A Novel Concept for Ammonia Synthesis

Ammonia — a carbon-neutral energy carrier — is a prospective transportation fuel that has an extensive application in plastics, fertilizers, and explosives. Traditional ammonia synthesis approaches depend mainly on the high-pressure and high-temperature Haber–Bosch method, leading to significant greenhouse gas emissions and energy consumption.

Developing the right solutions for attaining low-energy, high-efficiency, low-emission, and ecological ammonia production in benign environmental settings is crucial. The thermodynamically non-spontaneous ammonia synthesis reaction realized under ambient settings caused by electrical energy is enabled through electrochemical ammonia synthesis — a popular research topic.

Non-polar N₂ is insoluble in water — which restricts its activation and adsorption on the catalyst surface. At the reduction potential, the competitive hydrogen evolution reaction considerably decreases the production and Faradaic efficiency of N₂ reduction to ammonia. It is, therefore, important to identify novel electrocatalysts with high catalytic performance and examine the reaction mechanism of N₂ reduction to ammonia.

Recently, in the Journal of Energy Chemistry, a paper was published by Professor Luo Wenbin at Northeastern University and Li Feng at the Insititute of Metal Research. Mu Jianjia, a doctoral student at Northeastern University, is the first author of this study. The co-author of this study is Gao Xuanwen, an Associate Professor. Professor Luo Wenbin and Li Feng are the corresponding authors.

To create an integrated network for evading binder-induced side reactions, 3D nanowire arrays were grown on carbon cloth in this research, increasing the cycling lifespan.

In 0.1 M KOH electrolyte, the nitrogen reduction reaction (NRR) showed a high ammonia production rate (14.33 µg h⁻¹ mg_cat⁻¹) at -0.2 V and high Faradic efficiency (9.17%) at -0.1 V, outdoing the reported O_v-rich TiO₂-based electrocatalysts.

In the NRR in ambient settings, the synergistic effects of O_v and Ti³⁺ were theoretically and experimentally demonstrated, thus showcasing a new concept for highly capable electrocatalysts.

Journal Reference

Mu, J., et al. (2022) Boosting nitrogen electrocatalytic fixation by three-dimensional TiO_2−δN_δ nanowire arrays. Journal of Energy Chemistry. doi.org/10.1016/j.jechem.2022.08.007.