A nanoporous Pt particles-modified Ti （nanoPt/Ti） electrode was prepared through a simple hydrothennal method using aqueous H2PtC16 as a precursor and formaldehyde as a reduction agent. The nanoPt/Ti electrode was then modified with limited amounts of tin particles generated by cyclic potential scans in the range of -0.20 to 0.50 V in a 0.01 mol,L 1 SnCI2 solution, to synthesize a Sn-modified nanoporous Pt catalyst （SrdnanoPt/Ti）. Electroactivity of the nanoPt/Ti and Sn/nanoPt/Ti electrodes towards formaldehyde oxidation in a 0.5 moloL-I H2804 solution was evaluated by cyclic voltammetry and chronoamperometry. Electrooxidation of formaldehyde on the nanoPt/Ti electrode takes place at a potential of 0.45 V and then presents high anodic current densities due to the large real surface area of the nanoPt/Ti electrode. The formaldehyde oxidation rate is dramatically increased on the Sn/nanoPt/Ti electrode at the most negative potentials, where anodic formaldehyde oxidation is completely suppressed on the nanoPt/Ti electrode. Chronoamperogramms （CA） of the Sn/nanoPt/Ti electrode display stable and large quasisteady state current densities at more negative potential steps. Amperometric data obtained at a potential step of 100 mV show a linear dependence of the current density for formaldehyde oxidation upon formaldehyde concentration in the range of 0.003 to 0.1 mol.L-l with a sensitivity of 59.29 mA~cm-2 （mol,L-l）-1. A detection limit of 0.506 mmol.L-l formaldehyde was found. The superior electroactivity of the Sn/nanoPt/Ti electrode for formaldehyde oxidation can be illustrated by a socalled bifunctional mechanism which is involved in the oxidation of poisoning adsorbed CO species via the surface reaction with OH adsorbed on neighboring Sn sites.
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