# Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications
Under such circumstances, electrochemical deposition is advocated as a cost-effective alternative synthesis method for obtaining metal particles of different crystalline nature (crystalline/amorphous) with various shapes, sizes without any post-processing requirement. This methodology offers certain key benefits such as mild operating conditions, high purity, relatively low cost, eliminating repetitive filtering and washing process [8,9]. Non-electrodeposition methods for synthesis of shape-controlled catalysts were limited as they rely on template techniques involving organic surfactants, polymeric substances with stabilisation effects at elevated temperatures, and the utilisation of structure-directing agents to control the porosity. The addition of these additives makes the current wet chemical processes difficult in obtaining pure products. While the quest for low-cost electrodes for fuel cells has been a focus of attention, extensive efforts have been made to investigate carbon decorated with electrodeposited noble metals as electrodes [10]. The advantage with electrodeposition methods is the possibility of synthesizing metal particles with different shapes, structures preferred orientation through tailoring the applied current, potential, electrolyte conditions. Despite the fact that Pt is the most advanced catalyst for low temperature DLFCs, its applicability is hampered by two main technological gaps: cost and long-term stability. Although practical ways to reduce cost and increase performance have been devised, the true breakthrough is yet to be realised. Currently, two approaches are being pursued to lower catalyst costs: investigating cost-effective non-Pt catalysts and reducing Pt loading. An ambitious strategy for cost reduction in fuel cells is to entirely replace Pt with less expensive materials while maintaining the catalytic activity [11]. Palladium (Pd) has received considerable attention in fuel cell research as an alternative to Pt because of its relative abundance and low cost. Pd is used in fuel cells, synthesis of organic compounds, hydrogen storage, automobile and sensing, and other industrial applications [12,13]. Pd plays a good role in various electrochemical reactions involving electro-oxidation of different fuels and oxygen reduction. Anodic oxidation of organic molecules such as ethanol and formic acid are important reactions, and Pd catalysts have proven to be much more active than Ptin direct formic acid fuel cells [14]. Prior research works on single crystal Pd electrodes demonstrated that the oxidation reaction of formic acid is structure sensitive, suggesting that the facets represented on the surface of a catalyst can have a major impact. Because of their superior methanol tolerance in PEM based direct methanol fuel cells (DMFCs) and increased activity, Pd-based nanoparticles are regarded as ideal alternative catalysts for oxygen reduction reactions (ORR). In an analytic data study conducted by [PERSON] et al., it was shown that there are 4674 articles that were reported focusing on the development of Pt, Pd catalysts for fuel cell applications in the past 3 decades covering the period from 1990-2019 [15], signifying the field of interest. Table 1 lists the most commonly studied DLFCs and their associated electrochemical reactions. The objective of this review is to present an overview of the progress made in the development of noble metal electrocatalysts prepared by electrodeposition for low temperature DLFCs. While several comprehensive review articles and books about the polymer electrolyte membrane fuel cells (PEMFC) electrocatalysts have been published over the past decade, most of them discussed the overall catalyst developments [5; 13; 17; 18; 19; 20; 21; 22; 23]. Detailed reviews consolidating the summary of the progress in the synthesis of Pt and Pd catalysts by electrodeposition are still scarce.