Progress of electrochemical Synthesis of Nitric Acid: Catalyst Design-Mechanistic insights-Protocol-Challenges

Abstract

Nitrogen-based fertilizers are necessary to increase the agricultural output since nitrogen is the most frequent rate-limiting product. The main ingredients in almost all nitrogen-based fertilizers are ammonia and nitric acid; demand for these substances is significantly driven by global population and food production. Over the next few decades, the size and value of the ammonia and nitric acid markets will continue to be largely influenced by global population, which will have a significant impact on energy utility. Ammonia is synthesized via the high energy demanding Haber-Bosch process, and in the Ostwald process, ammonia is catalytically oxidized to prepare industrial grade nitric acid. As industrial synthesis of nitric acid requires astronomical units of energy and emits greenhouse gases into the atmosphere at an alarming rate. Hence, there is an immediate need to find an eco–friendlier alternative route to produce nitric acid. In the approaching century, the most advantageous method that has the potential to significantly alter the human lifestyle is the electrochemical production of nitrate/nitric acid by nitrogen oxidation. In this review article, we have discussed designs of catalysts, mechanistic insights and strategy adapted for in the electrochemical nitrogen oxidation reaction (N2OR). Emphasis has been made on the various challenges that exist during N2OR and the possible solution to overcome the hurdles.

Progress of electrocatalytic urea synthesis: strategic design, reactor engineering, mechanistic details and techno-commercial study

“…The nitrate reduction reaction (NO 3 RR) to ammonia (NH 3 ) involves extensive variation in the oxidation state of nitrogen, Table 1 Energy requirements for reducing nitrogen through protoncoupled electron transfer reactions [60][61][62][63]…”

Carbon black supported manganese phthalocyanine: Efficient electrocatalyst for nitrogen reduction to ammonia

“…NH 3 yield rate and FE are still limited due to competition; in particular, the hydrogen evolution reaction (HER) in watery electrolytes and the lower solubility (20 mg/L) of N 2 in electrolytes are the biggest obstacles for ENRR. 47,48 Transition metal-based electrocatalysts can be a good choice for nitrogen reduction due to the synergistic effect that weakens the nitrogen triple bond due to reverse electron transfer through the metal vacant d-orbital to the nitrogen anti-bonding (π*) orbital. 49 Single atom coordination of some transition metals (iron, cobalt, nickel, copper, etc.)…”

“…There are still some significant challenges to overcome before electrochemical ENRR can be widely adopted as a scaled–up substitute for the Haber–Bosch method. NH 3 yield rate and FE are still limited due to competition; in particular, the hydrogen evolution reaction (HER) in watery electrolytes and the lower solubility (20 mg/L) of N 2 in electrolytes are the biggest obstacles for ENRR 47,48 . Transition metal–based electrocatalysts can be a good choice for nitrogen reduction due to the synergistic effect that weakens the nitrogen triple bond due to reverse electron transfer through the metal vacant d–orbital to the nitrogen anti–bonding (π*) orbital 49 .…”