Nanoporous Pt Catalyst Modified by Sn Electrodeposition for Electrochemical Oxidation of Formaldehyde

A nanoporous Pt particles‐modified Ti (nanoPt/Ti) electrode was prepared through a simple hydrothermal method using aqueous H₂PtCl₆ 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 SnCl₂ solution, to synthesize a Sn‐modified nanoporous Pt catalyst (Sn/nanoPt/Ti). Electroactivity of the nanoPt/Ti and Sn/nanoPt/Ti electrodes towards formaldehyde oxidation in a 0.5 mol·L^?1 H₂SO₄ 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 quasi‐steady 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^?1 with a sensitivity of 59.29 mA·cm^?2 (mol·L^?1)^?1. A detection limit of 0.506 mmol·L^?1 formaldehyde was found. The superior electroactivity of the Sn/nanoPt/Ti electrode for formaldehyde oxidation can be illustrated by a so‐called bifunctional mechanism which is involved in the oxidation of poisoning adsorbed CO species via the surface reaction with OH adsorbed on neighboring Sn sites.