Chloroperoxidase Immobilized on Pd₂Ag Nanoparticles for the Electrocatalytic Reduction of Nitrate to Ammonia

Ammonia (NH 3 ) production by the Haber-Bosch method is one of the foremost commercial technologies; however, it suffers serious problems, such as high energy consumption and emission of greenhouse gas. Electrocatalytic nitrate reduction to NH 3 (NO 3 RR) provides a more prospective pathway for NH 3 production in terms of environmental problems and energy conversion. In this work, a nanobiohybrid composed by ionic liquid-modified chloroperoxidase (CPO-IL EMB ) immobilized on bimetallic Pd 2 Ag nanodendrites (Pd 2 Ag-BNs) was proposed for NO 3 RR through a novel electroenzyme cascade catalytic reaction. The electrocatalytic reduction of nitrate (NO 3 – ) to nitrite (NO 2 – ) was achieved using Pd 2 Ag-BNs, followed by CPO-IL EMB ’s enzymatic transformation of NO 2 – to NH 3 . Herein, Pd 2 Ag-BNs not only promoted the electrocatalytic conversion of NO 3 – to NO 2 – but also immobilized CPO-IL EMB via electrostatic interaction. In an electroenzymatic cascade catalysis system, Pd 2 Ag-BNs boosted the reduction efficiency of NO 3 – to NO 2 –, and CPO-IL EMB subsequently transformed NO 2 – to NH 3 . This electroenzymatic cascade catalysis system could achieve a high Faraday efficiency of 97.1% and a high NH 4 + yield of 109.91 mg·h –1 ·mg cat –1 for NO 3 RR in a neutral solution.\