Electrochemical and Chemical Instability of Vanadium Nitride in the Synthesis of Ammonia Directly from Nitrogen

Abstract

Recently, vanadium nitride (VN) was proposed as an active catalyst for a challenging electrochemical nitrogen reduction reaction (NRR) to ammonia. In this study, the stability of vanadium‐nitride in electrolyte solutions of different pH values was studied under selected cathodic potentials. Intensive leaching of vanadium ions and nitrogen constituents into the bulk of the electrolyte solution was confirmed from ICP‐OES and UV‐Vis results.

Major Improvement in the Cycling Ability of Pseudocapacitive Vanadium Nitride Films for Micro‐Supercapacitor

“…Three broad bands with low intensities (≈234, 379, and 842 cm −1 ) are pointed out with spectra similar to already published ones for VN films or VN slurry prepared by magnetron sputtering method or solution processing route respectively. [ 50,51 ] The Raman spectra acquired on the same samples (orange curve) after 10 months revealed the presence of a set of well‐defined peaks (at 146, 262, 320, 411, 500, 690, and 990 cm −1 , respectively) which could be ascribed to the presence of a surface oxide layer on VN [ 52 ] corresponding to the progressive oxidation of sputtered VN films. Regarding the literature, [ 53 ] this surface oxide layer could probably correspond to an amorphous V 2 O 5 film or a poorly crystallized α‐V 2 O 5 .…”

Vanadium oxynitrides as stable catalysts for electrochemical reduction of nitrogen to ammonia: the role of oxygen

“…Existing theoretical work 21,29,30 has focused on the N 2 RR mechanism on nitride surfaces, and have not studied the atomistic mechanism, thermodynamic limitations on oxynitrides in details. For example, vanadium nitride, which has been investigated theoretically 29 , does not display good long term stability [31][32][33] in the N 2 RR electrochemical environment as nitrogen and vanadium leach into typical electrolyte solutions, thus limiting its application in ammonia electro-synthesis through N 2 RR. In fact, some experiments indicate that pure nitrides might actually be just decomposing towards ammonia evolution 32,34 , and recent spectroscopic characterization identifies that pure vanadium nitride is inactive for N 2 RR 22,34 , while oxynitride variety shows good activity 22,26 .…”

Assessing the Activity Trend of Metal Nitride Catalysts for Ammonia Synthesis Based on Theory of Chemical Potential Kinetics

“…[3c,e,7,16] What is noteworthy here is that there are some results pointing out the propensity of NbN and VN to release lattice nitrogen atoms in electrochemical reduction of N 2 to ammonia. [4,17] Therefore, we further studied the probability that the surface N vacancy can migrate to the bulk of MNs to assess the stability from a thermochemical perspective. We find that NbN and VN are less stable than CeN and LaN (see Figure S3).…”

“…Thereinto, metal nitrides (MNs) have attracted considerable attentions, [3] due to their high mechanical strength, excellent conductivity, chemical resistance and the diversity of compound in this class of material that can be synthesized [4] . Previously, Co 3 Mo 3 N and a series of ternary nitrides of the similar type were reported to have high catalytic activity [5] .…”

“…Thereinto, metal nitrides (MNs) have attracted considerable attentions, [3] due to their high mechanical strength, excellent conductivity, chemical resistance and the diversity of compound in this class of material that can be synthesized. [4] Previously, Co 3 Mo 3 N and a series of ternary nitrides of the similar type were reported to have high catalytic activity. [5] Hunter et al [6] demonstrated the possibility of the Mars-van Krevelen (MvK) mechanism in ammonia synthesis through the nitrogen isotopic exchange experiments over Co 3 Mo 3 N. Recently the pioneering work were carried out by Ye et al that the Ni/LaN and Ni/CeN catalysts with high activities for ammonia synthesis can be achieved at 400 °C and atmospheric pressure via the MvK mechanism.…”