Prof. Jenn Fang Su
Department of Chemical and Materials Engineering, Chang Gung UniversitySpeech Title: Selective Electrochemical Nitrate Reduction to Ammonium by a Homogeneous Multi-Element Catalyst
Abstract: Electrochemical conversion of nitrate (NO3⁻) to ammonium (NH4⁺) turns a hazardous aquatic pollutant into a valuable nutrient resource. Conventional operations involving single or binary metal catalysts suffer from inadequate selectivity and poor durability under acidic environments. Herein, we report a homogeneous multi-element catalyst, consisting of Cu, Ni, Pt, and Ru, synthesized via a rapid and effective Joule heating approach. The design utilizes the correlative roles of each component: Ru facilitates the initial adsorption of NO3⁻ species, while Cu serves as the primary site for N–O bond cleavage. In addition, Ni and Pt promote the hydrogenation required for NH4⁺ formation. Additionally, this quaternary composition increases electrochemically active surface area and accelerates electron transfer kinetics, leading to improved performance of NO3⁻-to-NH4⁺ reduction compared to ternary CuNiPt and CuNiRu counterparts. Specifically, an exceptional NO3⁻ conversion of 89.2%, an NH4⁺ selectivity of 89.6%, and an NH4⁺ formation rate of 1330 (g(h-1(cm-2 were achieved. Furthermore, a proof-of-concept zinc–nitrate battery incorporating homogeneous CuNiPtRu catalyst provides excellent rate reversibility and a peak power density of 21.9 mW·cm-2. This study outlines a promising platform for bypassing thermodynamic miscibility boundaries to engineer complex catalyst frameworks for environmental remediation and energy conversion.