Enhanced Electrochemical Nitrate‐to‐Ammonia Performance of Cobalt Oxide by Protic Ionic Liquid Modification

Abstract

Electrochemical conversion of nitrate to ammonia is an appealing way for small-scale and decentralized ammonia synthesis and waste nitrate treatment. Currently, strategies to enhance the reaction performance through elaborate catalyst design have been well developed, but it is still of challenge to realize the promotion of reactivity and selectivity at the same time. Instead, a facile method of catalyst modification with ionic liquid to modulate the electrode surface microenvironment that mimic the role of the natural MoFe protein environment is found effective for the simultaneous improvement of NH 3 yield rate and Faradaic efficiency (FE) at a low NaNO 3 concentration of 500 ppm. Protic ionic liquid (PIL) N-butylimidazolium bis(trifluoromethylsulfonyl)imide ([Bim]NTf 2 ) modified Co 3 O 4À x is fabricated and affords the NH 3 yield rate and FE of 30.23 � 4.97 mg h À 1 mg cat.À 1 and 84.74 � 3.43 % at À 1.71 and À 1.41 V vs. Ag/AgCl, respectively, outperforming the pristine Co 3 O 4À x . Mechanistic and theoretical studies reveal that the PIL modification facilitates the adsorption and activation of NO 3 À as well as the NO 3 À -to-NH 3 conversion and inhibits hydrogen evolution reaction competition via enhancing the Lewis acidity of the Co center, shuttling protons, and constructing a hydrogen bonded and hydrophobic electrode surface microenvironment.

Schottky Junctions with Bi@Bi2MoO6 Core-Shell Photocatalysts toward High-Efficiency Solar N2-to-Ammonnia Conversion in Aqueous Phase

“…The photoactivities of core-shell Bi@Bi2MoO6 composites for N2-to-ammonia conversion have been investigated using deionized water without any scavenger. The produced NH3 is spectrophotometrically measured based on the indophenol blue method [49]. The amount of ammonia over Bi2MoO6 and core-shell Bi@Bi2MoO6 composites with different contents of metal Bi confirmed by the ICP measurement is shown in Figure 6a.…”

Ultrasmall Iron Nanoparticle-Decorated Carbon Black for High-Efficiency Nitrate-to-Ammonia Electrosynthesis and Zinc-Nitrate Batteries

“…Although nitrate electroreduction is promising as a decentralized route to ammonia synthesis, the high-efficiency conversion of nitrate to ammonia with high selectivity remains challenging because of the complex eight-electron and multiple proton transfer pathways accompanied by competitive hydrogen evolution reaction. , Moreover, various byproducts during the NO 3 – RR process make low selectivity for ammonia production. Efficient electrocatalysts are key for achieving high-efficiency NO 3 – -to-NH 3 conversion as well as various electrochemical reactions. − Substantial progress has been made for developing highly efficient electrocatalysts, including carbon-based catalysts, atomically dispersed metal–nitrogen-carbon catalysts, , and metal-based catalysts. − Among these catalysts, nonprecious metal-based catalysts have witnessed increasing interest due to their high electrocatalytic performance for cost-effective ammonia production with a high yield rate and Faradaic efficiency (FE). Especially, Fe-based nanomaterials [e.g., Fe single-atom catalysts and Fe nanoparticle (NP) catalysts] are promising as electrocatalysts for NO 3 – RR due to their abundance, inexpensiveness, and moderate adsorption energy of oxygen and nitrogen on Fe sites. − For instance, Wang and co-workers reported a Fe single-atom catalyst for nitrate electroreduction, which showed a yield rate of 4760 μg h –1 cm –2 and an ammonia FE of 86% .…”

Copper rhodium nanosheet alloy for electrochemical NO reduction reaction via selective intermediate adsorption

“…Electrochemical synthesis of ammonia has been a hot topic since the last decade due to the high demand of ammonia in various industries. 1,2 The traditional Haber-Bosch method requires harsh operating conditions (∼500 °C, >100 atm) to break the extremely stable NN bonds (941 kJ mol −1 ), which also results in considerable carbon emissions. Recently, an electrochemical nitric oxide reduction reaction (eNORR) has been considered as a clean route for ammonia production with mild operating conditions.…”