The electrocatalytic nitrite reduction (NO2RR) converts nitrogen-containing pollutants to high-value ammonia (NH3) under ambient conditions. However, its multiple intermediates and multielectron coupled proton transfer process lead to low activity and NH3 selectivity for the existing electrocatalysts. Herein, we synthesize a solid-solution copper-zinc cyanamide (Cu0.8Zn0.2NCN) with localized structure distortion and tailored surface electrostatic potential, allowing for the asymmetric binding of NO2-. It exhibits outstanding NO2RR performance with a Faradaic efficiency of similar to 100% and an NH3 yield of 22 mg h(-1) cm(-2), among the best for such a process. Theoretical calculations and in situ spectroscopic measurements demonstrate that Cu-Zn sites coordinated with linear polarized [NCN](2-) could transform symmetric [Cu-O-N-O-Cu] in CuNCN-NO2- to a [Cu-N-O-Zn] asymmetric configuration in Cu0.8Zn0.2NCN-NO2-, thus enhancing adsorption and bond cleavage. A paired electro-refinery with the Cu0.8Zn0.2NCN cathode reaches 2000 mA cm(-2) at 2.36 V and remains fully operational at industrial-level 400 mA cm(-2) for >140 h with a NH3 production rate of similar to 30 mg(NH3) h(-1) cm(-2). Our work opens a new avenue of tailoring surface electrostatic potentials using a solid-solution strategy for advanced electrocatalysis.

Lewis acids B(SiR3)3 and B(GeR3)3 form anomalously strong complexes with Lewis bases N2 and CO. Intramolecular B−N/C bonds are generally in the range 1.45–1.50 Å and shorter than the sum of B and N/C covalent radii. Bonding analyses have shown that the strong bonds are a consequence of a novel σ-donation and π-backdonation mechanism, where electrons are donated into an empty sp3-type orbital on B (LUMO) from the σ-orbitals of N2/CO and electrons are backdonated from the B−Si/Ge σ-bonds into the π-type orbitals of N2/CO. Here we have analyzed the complexes between Lewis acids B(SiH3)3 and B(CF3)3 and Lewis bases N2, CO and NH3 using the extended transition state – natural orbitals for chemical valence (ETS-NOCV) method. Both σ-donation and π-backdonation are present in all complexes, and deformation densities due to the two mechanisms, i. e. NOCV pair densities, are surprisingly similar in character. Energy stabilization due to π-backdonation is much larger for the complexes of B(SiH3)3 with N2 and CO, and σ-donation stabilization is also enhanced compared to the corresponding complexes of B(CF3)3. Differential electrostatic potential indicate that the enhanced stabilization of the B(SiH3)3 complexes is largely an effect of reduced charge separation due to the balance between σ-donation and π-backdonation.

The electrocatalytic nitrate reduction (NO3RR) holds significance in both NH3 synthesis and nitrate contamination remediation. However, achieving industrial-scale current and high stability in membrane electrode assembly (MEA) electrolyzer remains challenging due to inherent high full-cell voltage for sluggish NO3RR and water oxidation. Here, Cu2NCN with positive surface electrostatic potential VS(r) is applied as highly efficient NO3RR electrocatalysts to achieve industrial-current and low-voltage stable NH3 production in MEA electrolyzer with coupled anodic glycerol oxidation. This paired electro-refinery (PER) system reaches 4000 mA cm−2 at 2.52 V and remains stable at industrial-level 1000 mA cm−2 for 100 h with the NH3 production rate of 97000 µgNH3 h−1 cm−2 and a Faradaic efficiency of 83%. Theoretical calculations elucidate that the asymmetric and electron-withdrawing [N−C≡N] units enhance polarization and VS(r), promoting robust and asymmetric adsorption of NO3* on Cu2NCN to facilitate O−N bond dissociation. A comprehensive techno-economic analysis demonstrates the profitability and commercial viability of this coupled system. Our work opens a new avenue and marks a significant advancement in MEA systems for industrial NH3 synthesis.

