Antiferromagnetic semiconductor in porous boron nitride (B6N6) sheet: First-principles investigation

Structural Design of π-d Conjugated TMx B3 N3 S6 (x=2, 3) Monolayer Toward Electrocatalytic Ammonia Synthesis

Single-atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π-d conjugated TMx B3 N3 S6 (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM2 B3 N3 S6 and III-TM3 B3 N3 S6 are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM2 B3 N3 S6 and 4-coordinated III-TM3 B3 N3 S6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B3 N3 S6 ligand is an ideal support for TM atoms due to existence of strong TM-S bonds. The 3-coordinated I-V2 B3 N3 S6 is the best SAC with the low limiting potential (UL ) of -0.01 V, excellent stability (Ef =-0.32 eV, Udiss =0.02 V) and remarkable selectivity characteristics. This work not only provides novel π-d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis.

The novel π-d conjugated TM2B3N3S6 (TM = Mo, Ti and W) monolayers as highly active single-atom catalysts for electrocatalytic synthesis of ammonia

Recently, single-atom catalysts (SACs) are receiving significant attention in electrocatalysis fields due to their excellent specific activities and extremely high atomic utilization ratio. Effective loading of metal atoms and high stability of SACs increase the number of exposed active sites, thus significantly improving their catalytic efficiency. Herein, we proposed a series (29 in total) of two-dimensional (2D) conjugated structures of TM2B3N3S6 (TM means those 3d to 5d transition metals) and studied the performance as single-atom catalysts for nitrogen reduction reaction (NRR) using density functional theory (DFT). Results show that TM2B3N3S6 (TM = Mo, Ti and W) monolayers have superior performance for ammonia synthesis with low limiting potentials of -0.38, -0.53 and -0.68 V, respectively. Among them, the Mo2B3N3S6 monolayer shows the best catalytic performance of NRR. Meanwhile, the π conjugated B3N3S6 rings undergo coordinated electron transfer with the d orbitals of TM to exhibit good chargeability, and these TM2B3N3S6 monolayers activate isolated N2 according to the "acceptance-donation" mechanism. We have also verified the good stability (i.e., Ef < 0, and Udiss > 0) and high selectivity (Ud = -0.03, 0.01 and 0.10 V, respectively) of the above four types of monolayers for NRR over hydrogen evolution reaction (HER). The NRR activities have been clarified by multiple-level descriptors (ΔG*N2H, ICOHP, and Ɛd) in the terms of basic characteristics, electronic property, and energy. Moreover, the aqueous solution can promote the NRR process, leading to the reduction of ΔGPDS from 0.38 eV to 0.27 eV for the Mo2B3N3S6 monolayer. However, the TM2B3N3S6 (TM = Mo, Ti and W) also showed excellent stability in aqueous phase. This study proves that the π-d conjugated monolayers of TM2B3N3S6 (TM = Mo, Ti and W) as electrocatalysts show great potentials for the nitrogen reduction.

Novel Two-Dimensional Metal-Based π-d Conjugated Nanosheets as Photocatalyst for Nitrogen Reduction Reaction: The First-Principle Investigation

Photocatalytic nitrogen reduction reaction (NRR) is becoming a promising route for producing green and sustainable ammonia under ambient conditions. However, the development of highly efficient photocatalysts for NRR still remains a grand challenge as a result of the sluggish activation of inert N₂, the competitive hydrogen evolution reaction (HER), and inadequate photogenerated external potential, which usually cause extremely poor NRR performance and low light utilization efficiency. Herein, on the basis of density functional theory (DFT) computations, we rationally designed a series of two-dimensional (2D) π-d conjugated metal-B₃N₃ (M₃B₆N₆S₁₂) semiconductors. Using the electron "σ acceptance-π* backdonation" process, Mo₃B₆N₆S₁₂ and Nb₃B₆N₆S₁₂ can efficiently activate and reduce N₂ to ammonia with a rather low overpotential of 0.07 and 0.21 V, respectively. Importantly, a high photogenerated external potential enables spontaneous NRR on Mo₃B₆N₆S₁₂ and Nb₃B₆N₆S₁₂ under visible/infrared light irradiation, contributing to the extraordinary photoactivity of Mo₃B₆N₆S₁₂ and Nb₃B₆N₆S₁₂ as promising solar light-driven N₂ fixation catalysts. Meanwhile, the competing HER is effectively restrained. For the first time, we rationally propose a series of M₃B₆N₆S₁₂ semiconductors as promising metal-based photocatalysts for N₂ reduction with extraordinary photoactivity and a high photogenerated external potential. This work paves a new path for the rational designing of 2D metal-based NRR photocatalysts with high activity, good selectivity, and high stability.