In situ growth of nanoflake and nanoflower-like Ni hydrated hydroxide on the surface of Ni foam as a free-standing electrode for high-performance phosphate detection

Environmental pollution has always been a global concern, e.g. water eutrophication caused by the high concentrations of phosphorous. It is especially important to detect harmful substances conveniently, quickly and accurately. This study reports a free-standing electrode composed of Ni foam (NF) and in situ grown nanoflakes and nanoflower-like Ni hydrated hydroxide (NHH) on the NF surface (NHH/NF) by a one-step hydrothermal method for phosphate detection. The NHH/NF electrode was directly applied as a binder-free and conductive agent-free working electrode in a three electrode system and showed a wide linear detection range of 10–50,000 μM, high sensitivities of 210 and 87 μA mM⁻¹ cm^-2 for the phosphate concentration ranges of 10–14,000 and 14,000–50,000 μM, respectively, and a fast response time of 6 s for phosphate detection in a NaOH solution (pH≈11). The nanostructure of the NHH layer not only provided a large surface area and rapid electron transfer but also protected the NF substrate from being degraded by the electrolyte and interfering species, thereby achieving good stability and selectivity. In addition, for artificial and real wastewater detection, the good recover ability presented here improves the prospects of developing a cost-effective, simple, and accurate sensor for phosphate detection.