Semiconductor photocatalysis has many, varied applications with frequent research in environmental areas such as pollution abatement, heavy metal recovery, water and air purification and the destruction of microorganisms as well as hydrogen production from water, corrosion inhibition and self-cleaning surfaces. However, another field with considerable scope lies in the use of photocatalysis for metal deposition.
Photocatalytic metallisation of semiconductor surfaces is an established technology that has been employed predominantly to improve and enhance the photocatalytic properties of the semiconductor, a process known as doping. This review examines the use of semiconductor photocatalysis in driving conventional metal deposition techniques, in photocatalytic sensitisation of substrates prior to a further electroless deposition step and its potential utility in the initiation of electroless metal deposition for the formation of complete metal layers. The latter will focus particularly on the recently developed Photocatalytically Initiated Electroless Deposition (PIED) process, a one-step metal deposition process which utilises photocatalysis to directly metallise insulating substrate surfaces. The process is spatially selective and offers several advantages over traditional, non-photocatalytic techniques such as enhanced controllability and purity of the deposit as well as being operationally cheaper and environmentally cleaner with reduced material requirements and fewer preparation steps.
PIED has been successfully utilised to produce layers of various metals including Ag and Pd on mesoporous TiO2 (m-TiO2) coated quartz glass slides and polymer substrates. Such metallised insulating materials have potentially wide applications in membrane and separation technology, electrode / solid electrolyte composites for energy storage and fuel cells.