Modulation of the electronic structure of a single-atom Ni catalyst for sensitive and simultaneous detection of dopamine and hydroquinone

Simultaneous electrochemical detection of dopamine (DA) and hydroquinone (HQ) is clinically significant but challenging because overlapping redox signals obscure detection on conventional sensing materials. Single-atom catalysts (SACs) offer promising adsorption and electron-transfer capabilities; however, limited synthetic control, poor cycling durability, and inevitable signal interference in complex multi-analyte matrices hamper their application. Herein, we report a nickel single-atom catalyst embedded in nitrogen-doped carbon (Ni SA/NC) with a unique electronic structure that enables simultaneous detection of DA and HQ. Benefiting from the unique Ni–N₄ moieties, the oxidation peaks for DA and HQ are well resolved, enabling simultaneous quantification. Notably, the Ni SA/NC achieves ultra-low detection limits (0.0018 μM for DA and 0.0017 μM for HQ), wide segmented linear response windows, and high anti-interference selectivity toward typical coexisting contaminants. Additionally, the Ni SA/NC exhibits outstanding measurement reproducibility, as evidenced by ultra-low relative standard deviations, alongside favorable storage stability. DFT calculations reveal that the Ni–N₄ configuration modulates the Ni d-band center to afford moderate *OH adsorption strength, thereby lowering the electro-oxidation barriers. Overall, this work establishes a rational design paradigm for SAC-based electrochemical sensing materials, offering potential for practical implementations in early disease diagnosis.