Synthesis of ammonia directly from wet air using Sm_0.6Ba_0.4Fe_0.8Cu_0.2O_3−δ as the catalyst

Abstract

Ammonia was directly synthesised from wet air at 400 °C at atmospheric pressure. A new perovskite Sm(0.6)Ba(0.4)Fe(0.8)Cu(0.2)O(3-δ) was used as the electrocatalyst for electrochemical synthesis of ammonia. Ammonia formation rates of 9.19 × 10(-7) mol s(-1) m(-2) and 1.53 × 10(-6) mol s(-1) m(-2) were obtained at 400 °C when wet air and wet N2 were introduced into a simple single chamber reactor, respectively. The perovskite catalyst is low cost compared to the previously reported Ru/MgO and Pt/C catalysts. This experiment indicates that ammonia can be directly synthesised from wet air, a very promising simple technology for sustainable synthesis of ammonia in the future.

Role of Protons in Electrochemical Ammonia Synthesis Using Solid-State Electrolytes

“…Figure illustrates the log–log plot of the proton conductivities of the electrolytes and the ammonia synthesis rates using oxide, ,,− carbonate-based, − and polymer − proton-conducting electrolytes and cathode electrocatalysts (Pt, Ru, Pd, Ag, Fe, oxides, and nitrides) other than Ag–Pd. It must be noted that a linear correlation between the proton conductivity of the electrolyte and the ammonia formation rate cannot be found in Figure since the different chemical compositions of the cathode electrocatalysts exhibit different nitrogen affinity and coverage values.…”

“…Proton conductivity dependence of the electrochemical ammonia formation rate for oxide, ,,− carbonate-based, − polymer − proton conducting electrolytes and cathode electrocatalysts (Pt, Ru, Pd, Ag, Fe, oxides, and nitrides) other than Ag–Pd.…”

Role of carbonate phase in ceria-carbonate composite for low temperature solid oxide fuel cells: A review

“…The outstanding NH 3 synthesis rate suggests the significant proton conduction in the ceria–carbonate composite electrolyte. Although it is conflicted with the above claims of oxygen ionic domination property because of the applied different electrolyte compositions and operational conditions, it reflects the promising role of carbonate in composite by inducing the extrinsic proton conduction into the system, which will imply higher ionic conductivity, electrode reaction kinetics and fuel cell electrochemical performances, as well as multi‐functionality for advanced applications .…”

“…At their later work, they even observed that water was all yielded in the cathode of the ceria–carbonate (30 wt.%) composite electrolyte‐based fuel cell, which means that the ceria–carbonate is a pure proton conductor . In addition, Tao's group had conducted an extensive studies on the electrochemical synthesis of NH 3 using the ceria–carbonate ionic conductor and the newly developed electrode materials, and reached an NH 3 production rate of 1.83 × 10 −6 mol s −1 m −2 at 400 °C, which was three orders of magnitude higher than that of BaCe 0.85 Y 0.15 O 3 at similar operational conditions . The outstanding NH 3 synthesis rate suggests the significant proton conduction in the ceria–carbonate composite electrolyte.…”

New developments and challenges of solid oxide fuel cell (SOFC)-based technologies

“…With La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 − δ (LSCF) electrodes and BZCY electrolyte, the highest NH 3 synthesis rate was 8.5 × 10 −11 mol cm −2 s −1 at 550°C . With an oxygen ion conducting electrolyte, NH 3 is synthesized from N 2 and H 2 O mixture, enabling the possibility of direct NH 3 synthesis from wet N 2 or even from wet air . However, the rate of NH 3 electrochemical formation is usually at the order of 10 −11 – 10 −9 mol cm −2 s −1 at 400°C to 600°C, which is still too low for commercial applications.…”