Nanoprecipitated CoPi enhanced photoelectrochemical water oxidation toward sensitive and selective Co²⁺ detection

The detection of heavy metal ions Co²⁺ is of great significance to the environment and human health. Herein, a simple, highly selective and sensitive photoelectrochemical detection strategy for Co²⁺ was developed based on the enhanced activity by nanoprecipitated CoPi on the Au nanoparticle decorated BiVO₄ electrode. The new photoelectrochemical sensor has a low detection limit of 0.03 μΜ and wide detection range of 0.1-10, and 10-6000 μΜ, with a high selectivity over other metal ions. The Co²⁺ concentration in tap water and commercial drinking water has also been successfully determined with the proposed method. Scanning electrochemical microscopy technique was employed to characterize the photocatalytic performance and heterogenous electron transfer rate of electrodes in situ, further revealing the photoelectrochemical sensing mechanism. Besides determining Co²⁺ concentration, this approach of enhanced catalytic activity by nanoprecipitation can be further extended to develop a variety of electrochemical, photoelectrochemical and optical sensing platforms for many other hazardous ions and biological molecules.