Biogenic synthesis of palladium nanoparticles: New production methods and applications

The palladium (Pd)-catalysed reaction has attracted much attention, making Pd the most valuable of the four major precious metals. Several different forms of Pd can be used as a catalyst; nanoparticles (NPs) have the advantage of a high surface area:volume ratio. Since the chemical production of Pd NPs is not environmentally friendly, biological synthesis interest has grown. However, the production mechanism remained unknown in several cases and was recently described for the electroactive bacterium Shewanella oneidensis MR-1. The application of these green synthesised NPs was established in different fields. This review discusses the production pathway and the novel biological-inspired methods to produce tailored biogenic palladium nanoparticles (bio-Pd NPs), with their broad application fields as biogenic nanocatalysts. Two significant applications - reductive bioremediation of persistent organic contaminants and energy-producing microbial fuel cells - are discussed in detail. The current challenges in optimising bio-Pd NPs production and the potential research directions for the complete utilisation of its novel catalytic properties are highlighted.