Electrochemical synthesis of nitric acid from air and ammonia through waste utilization

Abstract

Commercial nitric acid (HNO3) and ammonia (NH3) are mostly produced through the Ostwald process and the Haber-Bosch process, respectively. However, high energy demand and enormous greenhouse gas accompy these processes. The development of economical and green ways to synthesize HNO3 and NH3 is highly desirable for solving the global energy and environmental crisis. Here, we present two energy-efficient and environmentally friendly strategies to synthesize HNO3 and NH3 at distributed sources, including the electrocatalytic oxidation of N2 in air to HNO3 and the electrocatalytic reduction of residual ${\rm NO_{3}^{-}}$ contamination in water to NH3. The isotope-labeling studies combined with theoretical calculation reveal the reaction path of the two proposed strategies, confirming the origin of the electrochemical products. Importantly, the electrooxidation-generated ${\rm NO_{3}^{-}}$ ions may also serve as reactants for the electroreduction synthesis of NH3 in the future. Our work may open avenues for energy-efficient and green production of HNO3 and NH3 at distributed sources.

Tuning Surface Electronic Structure of Two‐Dimensional Cobalt‐Based Hydroxide Nanosheets for Highly Efficient Water Oxidation

“…The in situ transformation of the catalyst in the OER process has been widely reported. [36] Yanmei Shi et al reported that tannin-NiFe is converted into Ni x Fe 1-x O y H z in the OER process, as the final OER catalyst, and shows excellent OER catalytic performance. [37] This inference can be further confirmed by the characteristic peaks of O 1s XPS spectrum (CoÀ O and Co-OH).…”

Unveiling the Activity Origin of a Copper‐based Electrocatalyst for Selective Nitrate Reduction to Ammonia

“…In this regard, a strategy of electrocatalytic nitrate reduction into ammonia was developed . Notably, this technique could be easily incorporated into an existing technological process to produce value‐added ammonium/ammonia and clean water (Supporting Information, Figure S1).…”

“…[28] In this regard, a strategy of electrocatalytic nitrate reduction into ammonia was developed. [29] Notably, this technique could be easily incorporated into an existing technological process to produce value-added ammonium/ ammonia and clean water (Supporting Information, Figure S1). However, the selectivity and Faradaic efficiency of this process were relatively low because of the complicated eight-electron reduction course from nitrate to ammonia and the competitive hydrogen evolution reaction.…”

Electrochemical Oxidation of Nitrogen towards Direct Nitrate Production on Spinel Oxides

“…These steps involve processes requiring high temperature and high pressure, resulting in high‐energy consumption and large amounts of carbon dioxide emission. However, despite the great practical value to replace Ostwald process, direct nitrogen oxidation reaction (NOR) under mild conditions remains largely unexplored . Electrochemical techniques have been widely employed in the synthesis of value‐added products, owing to the feasibility of non‐thermal activation initiated by the applied potential .…”