Vanadium oxynitride and other earth-abundant oxynitrides are of growing interest for the electrocatalytic reduction of nitrogen to NH 3 . A major unresolved issue, however, concerns the roles of lattice N and lattice O in this process. Electrochemistry and photoemission data reported here demonstrate that both lattice N and dissolved N 2 are reduced to NH 3 by cathodic polarization of vanadium oxynitride films at pH 7. These data also show that ammonia production from lattice N occurs in the presence or absence of N 2 and involves the formation of VN: intermediates or similar unsaturated VN surface states on a thin vanadium oxide overlayer. In contrast, N 2 reduction proceeds in the presence or absence of lattice N and without N incorporation into a vanadium oxide lattice. Thus, both lattice N and N 2 reduction mechanisms involve oxide-supported V surface sites ([V] O ) in preference to Nsupported sites ([V] N ). This result is supported by density functional theory-based calculations showing that the formation of V N:, V−NN−H, and a few other plausible reaction intermediates is consistently energetically favored at [V] O rather than at [V] N surface sites. Similar effects are predicted for the oxynitrides of other oxophilic metals, such as Ti.

The electrocatalytic nitrogen reduction reaction (NRR) is of significant interest as an environmentally friendly method for NH3 production for agricultural and clean energy applications. Selectivity of NRR vis-à-vis the hydrogen...

The electrocatalytic reduction of molecular nitrogen to ammonia—the nitrogen reduction reaction (NRR)—is of broad interest as an environmentally- and energy-friendly alternative to the Haber-Bosch process for agricultural and emerging energy applications. Herein, we review our recent findings from collaborative electrochemistry/surface science/theoretical studies that counter several commonly held assumptions regarding transition metal oxynitrides and oxides as NRR catalysts. Specifically, we find that for the vanadium oxide, vanadium oxynitride, and cobalt oxynitride systems, (a) there is no Mars-van Krevelen mechanism and that the reduction of lattice nitrogen and N2 to NH3 occurs by parallel reaction mechanisms at O-ligated metal sites without incorporation of N into the oxide lattice; and (b) that NRR and the hydrogen evolution reaction (HER) do occur in concert under the conditions studied for Co oxynitride, but not for V oxynitride. Additionally, these results highlight the importance of both O-ligation of the V or Co center for metal-binding of dinitrogen, and the importance of N in stabilizing the transition metal cation in an intermediate oxidation state, for effective N≡N bond activation. This review also highlights the importance and limitations of ex situ and in situ photoemission—involving controlled transfer between UHV and electrochemistry environments, and of operando Near Ambient Pressure photoemission coupled with in situ studies, in elucidating the complex chemistry relevant to the electrolyte/solid interface.

Cooperative enamine‐metal Lewis acid catalysis has emerged as a powerful tool to construct carbon‐carbon and carbon‐heteroatom bond forming reactions. A concise synthetic method for asymmetric synthesis of chromans from cyclohexanones and salicylaldehydes has been developed to afford tricyclic chromans containing three consecutive stereogenic centers in good yields (up to 87 %) and stereoselectivity (up to 99 % ee and 11 : 1 : 1 dr). This difficult organic transformation was achieved through bifunctional enamine‐metal Lewis acid catalysis. It is believed that the strong activation of the salicylaldehydes through chelating to the metal Lewis acid and the bifunctional nature of the catalyst accounts for the high yields and enantioselectivity of the reaction. The absolute configurations of the chroman products were established through X‐ray crystallography. DFT calculations were conducted to understand the mechanism and stereoselectivity of this reaction.