# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 4 Shape Control--A Way Forward  
The unique electronic structure of nanosized metal particles, as well as their exceptionally large surface areas, have generated interest in the use of nanostructured catalysts. Because electrochemical reactions are surface sensitive, this property is critical for a catalyst's effective functioning [81]. The electrodeposition of noble metals such as Pt, Pd, and also deposit properties, which differ widely depending on the substrate, are well recognised. However, Pt deposition from aqueous solutions typically results in large catalyst particles ranging in size from 50 to 90 nm. To produce nanoparticles via electrodeposition, two fundamental modes of particle formation must be controlled: nucleation and growth. Nucleation is the intensity with which a stochastic arrangement of inbound atoms spontaneously arranges itself into a crystal, whilst the rate at which these nucleated zones spread outwards is referred to as growth. To form nanoparticles, growth must be controlled while nucleation is encouraged. [PERSON] et al. [82] worked on controlling the shape of Pt particles at desirable locations on Nafion-bonded carbon black substrates, through the introduction of shape control additives: poly ethylene glycol (PEG-10000), lead (II) acetate during pulse electrodeposition. Comparison of the morphological results evidenced the role of additives in obtaining shapes such as clump-like crystal aggregations, elongated leaf-like structures with PEG-10000, lead (II) acetate in contrast to spherical clusters obtained without them. The study demonstrated an alternative to the conventional method of preparation and a novel strategy to enhance the utilization of the Pt catalyst and its electrochemical active surface area through the introduction of shape control additives. [PERSON] et al. [83] aimed at improving the ORR performance of the cathode by minimizing the Pt loading in the electrode. They introduced a new pulsed electrodeposition method that combines the coating of Pt seeds on a Nafion-bonded carbon substrate, with the particle size and shape regulated by the addition of poly ethylene glycol (PEG) to the deposition solution. Electrodeposited Pt cathode catalyst, prepared by the coating of Pt seeds and PEG addition, was shown to perform better than the electrode prepared using commercial Pt/C catalyst. The authors discussed the possible reasons highlighting the beneficial effects of Pt seeds and PEG on the increased activity of prepared Pt cathode catalysts. They concluded that introducing PEG into the deposition solution would decrease the Pt/C particle size with controllable crystallite morphology and the adoption of the methodology would be very useful in the design and fabrication of fuel cell electrodes. Various Pt-based and Pd-based nano-architectures such as nanorods, nanowires, nanocubes, nanoplates, three-dimensional flower-shaped nanoparticles (nanoflowers), etc. have recently emerged as convincing nanomaterials for electrocatalysis due to their porous nature, large surface area, and more active centres. Few studies [84; 85; 86] presented a facile electrochemical approach to synthesize Pt nanflowers, Pd nanoplates arrays (NPAs) onto the glassy carbon, gold substrate through surfactant assisted cyclic potential scan, tested towards methanol oxidation. According to the studies, the electrode coated with NPAs exhibited a large active surface area and good catalytic activity and stability. To further explore the process, the same group synthesised Pd nanomaterials with varied morphologies on gold substrates using specially adapted surfactant-assisted cyclic potential scanning technique using various surfactants. The researchers concluded that this method provides an effective technique to deposit highly catalytic Pd nanoparticles, additional nanostructured noble metals such as Pt, Rh, and Au, and that it can be broadened to the formation of their binary alloys with high catalytic activity directly on the substrate.