Mechanisms of electroless metal plating: II. Decomposition of formaldehyde

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., Pd, occurs without simultaneous hydrogen generation, while on Group IB metals, e.g., Cu, formaldehyde decomposition is accompanied by hydrogen evolution. It was found that in principle metals may be divided into three main classes: (a) metals with positive free energy of hydrogen adsorption, (b) metals with free energy of hydrogen adsorption close to zero, and (c) metals with negative free energy of hydrogen adsorption. In the case of class (a) metals formaldehyde oxidation is accompanied by hydrogen evolution; for class (b) metals there is no simultaneous hydrogen evolution; and class (c) metals show low catalytic activity for formaldehyde oxidation. Hence, formaldehyde cannot be used as a reducing agent for electroless plating of class (c) metals.