Electrochemical synthesis of ammonia using a proton conducting solid electrolyte and nickel cermet electrode

Abstract

Electrochemical synthesis of ammonia (NH 3 ) using a proton conducting solid electrolyte and nickel (Ni) cermet electrodes has been studied. As an electrolyte, BaCe 0.9 Y 0.1 O 3¹¤ (BCY) perovskite-type oxide was prepared by a co-precipitation method and its electrolyte pellet was synthesized by the sintering method with small amount of nickel oxide (NiO) as a sintering aid. The NiBCY cermet was employed as electrodes of anode and cathode. To evaluate the performance of this cell, electrochemical synthesis of NH 3 from dry nitrogen (N 2 ) and wet hydrogen (H 2 ) was conducted at 500°C. As a result, the maximum formation rate of NH 3 was 3.36 © 10 ¹10 mol s ¹1 cm ¹2 at the applied voltage of ¹0.2 V against open circuit voltage using the NiBCY«BCY(NiO)«NiBCY cell, and the Faradic efficiency was 0.63%. Durability test of NH 3 electrochemical synthesis from dry N 2 and wet H 2 revealed that current density of cell was relatively stable for 15 h but NH 3 formation rate was decreased slightly. In addition, using NiBCY based cell, NH 3 was successfully synthesized from dry N 2 and steam diluted argon with the applied voltage of ¹1.8 V at a rate of 2.79 © 10 ¹10 mol s ¹1 cm ¹2 and the Faradic efficiency was 0.15%. And this fabricated cell kept the high NH 3 formation rate during the long-term test at ¹2.0 V for 15 h.

Electrochemical Ammonia Generation Directly from Nitrogen and Air Using an Iron-Oxide/Titania-Based Catalyst at Ambient Conditions

“…As the applied potential increased from −0.577 to −0.777 V, both the rate of ammonia formation and FE declined and finally reached a value of 1.88 × 10 –10 mol mg –1 s –1 and 0.03%, respectively. This illustrates the competition between NRR and HER predominantly at high potentials, giving rise to low FEs observed at potentials below −0.377 V. The obtained results are comparable with both iron-based (nano-Fe 2 O 3 , γ-Fe 2 O 3 , nano-Fe 3 O 4 , and CoFe 2 O 4 ) ,,− and non-iron-based catalysts (Ru/Cs + /MgO and BaCe 0.9 Y 0.1 O 3−δ ), , which were reported earlier for the systems that operate at relatively high temperatures (as shown in Table T1 in the Supporting Information).…”

Recent Advances and Challenges of Electrocatalytic N2Reduction to Ammonia

“…However, this design is possibly responsible for the low ammonia formation rates (≤3.0 × 10 –13 mol s –1 cm –2 ) observed in both types of electrochemical cells; more specifically, the hydrogen species (protons or hydrogen atoms) combined on the metal surface to form H 2 rather than reaching the Ru surface to produce ammonia. Other proton conductors that have been used as electrolytes in electrochemical cells for ammonia synthesis include BaCe 0.9 Y 0.1 O 3−δ and BaZr 0.8 Y 0.2 O 3−δ , and the N 2 reduction catalysts employed include Ni-BaCe 0.9 Y 0.1 O 3−δ , La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ , Ag, and Pt . In addition, the group of Tao performed a series of ammonia synthesis experiments using oxide–carbonate electrolytes and complex metal oxide electrocatalysts, in both double-chamber − and single-chamber − electrolysis cells.…”

Vanadium Nitride Is an Efficient Hydrogen-Diffusive Cathode for Green Ammonia Electrochemical Synthesis by Protonic Solid Oxide Electrolysis Cells

“…However, the performances of H 2 O–N 2 coelectrolytic H + -SOCs have been limited in terms of NH 3 yields and evolution rates, typically less than 1% and 10 –11 mol cm –2 s –1 , respectively. − The main challenge lies in the absence of suitable cathode materials for the electrochemical nitrogen reduction reaction (ENRR), represented by the equation N 2 + 8H + + 6e – → 2NH 3 . The competing hydrogen evolution reaction (HER), with lower or similar redox overpotential compared to N 2 (ENRR: 0.092 V vs RHE, HER: 0.00 V vs RHE), exacerbates the situation.…”