In this paper, we focus on surface electrostatic potentials and a variety of statistically derived quantities defined in terms of the surface potentials. These have been shown earlier to be meaningful in describing features of these potentials and have been utilized to understand the interactive tendencies of molecules in condensed phases. Our current emphasis is on ionic salts and liquids instead of neutral molecules. Earlier work on ionic salts has been reviewed. Presently, our results are for a variety of singly charged cations and anions that can combine to form ionic solids or liquids. Our approach is computational, using the density functional B3PW91/6-31G(d,p) procedure for all calculations. We find consistently that the average positive and negative surface electrostatic potentials of the cations and anions decrease with the size of the ion, as has been noted earlier. A model using computed statistical quantities has allowed us to put the melting points of both ionic solids and liquids together, covering a range from 993 °C to 11 °C.

Development of an efficient electrocatalyst for the nitrogen reduction reaction (NRR) to serve as a sustainable alternative to the Haber-Bosch process has proven highly challenging. Single atom catalysts (SACs), which have the maximum atom utilization efficiency, are among the most promising candidates. Single atoms can be incorporated to a catalytic system by doping or substitution or by attaching a molecular coordination complex to a substrate and the different insertion modes allow the chemical environment to be varied. We have used DFT to investigate vanadium SACS for NRR activity with a focus on varying the coordination environment of the V atom. Phthalocyanine, porphyrin and graphene like coordination environments with varying N-coordination have been studied. Vanadium phthalocyanine (V_phN₄) is the most promising of the investigated systems. It features high selectivity relative the HER reaction and relatively strong binding of N₂ relatively H, which prevents poisoning of the surface by hydrogen. V_phN₄ also has the lowest overpotential among the studied systems. The electrocatalytic properties of V_phN₄ deposited as a monolayer on the Ag (111) surface have been investigated. This system, which already has been prepared, shows promising properties for use as a catalytic electrode for the NRR reaction

Dearomatizations provide powerful synthetic routes to rapidly assemble substituted carbocycles and heterocycles found in a plethora of bioactive molecules. Harnessing the advantages of dearomatization typically requires vigorous reagents because of the difficulty in disrupting the stable aromatic core. A relatively mild dearomatization strategy is described that employs lithiated nitriles or isocyanides in a simple S<inf>N</inf>Ar-type addition to form σ-complexes that are trapped by alkylation. The dearomatizations are diastereoselective and efficient and rapidly install two new carbon-carbon bonds, one of which is a quaternary center, as well as nitrile, isocyanide, and cyclohexadiene functionalities.

Enzymes in nature efficiently catalyze chiral organic molecules by elaborately tuning the geometrical arrangement of atoms in the active site. However, enantioselective oxidation of organic molecules by heterogeneous electrocatalysts is challenging because of the difficulty in controlling the asymmetric structures of the active sites on the electrodes. Here, we show that the distribution of chiral kink atoms on high-index facets can be precisely manipulated even on single gold nanoparticles; and this enabled stereoselective oxidation of hydroxyl groups on various sugar molecules. We characterized the crystallographic orientation and the density of kink atoms and investigated their specific interactions with the glucose molecule due to the geometrical structure and surface electrostatic potential.

Multi-active sites and electron configurations of boron-based bi-atom catalysts doped in silicene monolayers optimize adsorption behavior and facilitate the C–C coupling process for enhancement of CO reduction towards ethanol..

The electrochemical CO reduction reaction (CORR) is faced by challenges in achieving high-value-added C 2 products due to inefficient C–C bond formation and low selectivity. Using first-principles calculations, we propose a framework for boron-based bi-atom doping into a silicene monolayer (B–X@Si) to improve CORR catalytic efficiency. Transition metal (TM)-free B–B@Si and TM-containing B–Cu@Si serve as efficient bi-atom catalysts (BACs) with low limiting potentials (−0.28 and −0.63 V) and low activation barriers for C–C coupling (0.54 and 0.53 eV). The CO* binding strength of active sites with co-adsorbed CO* species follows the order TM < B < B–TM. Remarkably, the interplay within the B–TM pair strengthens CO* adsorption, driven by increased TM involvement, as characterized by the upward shift of the d-band center of TM in B–TM@Si relative to Fermi level. The coupling kinetics depend on the reactivity of C(CHO*) and CO* fragments within the decoupled CHO–CO* intermediate. Intriguingly, hetero-B–TM@Si systems display a trade-off between stronger CHO* and weaker CO* binding compared to the moderate binding observed in homo-B–B@Si. Among the TMs, Cu appears the most appropriate partner with B; the moderate synergistic effect of the B–Cu pair resulting in the smallest augmented C-affinity (CHO*) is offset by the weakest CO* binding strength on Cu itself, ensuring rapid C–C coupling similar to that of B–B@Si. Our BACs offer unique multi-functional active sites due to participation of host atoms (Si*) adjacent to the bi-dopants; these Si-atoms stabilize adsorbates, facilitate the subsequent C–C coupling step, and protect the C–O bond for selective ethanol production. This study provides theoretical insights for the development of advanced BACs with novel multi-adsorbing sites and tailored charge redistribution that enhance CO-to-C 2 conversion.

