Nitrogen activation to ammonia via a mars-van krevelen mechanism on nitride electro-catalysts

Viable design of a green route for production of ammonia represents a cost-effective and environmental solution. One of promising alternatives to the centralized Haber-Bosch process is electroreduction of nitrogen to ammonia renewably where proton is provided by water splitting in anode and both nitrogen and electron are provided in the cathode. For the sake of decentralization, small-scale N> reduction devices are necessary Hat arc equipped with selective and active catalyst tunning well at ambient conditions without the sophistications of the Habei-Bosch piocess. Hete. we present the results of density functional theory (DFT) calculations conducted on different facets of transition metal mononitrides of Zr and V for possibility of catalytic conversion of nitrogen to ammonia under ambient conditions. The Mars-van Krevelen mechanism was studied on (100/111) facets of rocksalt and (100/110) facets of zincb ende structures. We studied the catalytic activ ity, calculated free energy of all intermediates along the reaction path for nitrogen reduction to ammonia and constructed free energy diagrams to estimate onset potential necessary for the reaction on cach dilTciciil facet. Ammonia foiilialiun was found i ioic cncigclically favoiablc on the (100) facets of rocksalt with less numbers of proton'clcctron pairs and with smaller potential-determining step (PDS) compared to other facets. Therefore, less negative potentials should be required to apply for electrochemical ammonia formation if single cr/stal (the (100) facet) of the rocksalt structure is utilized.