Platinum black

Platinum black is a fine powder of platinum having good heterogeneous catalytic properties. The name of the platinum black is historic and was chosen because of its black color.

Platinum black is often used as a thin film of solid metal platinum, such as platinum electrodes, for use in the electrochemistry. The coating process is called Platinization of platinum for platinum electrodes with a layer of platinum black. The platinum- platinum has a catalytically active surface that is substantially greater than the geometric area of the electrode.

Platinum black is used as a catalyst in fuel cells. These platinum black is either sprayed or hot pressed onto the membrane and gas diffusion layer. A suspension of platinum black and carbon powder in ethanol-water solution is used to prevent the uniformity of the coating, the electrical conductivity and in the case of application to the membrane, drying out of the membrane during application.

Production of platinum black powder

Platinum black powder is produced from ammonium chloroplatinate by heating to 500 ° C in molten sodium nitrate for 30 minutes, quenching the melt in water, followed by cooking, washing and final reduction of the resulting brown powder, probably platinum dioxide with hydrogen to platinum black.

Platinization of platinum metal

The platinum surface is cleaned by immersion in aqua regia before Platinization. Platination is performed with the aqueous solution of chloroplatinic acid, lead acetate and a little at a current density of about 30 mA/cm2 for up to 10 minutes. In the process, chlorine evolved at the anode. After the platinizing, the electrode is rinsed and stored in distilled water. The electrode loses its catalytic properties by prolonged exposure to air.