Nickel oxyhydroxide-functionalized n-silicon photoelectrode for the photocurrent determination of Hg(II) ions at zero working voltage

•A novel photoelectrochemical cell has been used for determination of Hg(II) ions.•We use a two-electrode system without applied voltage for Hg(II) ion detection.•This system has successfully averted from inconvenient reference electrode.•Mild media used for photocurrent measurement provides low noise of background.•The method is promising for simple, low-cost, portable, real-time, heavy metal ions detectors. Fast and accurate detection of aqueous mercury(II) ions is of significant importance as it raises serious risks for human health and the environment. Here, we report a photoelectrochemical determination of mercury(II) ions with nickel oxyhydroxide-functionalized n-silicon photoanodes at zero working voltage. Based on the catalysis effect of Hg(II) ions on the photocurrent of the catechol probe, a simple and sensitive photoelectrochemical sensor was constructed for Hg(II) ions detection in purified drinking waters (PW1, PW2 and PW3). The photocurrents show good response after the solution containing Hg(II) ions was added to the photoelectrochemically active catechol solution. Under the optimized conditions, the increase of photocurrent is proportional to the Hg(II) ions concentration, the linear dynamic range is observed from 10nM to 450nM with the detection limits of 5.4, 7.2 and 5.2nM in PW1, PW2 and PW3, respectively. Our work suggests that the two electrodes structures are promising for low-cost, portable, real-time, heavy metal ion detectors.