Ammonia synthesis using Fe/BZY–RuO₂ catalysts and a caesium dihydrogen phosphate-based electrolyte at intermediate temperatures

Abstract

We developed an Fe2O3/BZY (yttrium-doped barium zirconate)–RuO2 (Fe/BZY–RuO2) cathode catalyst, which was applied to the electrochemical synthesis of NH3 using a proton-conducting electrolyte, CsH2PO4/SiP2O7, at 220 °C and ambient pressure.

Fe‐based catalysts for nitrogen reduction toward ammonia electrosynthesis under ambient conditions

“…(C) Production rate and corresponding FE of NH 3 and N 2 H 4 . Reproduced with permission 118 . Copyright 2021, Royal Society of Chemistry.…”

“…The excellent NRR performance contributes to the synergistic effect of Fe 3 O 4 's strong N 2 fixation ability and Au's charge transfer capability. Kikuchi et al 118 . reported a Fe 2 O 3 /yttrium‐doped barium zirconate–RuO 2 (Fe/BZY–RuO 2 ) cathode catalyst.…”

An in situ DRIFTS study on nitrogen electrochemical reduction over an Fe/BaZr0.8Y0.2O3−δ-Ru catalyst at 220 °C in an electrolysis cell using a CsH2PO4/SiP2O7 electrolyte

“… 3 In our previous work on electrochemical NH 3 synthesis using an Fe/BZY-RuO 2 catalyst and CsH 2 PO 4 /SiP 2 O 7 electrolyte at 220 °C and ambient pressure, the highest current efficiency of 7.1% and the highest NH 3 yield rate of 4.5 × 10 −10 mol (s −1 cm 2 ) were achieved at −0.4 V ( vs. open circuit voltage (OCV)) and −1.5 V, respectively. In addition, N 2 H 4 was successfully detected at −0.2 V ( vs. OCV), which indicated an associative mechanism, 4 which is one of the two main reaction mechanisms in NH 3 synthesis, namely, associative and dissociative mechanisms. In the associative mechanism the N N bond in a N 2 molecule adsorbed on the catalyst surface is cleaved after an H atom attaches to the N atom of the adsorbed N 2 molecule, whereas in the dissociative mechanism the N N bond is broken on the catalyst surface before an H atom attaches to the N 2 molecule.…”

“…In our previous study of the electrochemical NH 3 synthesis process at 220 °C, a ø 10 mm carbon paper was used on the cathode side to increase the current collection area. 4 However, in the in situ DRIFTS tests, the cathode catalysts must be exposed to the IR beam, hence a carbon ring with an inside diameter of 7 mm was used instead as shown in Fig. 3 .…”

“…In our previous work of the electrochemical NH 3 synthesis using Fe/BZY-RuO 2 , we have successfully detected N 2 H 4 as well as NH 3 , which indicated the triple bond of N 2 was broken simultaneously with the addition of H. Fe/BZY was prepared in the same way as in the previous work. 4 The as-prepared Fe/BZY powder was mixed with RuO 2 powder, and then the mixture was reduced in H 2 flow at 220 °C for 1 h. To fix the electrolysis cell, the current collection materials and the Pt lead wires, PTFE sheets (Gore Hyper-Sheet Gasket, W. L. Gore & Associate, Inc., Delaware, USA) formed into rings were used as the support. The experimental conditions in the dome are similar to those in a single-chamber reactor.…”