Active hydrogen boosts electrochemical nitrate reduction to ammonia

Abstract

Electrochemical nitrate reduction to ammonia is a promising alternative strategy to the traditional Haber-Bosch process but suffers from a low Faradaic efficiency and limited ammonia yield due to the sluggish multi-electron/proton-involved steps. Herein, we report a typical hollow cobalt phosphide nanosphere electrocatalyst assembled on a self-supported carbon nanosheet array synthesized with a confinement strategy that exhibits an extremely high ammonia yield rate of 8.47 mmol h−1 cm−2 through nitrate reduction reaction, which is highly superior to previously reported values to our knowledge. In situ experiments and theoretical investigations reveal that the dynamic equilibrium between the generation of active hydrogen on cobalt phosphide and its timely consumption by nitrogen intermediates leads to a superior ammonia yield with a high Faradaic efficiency. This unique insight based on active hydrogen equilibrium provides new opportunities for large-scale ammonia production through electrochemical techniques and can be further used for carbon dioxide capture.

Efficient Electrocatalytic Nitrate Reduction to Ammonia Based on DNA-Templated Copper Nanoclusters

“…As the potential moved toward −0.2 V vs RHE, a band corresponding to another key intermediate appeared at ∼1294 cm –1 and was ascribed to NH 2 . Additionally, an upward band associated with NH 3 formation appeared at 3700 cm –1 , and the NO 2 – -related band at 1240 cm –1 disappeared . The in situ FTIR spectroscopy analysis suggests that, at −0.2 V vs RHE, NO 2 – was rapidly converted to NH 3 through intermediates, such as NH 2 OH and NH 2 .…”

“…62 Additionally, an upward band associated with NH 3 formation appeared at 3700 cm −1 , and the NO 2 − -related band at 1240 cm −1 disappeared. 63 The in situ FTIR spectroscopy analysis suggests that, at −0.2 V vs RHE, NO 2 − was rapidly converted to NH 3 through intermediates, such as NH 2 OH and NH 2 . Additionally, the upward band at ∼1636 cm −1 was attributed to water electrolysis, generating a proton during the NO 3 RR.…”

Highly Efficient Electrochemical Nitrate Reduction to Ammonia in Strong Acid Conditions with Fe2M‐Trinuclear‐Cluster Metal–Organic Frameworks

“…Similarly, high nitrate reduction efficiencies from most of the state‐of‐the‐art inorganic electrocatalysts were achieved in neutral or alkaline electrolytes, [11, 12] yet similar electrocatalytic nitrate reduction under strong acid conditions (such as pH=1) remain rare. Specifically, typical high‐efficiency electrocatalysts based on the noble metals (such as Ru, Pt, Pd, and Au) will suffer from the reduced Faradaic efficiencies (FEs) due to the obviously enhanced hydrogen evaluation reaction (HER) competition in acidic media, [13–16] whereas Fe/Co/Ni‐based catalytic systems (e.g., Fe−N−C, transition metal compounds) have a considerable risk of catalyst dissolution under strong acidic conditions [17–20] . Therefore, there is currently a lack of efficient NO 3 RR directly in acidic nitrate‐containing wastewater, to meet the requirements from a large number of industrial processes such as mining, metallurgy, metal processing, petrochemical and fiber engineering.…”

Highly Efficient Electroenzymatic Cascade Reduction Reaction For The Conversion of Nitrite to Ammonia

“…), such as nitrate and nitrite, are emitted more frequently with development of industry, which pollutes the environment. [15][16][17] NO 3 − can be easily reduced to NO 2 − . [18] The World Health Organization's International Agency announced that NO 2 − was a class 2A carcinogen in 2017.…”