The growing demands for ammonia in agriculture and transportation fuel stimulate researchers to develop sustainable electrochemical methods to synthesize ammonia ambiently, to get past the energy-intensive Haber-Bosch process. However, the conventionally used aqueous electrolytes limit N 2 solubility, leading to insufficient reactant molecules in the vicinity of the catalyst during electrochemical nitrogen reduction reaction (NRR). This hampers the yield and production rate of ammonia, irrespective of how efficient the catalyst is. Herein, we introduce an aqueous electrolyte (NaBF 4 ), which not only acts as an N 2 -carrier in the medium but also works as a full-fledged “co-catalyst” along with our active material MnN 4 to deliver a high yield of NH 3 (328.59 μg h −1 mg cat −1 ) at 0.0 V versus reversible hydrogen electrode. BF 3 -induced charge polarization shifts the metal d-band center of the MnN 4 unit close to the Fermi level, inviting N 2 adsorption facilely. The Lewis acidity of the free BF 3 molecules further propagates their importance in polarizing the N≡N bond of the adsorbed N 2 and its first protonation. This push-pull kind of electronic interaction has been confirmed from the change in d-band center values of the MnN 4 site as well as charge density distribution over our active model units, which turned out to be effective enough to lower the energy barrier of the potential determining steps of NRR. Consequently, a high production rate of NH 3 (2.45 × 10 −9 mol s −1 cm −2 ) was achieved, approaching the industrial scale where the source of NH 3 was thoroughly studied and confirmed to be chiefly from the electrochemical reduction of the purged N 2 gas.

Ammonia has been recognized as the future fuel because of its immense advantages over liquid hydrogen. The research trend nowadays is mostly inclined toward the electrochemical ammonia synthesis since it offers a sustainable method of green ammonia production. The indophenol blue method is one of the largely used colorimetric techniques to detect ammonia spectroscopically but lacks a proper experimental protocol. The unresolved speculations related to this method concerning stability of dye, sequence of mixing of reagents, importance of pH in the dye formation, or sensitivity of the method to interferants need vigorous experimental verification and a legitimate protocol has to be set up for a reliable and reproducible data. This work thus aims to unveil the artefacts of this method and explore the mechanisms involved such that it becomes easy for a newcomer as well as existing researchers in the field to understand the requirement of rigorous optimizations in this technique.