# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
## 4 Shape Control--A Way Forward
[PERSON] et al. [91,92] developed a programmed direct electrodeposition procedure to synthesize Pt, Pd tetrahexahedral (THH) nano crystals bounded by [730] high index facets. Pt nanoparticles previously electrodeposited on GC substrate were subjected to a square wave potential step. TEM images showed that the synthesized THH nanocrystals are bounded by 24 high index faces. Electrochemical studies showed that Pt, Pd THH nanocrystals displayed exceptionally high activities towards ethanol oxidation with high stability. The authors demonstrated the potentiality of the square wave technique to synthesize noble metal nanocrystals with high index faces, whose shape can be reconstructed by varying either the potential limits of a square wave or by changing the precursor concentration. [PERSON] et al. [93] demonstrated the feasibility of utilizing Pt nanoparticles efficiently by tailoring their shape on a tungsten carbide (WC) substrate via pulse electrodeposition and investigated the effect of particle shape on the electrochemical performance of the methanol oxidation reaction. The deposition potential had a considerable influence on particle shape, with the formation of cubic, dendritic particles at 0.14 V, 0.04 V vs. NHE (normal hydrogen electrode). Cu stripping voltammetry results showed that the preferential orientation for cubic particles is mostly [100] whereas, for dendrites, the orientation is along [111] direction. Electrochemical test data revealed that the Pt dendrites showed predominantly higher electrochemical performance towards methanol oxidation reaction than the cubic particles. Though there were noteworthy advances made in the shape-controlled synthesis of noble metals, most of the extensive investigations included the development of Pt, Pd nanostructures on ITO, Au, Si, and so on. Shape controlled noble metal (Pt, Pd) architectures were achieved via electrodeposition with or without stabilisers, surfactants, and templates. The development of template free noble metal crystals with various shapes, structures on carbon-based substrates would be beneficial for a variety of electro-catalytic applications besides fuel cells. Electrodeposition has the advantage of maintaining a high level of controllability since the electrode voltage or applied current is a useful parameter for influencing the structure of the metal synthesized. Deposition potential has a great influence on controlling the morphology of metal nanoparticles and is regarded critical for producing nanostructures by potentiostatic deposition. Controlling the surface structure of nanostructured metals using the deposition potential is a reliable approach to produce metal nanostructures with a preferred orientation, size, and shape. Because of the aforementioned advantages, electrochemical deposition methods have received a lot of attention in the synthesis of dendritic structures (which have a central stem from side branches). Furthermore, electrodeposition noble metal dendritic architectures will increase its electrochemical active surface area, making it more favourable and convenient for fuel cell applications. [PERSON] and his group [94; 95; 96; 97; 98; 99] addressed the challenge of obtaining palladium nanostructures on carbon based substrates without the need for a template/surfactant/structure directing agent. Dendritic Pd structures were synthesized on a carbon black (Vulcan) support coated on a graphite substrate using two different template free electrochemical techniques: cyclic voltammetry and constant voltage. The template/surfactant free methods developed by the group involved tuning of the morphology of palladium particles from spherical to dendritic structure, which is projected to eventually become the shape capture attribute of catalyst development for fuel cell applications. The methods developed demonstrated a new way of creating surface functional groups on the variety of carbon coated substrates (ranging from Vulcan mesoporous carbon, in-house wood apple carbon, to 2D graphene) through electrochemical activation.