| Popis: |
Standard enthalpies and entropies of formation of many metal nitrides (MN) were measured in 60s, 70s and 80s of the last century. We have used this available thermochemical data and made a unique analysis in the NH3 electrocatalysis field. Briefly, we have calculated M→MN and MN→NH3 standard cell potentials for 36 metal nitrides. We found that potentials needed to start the onset for nitrogen reduction reaction (NRR), earlier calculated using density functional theory, scale linearly with the cell potentials we calculated. We have used the linear relations as “calibration curves” and from known cell potentials calculated NRR onset potentials for all elements analysed. This allowed us to build a large Volcano plot for NRR. We found that: i) transition metal Mn is the most reactive catalyst; ii) there is a gap of unidentified materials close to the top of the Volcano plot; and iii) posttransition metals, Ga and In, are close to the top. We have calculated the potentials needed to start the onset for HER and NRR at different pH and we have identified new, overlooked metal catalysts which might selectively catalyse NRR at pH>4. |
