Electrochemical NO reduction reaction (NORR) to NH₃ emerges as a fascinating approach to achieve both the migration of NO pollutant and the green synthesis of NH₃. In this contribution, within the framework of computational hydrogen model and constant-potential implicit solvent model, the NORR electrocatalyzed by a novel transition-metal-anchored SnOSe armchair nanotube (TM@SnOSe_ANT) was investigated using density functional theory calculations. Through the checking in terms of stability, activity, and selectivity, Sc- and Y@SnOSe_ANTs were screened out from the twenty-five candidates. Considering the effects of pH, solvent environment, as well as applied potential, only Sc@SnOSe_ANT is found to be most promising. The predicted surface area normalized capacitance is 11.4 μF/cm², and the highest NORR performance can be achieved at the U_RHE of −0.58 V in the acid environment. The high activity originates from the mediate adsorption strength of OH. These findings add a new perspective that the nanotube can be served as a highly promising electrocatalyst towards NORR.

Single-atom catalysts (SACs) have recently emerged as stars in boosting the synthesis of NH₃ from N₂, as the catalytic performance of the supported single atoms can be modulated by their coordination environment. In this work, we propose a new strategy, based on comprehensive density functional theory calculations, whereby the coordination environment of a single Mo atom can be tuned by a central heteroatom (X = Fe, Co, Ni, Cu, Zn, Ga, Ge, and As) in the Kegging-type polyoxometalate (POM, (XW₁₂O₄₀)ⁿ⁻) substrate to catalyze the electrochemical nitrogen reduction reactions (NRR). Firstly, we demonstrate that the single Mo atom binds strongly to the POM surface oxygen hollow sites without aggregation. Secondly, the adsorption of *N₂ on the POM-supported Mo atom is investigated and the reactivity is assessed by calculating the thermodynamics of the NRR. The results show that the POM (X = Co and As) supported Mo atom has high NRR activity with low limiting potentials. Finally, we reveal the origin of the NRR activity by analyzing the electronic structure. The results show that the charge on the O atoms of oxygen hollow sites is affected by the central heteroatom. Due to such effect, it can be found that more d electrons are transferred from Mo supported by POM (X = Co and As) to *N₂, thus the N≡N triple bond is activated. This strategy of coordination environment tuning proposed in this work provides a useful guide for the design of efficient catalysts for electrocatalysis.

On the basis of known structures of β-GeTe bulk and the derived monolayer, we proposed a series of structural analogues MXs (M = Ge, Sn; X = S, Se, Te) with an intrinsic built-in electric field via a substitution strategy. Using first-principles calculations, we demonstrated that these MX monolayers and bulks are thermodynamically, dynamically and mechanically stable, and the stabilities of bulks are more robust than the monolayer counterparts. Electronic calculations showed that the monolayers have large band gaps ranging from 2.38 to 3.27 eV while the bulks have pronounced small band gaps ranging from 0.06 to 0.78 eV. The calculated piezoelectric coefficients d₁₁ for the MX monolayers are in the range from 6.6 to 10.9 pm/V. Strikingly, the calculated d₃₃ for the MX bulks are as high as 40.3–213.7 pm/V. By correlating atomic polarizability, atomic mass, relative ion motion, Bader charge and lattice parameters, we proposed an empirical model to estimate the piezoelectric coefficients for the two-dimensional (2D) MXs, where a nice match between the estimated ones and the calculated ones was found. The versatile electronic properties and large piezoelectric coefficients endow MXs a broad prospect of application in optoelectronic and piezoelectric devices, and the revealed underlying mechanisms offer valuable guidelines for seeking novel piezoelectrics.