Developing energy-efficient nitrate-to-ammonia flow cells with bifunctional NiFeW-oxide thin-film electrodes made by magnetron sputtering technique

• Published in: Applied catalysis. B, Environmental Environmental, 2024-10, Vol.354, p.124137, Article 124137
• Main Authors: Ha, Quoc-Nam, Hsiao, Wen-Chuan, Chan, Yu-Chan, Gemeda, Tadele Negash, Urgesa, Merga Hailemariam, Kuo, Dong-Hau
• Format: Article
• Language: English
• Subjects: Electrocatalytic nitrate reduction; Energy consumption; Energy efficiency; NiFeW-oxide; Oxygen vacancy
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2024.124137

Herein, we develop a sputtered NiFeW-oxide thin-film bifunctional electrocatalyst with the incorporated oxygen vacancies and multivalent cations of Ni2+/3+, Fe2+/3+, and W6+ to enhance the economic viability of electrocatalytic nitrate reduction for commercial applications. Our NFW-0.5 achieves a notable 54.6 mg/h.cm2 ammonia yield rate at a modest applied potential of −0.2 V vs. RHE, coupled with an outstanding Faradaic efficiency of 93.7%. Furthermore, our NFW-0.5(+)‖NFW-0.5(−) flow-cell electrolyzer with a larger electrode of 2×2 cm2 reveals an impressive ammonia productivity of 143.5 mg/h.cm2 at a cell voltage of 2.0 V, accompanied by a superior Faradaic efficiency of 96.1%, an energy efficiency of 26%, and a low energy consumption of 26.3 kWh/kg.NH3. An oxygen vacancy-based NO3-pinned mechanism is proposed to explain our excellent nitrate reduction. Our work introduces a new paradigm to design efficient and bifunctional electrocatalysts for potential industrial-scale ammonia production. [Display omitted] •Sputtered NiFeW-oxide films as bifunctional electrocatalysts for nitrate reduction.•Incorporating W into the NiFe structure enhances both NO3RR and OER performance.•NFW-0.5(+)||NFW-0.5(−) performed 143.5 mg/h.cm2 and Faradaic efficiency of 96.1 %.•NO3RR cell showed energy efficiency of 26 % and energy consumption of 26.3 kWh/kg.