalysts.

Defective 2D silicon phosphide monolayers for the nitrogen reduction reaction: a DFT study

“…Generally, the first hydrogenation step (*N 2 + H + + e − → *N 2 H) is the potential-determining step (PDS) because the triple bond is so strong that it is very difficult to be broken by hydrogenation (ΔG *N 2 H > 1.00 eV in most cases). 11,16,30,48,69 However, in our work, the PDS is the third hydrogenation step rather than the first hydrogenation step with ΔG max = 0.87 eV along the reaction path 4 (see Fig. 6d).…”

“…For instance, experimentally available boron-containing semiconductor compounds, cubic boron phosphide (BP) and boron arsenide (BAs) with modest band gaps of 2.00 eV and 1.50 eV, respectively, theoretically exhibit very high activity and selectivity towards the ENRR; 41 exfoliated few-layer nanosheets of semiconductor black phosphorus experimentally are superior non-metal electrocatalysts for nitrogen reduction. 42 According to previous reports on Si-based NRR catalysts, 17,30,43 we know that p-block Si active sites can activate N 2 and then reduce into NH 3 under electrocatalysis conditions. Therefore, SiP monolayers have the potential of electro-reducing N 2 into NH 3 .…”

“…[24][25][26] 2D Nanomaterials have also been extensively studied in the field of the NRR due to their appealing physical and chemical properties. [27][28][29][30][31][32][33][34] However, the NRR performance of 2D nanomaterial-based catalysts is still far from being applicable. Therefore, the search for other suitable 2D materials is still underway.…”

Strategies to activate inert nitrogen molecules for efficient ammonia electrosynthesis: current status, challenges, and perspectives

“…Similar to B atoms, the Si atom with an electronegativity value of 1.9 is also promising as an electron-deficient center of metal-free carbon materials and enhance the N 2 activation process, and has drawn the attention of researchers recently regarding electrocatalytic N 2 fixation. 82 In fact, the Si element has been proved to be effective for activating some small molecules such as oxygen (O 2 ), carbon monoxide (CO), carbon dioxide (CO 2 ), etc. 83,84 As for the field of the NRR, Sun et al computationally confirmed that the Si atom of SiC can capture and activate N 2 molecules using hexagonal SiC as the model material.…”

Elemental 2D Materials: Solution‐Processed Synthesis and Applications in Electrochemical Ammonia Production

“…A recent theoretical study demonstrated that Si element (doping) is expected to exhibit a great promise for electrochemical NRR under ambient conditions. [278] Moreover, silicene, by itself, interacts very weakly with H 2 molecules. Considering all of these, exploring the feasibility of 2D silicene-based materials as potential electrocatalysts for catalytic NRR would be of great value.…”