Ni(OH)2/NiOOH nanonetwork-modified non-enzymatic integrated electrochemical sensor for urea detection in swimming pool water

An integrated three-electrode non-enzymatic urea sensor is developed. • The sensor exhibits a wide linear range (1–200 mg/L) and a fast response (10.8 s). • Detection potential dynamically regulates the contributions of the two urea oxidation pathways. Rapid and accurate monitoring of urea concentration in swimming pool water is critical for protecting swimmers' health and optimizing water quality management. However, traditional techniques are either expensive or operationally complex, whereas enzyme-based sensors suffer from enzyme deactivation, limiting their applicability for online monitoring. In this paper, a nickel hydroxide/nickel oxyhydroxide (Ni(OH) 2 /NiOOH) nanonetwork electrochemical sensor for non-enzymatic urea detection is proposed, which is mass-produced on a platinum electrode using microelectromechanical systems (MEMS). The electrode was activated and optimized via cyclic voltammetry by varying the scan rate. The sensor demonstrates a high sensitivity of 1.43 μA/(mg·L −1 ·cm 2 ), a wide detection range of 1–200 mg/L, a fast response time (<12 s), good repeatability with a relative standard deviation (RSD) of 1.24%, and an excellent linearity ( R 2  = 0.9988). In addition, the proposed sensor exhibits excellent anti-interference performance toward coexisting species such as creatinine, uric acid, residual chlorine, and lactic acid. Practical applications in swimming pool water samples yielded recovery rates of 92.5–100.4%, validating the sensor's robustness. Two distinct oxidation mechanisms for urea on the electrode were observed by electrochemical impedance spectroscopy (EIS). The direct pathway was further found to be potential-tunable, with its charge-transfer resistance decreasing by 35.6% upon raising the working potential from 0.45 V to 0.50 V. This work offers a promising route toward non-enzymatic urea sensors for swimming pool water monitoring. Download: Download high-res image (140KB) Download: Download full-size image