Redox‐Mediated Ambient Electrolytic Nitrogen Reduction for Hydrazine and Ammonia Generation

Abstract

This work presents a redox‐mediated electrolytic nitrogen reduction reaction (RM‐eNRR) using polyoxometalate (POM) as the electron and proton carrier which frees the TiO2‐based catalyst from the electrode and shifts the reduction of nitrogen to a reactor tank. The RM‐eNRR process has achieved an ammonium production yield of 25.1 μg h−1 or 5.0 μg h−1 cm−2 at an ammonium concentration of 6.7 ppm. With high catalyst loading, 61.0 ppm ammonium was accumulated in the electrolyte upon continuous operation, which is the highest concentration detected for ambient eNRR so far. The mechanism underlying the RM‐eNRR was scrutinized both experimentally and computationally to delineate the POM‐mediated charge transfer and hydrogenation process of nitrogen molecule on the catalyst. RM‐eNRR is expected to provide an implementable solution to overcome the limitations in the conventional eNRR process.

Progress of Experimental and Computational Catalyst Design for Electrochemical Nitrogen Fixation

“…∼−0.40 150 NiSb, 148 NiPc, 149 NiO@TiO 2 , 150 Ni-BCN 151 10. 75 129,162,164,165 ∼30 161 −0.05 165 ∼−0.80 166 Rh/GDY, 129 Y-TiO 2 -C, 161 BP@SnO 2−x , 162 Te-C, 163 Ag/TiO 2 , 164 SnO 2 /NC, 165 Sn/SnS 2 , 166 SnS 2 @Ni, 167 Y 1 /NC, 168 C@YSZ, 169 Te/SeO 170 Iso-eSi x , 178 F/PC, 179 Cl-GDY, 180 CNS 181 h-BNNS, 182 PNG, 183 LiN 2 /Mo, 31 LiNR, 37 Li-SICON, 38 LiCl, 39 HBTCu 40 150−200 atm are applied to ensure the favorable reaction equilibrium toward the NH 3 products. Thus, high temperature and pressure are needed to guarantee a significant turnover frequency (TOF, Figure 2B).…”

Development of Carbon‐Based Electrocatalysts for Ambient Nitrogen Reduction Reaction: Challenges and Perspectives

“…In 10 M LiCl, the Faradic efficiency is 71 � 1.9 % and the ammonia yield at À 0.3 V (compared with reversible hydrogen electrode) is (9.5 � 0.4) × 10 À 10 mol s À 1 cm À 2 . Additionally, Wang et al [73] used polyoxometalate (POM) as an electron and proton carrier and released FeÀ TiO 2 catalyst onto electrodes. Meanwhile, nitrogen reduction was transferred to a reaction container.…”

Across the Board: Gabriele Centi on Decoupling Electrocatalytic Reactions to Electrify Chemical Production

“…This decoupling of anodic and cathodic reaction is a current frontier of research, although with focus on water electrolysis [6–13] . However, the spatiotemporal decoupling could be applied also to (i) PEC devices, [6,14] leading to interesting solar‐to‐hydrogen conversion efficiency of 7.5 %, and (ii) other reactions than water electrolysis, such as direct conversion of N 2 to ammonia [15] . This is perhaps the most exciting direction to develop novel solutions for solar‐to‐energy vectors production in remote areas, to enable an effective renewable‐energy based society.…”

“…[ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] However, the spatiotemporal decoupling could be applied also to (i) PEC devices,[ 6 , 14 ] leading to interesting solar‐to‐hydrogen conversion efficiency of 7.5 %, and (ii) other reactions than water electrolysis, such as direct conversion of N 2 to ammonia. [15] This is perhaps the most exciting direction to develop novel solutions for solar‐to‐energy vectors production in remote areas, to enable an effective renewable‐energy based society. The use of redox mediators allows not only spatiotemporal decoupling of anodic and cathodic reactions, but also brings about a series of additional potential benefits, such as better kinetics (e. g., with respect to oxygen evolution) and reduction of the overpotential, safety and operational flexibility, and not least a potential better control of competitive paths in reactions such as CO 2 or N 2 reduction.…”