Mechanisms of Electroless Metal Plating : II . Formaldehyde Oxidation

A detailed investigation of the decomposition of formaldehyde was carried out to account for the fact that formaldehyde decomposition on Group VIII metals, e.g. , palladium, occurs without simultaneous hydrogen generation, while on Group I B metals, e.g. , copper, formaldehyde decomposition is accompanied by hydrogen evolution. It was found that, in principle, metals may be divided into three main classes: ( i ) metals with positive free energy of hydrogen adsorption, ( ii ) metals with free energy of hydrogen adsorption close to zero, and ( iii ) metals with negative free energy of hydrogen adsorption. In the case of class ( i ) metals, formaldehyde oxidation is accompanied by hydrogen evolution. For class ( ii ) metals, there is no simultaneous hydrogen evolution. Class ( iii ) metals show low catalytic activity for formaldehyde oxidation. Hence, formaldehyde cannot be used as a reducing agent for electroless plating of class ( iii ) metals.