Designing earth‐abundant element based efficient and durable electrocatalysts for hydrogen evolution reaction (HER) is attracting growing attention as the renewable electricity supply sector urgently needs sustainable methods for storing energy. Nitrogen functionalized carbon nanomaterials are an interesting electrocatalysts option because of their attractive electrical properties, excellent chemical stability and catalytic activity. Hence, this study reports the HER mechanism on nitrogen functionalized few‐walled carbon nanotubes (N‐FWCNT). With this earth‐abundant element based catalyst 250 mV overpotential is required to reach 10 mA cm−2 current density and so its HER activity is comparable to other non‐noble metal catalysts, and clearly among the highest previously reported for N‐FWCNTs. To gain fundament insight on their functioning, computational analysis has been carried out to verify the effect of nitrogen and to analyze the reaction mechanism. The reaction mechanism has also been analyzed experimentally with a pH series, and both the methods suggest that the HER proceeds via the Volmer‐Heyrovský mechanism. Overall hydrogen surface coverage on N‐FWCNT is also suggested to affect the HER rate. Interestingly, in the studied structure, carbons in vicinity of nitrogen atoms, but not directly bound to nitrogen, appear to promote the HER most actively. Furthermore, durability of N‐FWCNTs has been demonstrated by operating a full electrolyzer cell for five weeks.

The cyclocondensation reaction of equimolar amounts of SeCl2 and (Me3Si)2NMe in THF affords 1,3,5,7-Se4(NMe)4 (5b) [δ((77)Se) = 1585 ppm] in excellent yield. An X-ray structural determination showed that 5b consists of cyclic, puckered crown-shaped molecules with a mean Se-N bond length of 1.841 Å typical of single bonds. A minor product of this reaction was isolated as unstable orange-red crystals, which were identified by X-ray analysis as the adduct 1,5-Se6(NMe)2·(1)/2Se8 (1b·(1)/2Se8), composed of cyclic 1,5-Se6(NMe)2 and disordered cyclo-Se8 molecules. A detailed reinvestigation of the cyclocondensation reaction of SeCl2 and (t)BuNH2 as a function of molar ratio and time by multinuclear ((1)H, (13)C, and (77)Se) NMR spectroscopy revealed that the final product exhibits one (77)Se resonance at 1486 ppm and equivalent N(t)Bu groups. The shielding tensors of 28 selenium-containing molecules, for which the (77)Se chemical shifts are unambiguously known, were calculated at the PBE0/def2-TZVPP level of theory to assist the spectral assignment of new cyclic selenium imides. The good agreement between the observed and calculated chemical shifts enabled the assignment of the resonance at 1486 ppm to 1,3,5,7-Se4(N(t)Bu)4 (5a). Those at 1028 and 399 ppm (intensity ratio 2:1) could be attributed to 1,5-Se6(NMe)2 (1b).

The third member of the series of imidoselenium(II) chlorides ClSe[N(tBu)Se]nCl (n = 3) (9) has been isolated from the cyclocondensation reaction of tBuNH2 and SeCl2 in THF in a molar ratio of ca. 3:1 and characterized in the form of two polymorphs 9a and 9b by single crystal X-ray analysis. The unusual structural features of this nine-atom chain are explained satisfactorily in terms of a bonding model that invokes intra-molecular secondary bonding interactions and hyperconjugation. The reaction of the bifunctional reagent ClSe[N(tBu)Se]2Cl (8) with tBuNH2 in THF occurs via concurrent pathways to give 1,3,5-Se3(NtBu)3 (1) and 1,3-Se3(NtBu)2 (3a). The energetics of the reactions of tBuNH2 and SeCl2 in THF have been calculated at the PBE0/def2-TZVPP level of theory in order to assess the feasibility of ClSe[N(tBu)Se]nCl (7–9, n = 1–3) as intermediates in the formation of known cyclic selenium imides. DFT calculations were also employed to explore the energy profile of the pathway of the formation of the first member of the series ClSeN(tBu)SeCl (7) from tBuNH2 and SeCl2 in THF at 298 K. The neutral ligand ClSeN(tBu)SeCl (7) is Se,Se′-coordinated to the metal centre in the unusual adduct [PdCl2{Se,Se′-(SeCl)2N(tBu)}]·[PdCl2{Se,Se′-Se4(NtBu)3}]·MeCN (10·MeCN), which is the first metal complex of an imidoselenium(II) chloride.

Platinum (Pt)-free catalysts for the hydrogen evolution reaction (HER) is currently a blooming research topic in view of the high cost and scarcity of Pt. Experiments on single-shell carbon-encapsulated iron nanoparticles (SCEINs) have proven comparable HER catalytic efficiency with the best Pt catalyst. However, an understanding of the structure-toefficiency is missing. We performed ab initio density functional theory calculations on a realistic model of SCEINs, namely Fe 55 @C 240 , to shed light on the catalytic properties of SCEINs and studied C 60 and C 240 fullerenes for comparison. Both the thermodynamic free energy approach (ΔG H ) and kinetic (Volmer−Heyrovsky/Tafel reaction barrier E a ) calculations were realized on these systems. Our calculations proved that Fe 55 has a key role in enhancing the hydrogen binding on C 240 . Volmer−Heyrovskýis the preferred mechanism, Heyrovskýbeing the limiting reaction with E a > 1 eV. Non-zero coverage of the carbon surface enhances ΔG H without significantly affecting E a . Because the ΔG H -to-E a relationship is nonlinear, we proposed a computationally efficient strategy based on the DDEC6 bond order (BO) method to preselect potential HER sites before any calculations. E a proved to be highly site-and (C−Fe) BO-dependent, leading to the highly heterogeneous catalytic ability of Fe 55 @C 240 . ΔG H /E a best pairs can then be optimized by playing with the surface coverage.

Reductive debromination of the tribromoamidosilane 2 gave the tetracyclic silaheterocycle 3 through a unique reaction cascade involving unprecedented two-fold intramolecular cycloaddition by transient silylenes. Experimental and computational analyses of the...