Preparation of Electrochemical Sensor Based on Morphology-Controlled Platinum Nanoparticles for Determination of Chemical Oxygen Demand

Platinum nanoparticles with different shapes, such as spheres, rhombs and flowerlike sheets, were in situ deposited on the surface of Pt disk electrode via reduction of 1 mM H2PtCl6 in 0.1 M H2SO4. By variation of reduction potential and time, the morphology and catalytic activity of Pt nanoparticles were readily tuned. Electrochemical tests revealed that the response of chemical oxygen demand (COD) on nano-Pt surface was shape-dependent. Compared with nanospheres and nanorhombs, the flowerlike Pt nanosheets which were deposited at −0.3 V for 2 min greatly increased the response current of COD, displaying strong signal enhancement for COD. The influences of pH value and detection potential were discussed. As a result, a novel electrochemical sensor using flowerlike Pt nanosheets as sensing film was constructed for COD, and the detection limit was 1.83 mg L−1. It was used for different lake water samples, and the results consisted with the values obtained by the national standard method.