Synergistic Integration of nickel sulfide clusters in hierarchical perylene-polyimide conductive frameworks for energy-efficient electrochemical urea oxidation reaction

The urea oxidation reaction (UOR) plays a crucial role in advancing electrochemical energy storage systems and in the remediation of urea-contaminated wastewater. However, progress in UOR technology has been hindered by the lack of efficient, cost-effective catalysts. Herein, a functional UOR electrocatalyst, NiS@PPI-TAPT, was developed through uniformly embedding nickel sulfide (NiS) clusters within a porous perylene-based polyimide framework (PPI-TAPT). The resulting catalyst exhibits hierarchical porosity and a spherical microstructure, which significantly enhance active site accessibility and surface area. Additionally, the conjugated structure of the polyimide framework enables rapid electron transfer, thereby improving UOR performance compared to its naphthalene-based analogue, NiS@PPI-TANT, which shows an uneven distribution of NiS. In an electrolyte solution of 1 M KOH containing 0.33 M urea, NiS@PPI-TAPT achieves a current density of 10 mA cm⁻² at a low potential of 1.39 V vs . RHE, surpassing conventional water oxidation systems (e.g., oxygen evolution reaction). Notably, at a current density of 100 mA cm −2 , the overpotential for UOR is 209 mV lower than that of the OER. Moreover, the catalyst demonstrates exceptional reaction kinetics (Tafel slope: 55 mV dec⁻¹) and minimal charge-transfer resistance, highlighting its energy-efficient in urea oxidation. This work presents a rational strategy for designing high-performance, low-cost UOR electrocatalysts through the integration of metal sulfides with conductive porous organic frameworks.