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

摘要

The electrochemical nitrite reduction reaction provides an alternativeapproach to offer sustainable ammonia source routes for repairing imbalancesin the global nitrogen cycle. In this work, electrocatalysis is combinedwith enzymatic catalysis to provide an efficient and clean process for recoverableammonia production. NO_2~? is reduced to NH_3 by electroenzymaticcascade reduction reaction on a bioconjugate, in which 1-butyl-3-methylimidazoliumbromide (IL_(BMB)) modified chloroperoxidase (CPO) is fixed onpolyethyleneimine (PEI) modified multi-walled carbon nanotubes (MWCNT)to from bioconjugate (CPO-IL_(BMB)/MWCNT-PEI). ~(15)N and ~(14)N isotope labelingreveal that the NH_3 species is derived from NO_2~? reduction. Density functionaltheory calculations identify that the FeII species in heme center of CPOserve as the key active site for NO_2~? reduction. The amino groups derivedfrom MWCNT-PEI not only serve as a bridge to covalently immobilize CPObut also enrich the NO_2~? ion at electrode/solution interface through electrostaticinteractions. The low energy barrier of NO_2~? reduction and low adsorptionfree energy of the intermediate result in high Faradaic efficiency (96.4%),NH_3 yield (112.7 mg h~(?1) mgCPO~(?1)), and high selectivity in pH 5.0 solution. Thehighly efficient electroenzymatic reaction ensurespromising applications inthe conversion of NO_2~? to NH3.