Platinum Metals Review - Volume 46, Issue 1, 2002

Much of the performance still to be gained in proton exchange membrane fuel cells (PEMFCs) in use today is available from improvements to the cathode, traditionally made from unsupported or carbon-supported platinum. The search for improved cathode electrocatalysts has resulted in the development of platinum alloys which if tailored to the desired stack operating conditions can double the activity for oxygen reduction. Recently, advances have been made in cathode design which have raised performance levels in PEMFCs. The new electrocatalysts and cathode designs have increased electrical efficiency and power densities to the PEMFC stack, needed for commercial use. Improvements have also been achieved at the anode, by developments in platinum-ruthenium anodes for carbon monoxide and cell reversal tolerance. In this first paper, new cathode materials and designs are discussed; a second paper to be published in the April issue will look at anode advances.

The destruction of hazardous organic waste produced as waste products in chemical processes has become an industry in itself, regulated by environmental agencies and government bodies. The environmentally harmful waste has been incinerated at high temperature with the aim of forming less harmful and less complex compounds, but this may lead to dioxin formation in the presence of chlorine-containing waste. It may also be treated electrochemically to result in carbon dioxide and water. One on-site electrochemical method, described here, which uses platinum-plated titanium electrodes, can treat most organic waste materials very effectively at low temperatures.

New technologies, incorporating the platinum group metals, are available to meet the exhaust emission regulations for cars, light-duty and heavy-duty vehicles and motorcycles being adopted by the European Union for implementation during the new century. These technologies include low light-off catalysts, more thermally-durable catalysts, improved substrate technology, hydrocarbon adsorbers, electrically heated catalysts, DeNOx catalysts and adsorbers, selective catalytic reduction and diesel particulate filters. This large range of technologies will allow exhaust emissions from all engines, both on- and non-road, to be lowered to unprecedented levels. This paper examines the state of emission control technologies currently available for all types of engine.