Synergistic Electrochemical-Catalytic Hybrid System in Pt|Nafion|Pt–Cu Assembly Reactor for Efficient Nitrate Reduction

Abstract

To address the challenge regarding nitrate pollution from agriculture and industry, we developed a novel integrated system featuring a bimetallic membrane electrode assembly (Pt|Nafion|Pt–Cu) coupled with a suspended Pd–Cu/activated carbon (AC) catalyst for the nitrate reduction reaction (NRR) in low-conductivity media. This design leverages a synergistic mechanism, combining electrochemical reduction and catalytic hydrogenation for enhanced efficiency. The system demonstrated exceptional performance, achieving a high observed rate constant (k_obs = 43.2 × 10⁻³ min⁻¹) alongside superior product selectivity; notably low nitrite accumulation (15.8%) and high ammonia yield (63.3%) during batch electrolysis. This performance underscores the effectiveness of utilizing in situ electro-generated hydrogen, activated by the Pd–Cu/AC catalyst, in conjunction with Cu-surface modification for efficient and selective nitrate removal. Furthermore, the structural and chemical robustness of the electrode assembly was confirmed through comprehensive characterization via scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (PXRD) pre- and post-electrolysis. This work presents a promising, sustainable strategy for water remediation and the recovery of valuable nitrogen products.