Chemical transformations of molecular nitrogen (N2), including the nitrogen reduction reaction (NRR), are difficult to catalyze because of the weak Lewis basicity of N2. In this study, it is shown that Lewis acids of the types B(SiR3)3 and B(GeR3)3 bind N2 and CO with anomalously short and strong B-N or B-C bonds. B(SiH3)3·N2 has a B-N bond length of 1.48 Å and a complexation enthalpy of −15.9 kcal mol−1 at the M06-2X/jun-cc-pVTZ level. The selective binding enhancement of N2 and CO is due to π-backbonding from Lewis acid to Lewis base, as demonstrated by orbital analysis and density difference plots. The π-backbonding is found to be a consequence of constructive orbital interactions between the diffuse and highly polarizable B-Si and B-Ge bond regions and the π and π* orbitals of N2. This interaction is strengthened by electron donating substituents on Si or Ge. The π-backbonding interaction is predicted to activate N2 for chemical transformation and reduction, as it decreases the electron density and increases the length of the N-N bond. The binding of N2 and CO by the B(SiR3)3 and B(GeR3)3 types of Lewis acids also has a strong σ-bonding contribution. The relatively high σ-bond strength is connected to the highly positive surface electrostatic potential [VS(r)] above the B atom in the tetragonal binding conformation, but the σ-bonding also has a significant coordinate covalent (dative) contribution. Electron withdrawing substituents increase the potential and the σ-bond strength, but favor the binding of regular Lewis acids, such as NH3 and F−, more strongly than binding of N2 and CO. Molecules of the types B(SiR3)3 and B(GeR3)3 are chemically labile and difficult to synthesize. Heterogenous catalysts with the wanted B(Si-)3 or B(Ge-)3 bonding motif may be prepared by boron doping of nanostructured silicon or germanium compounds. B-doped and hydrogenated silicene is found to have promising properties as catalyst for the electrochemical NRR.

The aromatic hydrocarbons (AHs) fluorobenzene, naphthalene, and 1-fluoronaphthalene are introduced as promising alternatives to xenon as propellant for in-space electric propulsion (EP). These storable molecules have similar mass, lower cost, and lower ionization energies compared to xenon, as well as the critical advantage of low post-ionization fragmentation compared to other molecular propellant candidates. The ionization characteristics of AHs are compared with those of xenon and the diamondoid adamantane, previously evaluated as a molecular propellant for EP. Quantum chemical calculations and BEB theory together with 25 eV electron ionization mass spectrometry (EI-MS) measurements have been used to predict the fragmentation of the AHs and adamantane when ionized in a plasma with an electron temperature of 7 eV (a typical electron temperature in EP plasmas). A high fraction (81 − 86%) of the detected AH ions originate from intact molecules, compared to 34% for adamantane, indicating extraordinarily low fragmentation for the selected AHs. The ionization potential of the AHs is similar to that of adamantane but lower compared to xenon (8.14–9.2 eV for the AHs, 9.25 for adamantane and 12.13 eV for xenon). BEB calculations have also been used to predict total ionization cross sections. The calculated ionization cross section of the AHs is comparable to that of adamantane but 3–5 times higher than that of xenon, which together with the low ionization potential can contribute to more efficient ionization. The AHs may have the potential to perform better than xenon, despite the absence of fragmentation in xenon.