Gold: A relatively new catalyst

Work performed with gold catalysts before about 1980 is briefly reviewed, and early indications of the importance of using very small particles to obtain good activity are noted. The apparent contrast between silver and gold in catalysing carbon monoxide oxidation was anticipated by studies in matrix isolation chemistry. The unexpected and in some ways unique properties of gold are attributable to the operation of a relativistic effect which stabilises the 6s(2) electron pair. Essential requirements for high oxidation activity include: small particle size, use of 'reactive' support, and a preparative method that achieves the desired size of particle in intimate contact with the support. Surface atoms on such small particles behave more like individual atoms, and this together with awareness of the relativistic factor may help to explain why gold can be such an effective catalyst.