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Accurate determination of highly toxic organic pollutants in the water environment is urgent for the protection of environment and human health. Nevertheless, the development of sensitive nanomaterials for p-nitrophenol (PNP) and o-nitrophenol (ONP) electroanalysis remains a big challenge due to the electrochemical redox inertness of organics, which requires the nanomaterials to own considerable catalytic performance. In this work, FeSe 2 with high electronic conductivity and large active area was successfully prepared by hydrothermal synthesis and thermally induced selenization method. The results under the optimized conditions show that the FeSe 2 modified electrode exhibits high sensitivity (0.397 and 0.377 μA μM−1) and low detection limit (0.030 and 0.036 μM) for PNP and ONP, respectively. Besides, the catalytic rate constant, diffusion coefficient and adsorption capacity determined by chronoamperometry and adsorption experiments are 4745.06 M−1 s−1, 2.98 × 10−4 cm2 s−1 and 5.81 mg g−1, respectively, which indicate that the impressive electrochemical behavior of the prepared electrode should attribute to the combined effect of adsorption and catalysis. Moreover, the constructed high-efficiency sensor exhibits superior selectivity, stability, reproducibility, and also realizes the electrochemical detection of organic pollutants in subsidence area water samples. [Display omitted] • Combining hydrothermal method and thermally induced selenization, FeSe 2 was successfully prepared. • Hypersensitive detection of PNP and ONP was achieved by FeSe 2. • The impressive sensitivities for PNP and ONP are 0.397 and 0.377 μA μM−1, respectively. • The sensor exhibits high anti-interference and robust stability. • The synergistic effect of adsorption and catalysis improves the sensitivity of detection. [ABSTRACT FROM AUTHOR]

• Simple fabrication of small sized Co 3 O 4 /ZnO nanocomposite with oxygen vacancy. • Surface abundant oxygen vacancy enhanced the sensitivity of electroanalysis. • Co 3 O 4 /ZnO achieves high sensitivity (504.74 μA cm−2 μM-1) for Hg(II) detection. • The sensor exhibits high anti-interference and robust stability. Metal-oxide based nanocomposites have superior benefits to fabricate sensing interface for electroanalysis of heavy metal ions (HMIs) due to the introduction of various advantages (i.e. environmentally friendly, low-cost and high activity) into one material. Herein, Co 3 O 4 /ZnO nanocomposite with small size (sub-40 nm) and abundant oxygen vacancy was successfully prepared through one-step hydrothermal synthesis and subsequent annealing treatment, as well as the engineering of Co-Zn molar ratio. Moreover, the loose structure of Co 3 O 4 /ZnO nanocomposite can effectively improve the exposure of active sites on surface and enhance mass transfer. As a result, the as-obtained Co 3 O 4 /ZnO sensor has an impressive performance with sensitivity of 504.74 μA μM-1 cm-2 for electroanalysis of Hg(II) by square wave anodic stripping voltammetry (SWASV). Otherwise, diverse detection performances of the product with different Co:Zn molar ratio are investigated, proving the superiority for constructing Co 3 O 4 /ZnO sensor with molar ratio of 2Co/Zn. In addition, the electroanalytical behavior of the proposed sensors toward Hg(II) in subsidence area water was also realized with considerable result. By designing multifunctional nanocomposite with bimetal oxide nanomaterials, this work will provide a novel strategy to gain nanocomposite with controlling morphology and enriching oxygen vacancies, which are expected to be excellent candidate electrode materials for electroanalysis. [ABSTRACT FROM AUTHOR]