Chlorinated pharmaceuticals like diclofenac (DCF) pose persistent environmental risks due to their bioaccumulation and toxicity, necessitating advanced remediation strategies. Herein, an integrated electrochemical system was developed, combining a self-nitrogen-doped carbon nitride (CN)-supported PdNi (CN@PdNi) cathode for electrocatalytic hydrodechlorination (ECH) with a CN anode for oxidative mineralization in a single, sequential process. The CN@PdNi cathode achieved 98.6% ECH efficiency, selectively cleaving C–Cl bonds to mitigate toxicity, which is attributed to its structural merits, including a well-dispersed, albeit partially clustered, nanoparticle distribution, metallic Pd/Ni phases, predominant Pd ⁰ /Ni ⁰ states, and enhanced porosity. Subsequent CN anodic oxidation enabled 96.8% total organic carbon (TOC) removal, ensuring near-complete mineralization. Mechanistic studies via Electron paramagnetic resonance (EPR), quenching, LSV, and Tafel slopes revealed atomic hydrogen (*H) generated at Pd ⁰ sites as the primary reactive species, augmented by electron transfer. The system exhibited robust performance across varied conditions and exceptional stability (< 1% efficiency loss over 11 consecutive cycles). Toxicity assessments showed 3–5 Log ₁₀ unit reductions (ECOSAR) and mung bean germination rates improving from 68.7 to 99.8%. This dual-functional detoxification-mineralization strategy overcomes the limitations of single-step processes and offers a scalable, sustainable solution for efficient remediation of halogenated pollutants.

The electrocatalytic reduction of nitrate (ERN) to ammonia offers a promising route to address energy shortages and environmental pollution, but its practical application is hindered by low selectivity due to complex eight-electron transfer pathways and high energy consumption (EC) from the kinetically sluggish oxygen evolution reaction (OER). This study proposes a dual strategy: (1) designing a multi-functional self-supported ANP electrode via vapor deposition to enhance ERN activity and (2) replacing the OER with thermodynamically favorable anodic reactions (urea oxidation reaction (UOR), sodium metabisulfite oxidation reaction (S(IV)OR), sulfite and urea oxidation reaction (S(IV)/UOR)) to reduce EC. The ANP cathode achieved a nitrate removal rate (R%) of 97.7%, ammonia selectivity (SE%) of 91.8%, and Faradaic efficiency (FE) of 97.3% at −1.2 V, with an ammonia yield of 0.0616 mmol h⁻¹ mg⁻¹ and an EC of 8.239 kWh/kg, while in situ-generated atomic hydrogen (*H) was identified as key to improving nitrate removal and selectivity. Replacing the OER with alternative anodic reactions significantly improved system efficiency: the UOR reduced EC by 17.5%, S(IV)OR saved 27.6% energy with 7.1% higher ammonia yield, and a hybrid S(IV)/UOR system achieved a 32.1% lower EC and a 12.6% greater ammonia yield than the OER. These differences stemmed from variations in cell voltage and ammonia production rates. This work provides a viable approach for selective nitrate-to-ammonia conversion and guides the design of energy-efficient electrocatalytic systems for sustainable nitrogen recovery.

Ozone (O₃) and fine particulate matter (PM_2.5) are critical atmospheric pollutants whose complex chemical coupling presents significant challenges for multi-pollutant control strategies. This study investigated the spatiotemporal variations and driving mechanisms of O₃ and PM_2.5 in Jiaxing, China, during different COVID-19 lockdown periods from November 2019 to January 2024. Using high-resolution monitoring data, random forest modeling, and HYSPLIT backward trajectory analysis, we quantified the relative contributions of anthropogenic emissions, meteorological conditions, and regional transport to the formation and variation of O₃ and PM_2.5 concentrations. The results revealed a distinct inverse relationship between O₃ and PM_2.5, with meteorologically normalized PM_2.5 decreasing significantly (−5.0 μg/m³ compared to the pre-lockdown baseline of 0.6 μg/m³), while O₃ increased substantially (15.2 μg/m³ compared to the baseline of 5.3 μg/m³). Partial dependency analysis revealed that PM_2.5-O₃ relationships evolved from linear to non-linear patterns across lockdown periods, while NO₂-O₃ interactions indicated shifts from VOC-limited to NO_x-limited regimes. Regional transport patterns exhibited significant temporal variations, with source regions shifting from predominantly northern areas pre-lockdown to more diverse directional contributions afterward. Notably, the partial lockdown period demonstrated the most balanced pollution control outcomes, maintaining reduced PM_2.5 levels while avoiding O₃ increases. These findings provide critical insights for developing targeted multi-pollutant control strategies in the Yangtze River Delta region and similar urban environments.