The oxygen reduction reaction (ORR) is the oldest studied and most challenging of the electrochemical reactions. Due to its sluggish kinetics, ORR became the major contemporary technological hurdle for electrochemists, as it hampers the commercialization of fuel cell (FC) technologies. Downsizing the metal particles to nanoscale introduces unexpected fundamental modifications compared to the corresponding bulk state. To address these fundamental issues, various synthetic routes have been developed in order to provide more versatile carbon-supported low platinum catalysts. Consequently, the approach of using nanocatalysts may overcome the drawbacks encountered in massive materials for energy conversion. This review paper aims at summarizing the recent important advances in carbon-supported metal nanoparticles preparation from colloidal methods (microemulsion, polyol, impregnation, Bromide Anion Exchange…) as cathode material in low temperature FCs. Special attention is devoted to the correlation of the structure of the nanoparticles and their catalytic properties. The influence of the synthesis method on the electrochemical properties of the resulting catalysts is also discussed. Emphasis on analyzing data from theoretical models to address the intrinsic and specific electrocatalytic properties, depending on the synthetic method, is incorporated throughout. The synthesis process-nanomaterials structure-catalytic activity relationships highlighted herein, provide ample new rational, convenient and straightforward strategies and guidelines toward more effective nanomaterials design for energy conversion.

Water splitting technology is an innovative strategy to face the dependency on fossil fuels and, at the same time, address environmental pollution issues. Electrocatalysts seem to be the better option to improve water separation efficiency and satisfy the commercial-scale demand for hydrogen. Therefore, the design and fabrication of heterostructures with a high affinity for achieving water splitting have been proposed. In this review, the application of several electrocatalysts for hydrogen and oxygen evolution reactions is presented and discussed in detail. A review of the recent advances in water separation using noble metals such as Pt-, Ir-, and Ru-based electrodes is presented, followed by a highlighting of the current trends in noble-metal-free electrocatalysts and novel preparation methods. Furthermore, it contemplates some results of a hybrid organic molecule–water electrolysis and photoelectrochemical water splitting. This review intends to give insight into the main trends in water splitting and the barriers that need to be overcome to further boost the efficiency of the main hydrogen and oxygen generation systems that ultimately result in large-scale applications. Finally, future challenges and perspectives are addressed, considering all the novelties and the proposed pathways for water splitting.

Palladium nanoparticles supported on a pretreated carbon substrate (Pd/C) were synthesized from a surfactant‐free microwave‐heated ethylene glycol without any external reducing agent and characterized by high‐resolution electron transmission microscopy, thermogravimetric analysis, and X‐ray diffraction analysis. Cyclic voltammetry was effectively employed to scrutinize the electrochemical processes such as Pd hydrogen interactions including hydrogen adsorption, absorption, desorption, and hydrogen evolution as well as Pd–oxygen interactions like the oxide formation and the subsequent reduction of the oxide layer. The electrochemical oxidation of palladium was clearly indicated at the potential ranging from 0.78 to 1.20 V versus reversible hydrogen electrode (RHE) in the anodic scan direction whereas the corresponding reduction peak was observed with a broad peak centered at 0.79 V versus RHE in the reverse scan. Therefore, an accurate evaluation of the EASA measurements on ultrathin film palladium (Pd/C) electrodes in acidic (0.5 mol L ⁻¹ H ₂ SO ₄ , pH ∼ 1) media was successfully conducted. Moreover, the steady‐state cyclic voltammetry (CV) measurements have been conducted at the lowest scan rate of 1 mV s ⁻¹ , enabling obtaining of hydrogen adsorption, absorption, and desorption reaction features without concurrent. Besides, Pd/C electrocatalyst exhibited 129 mV overpotential yielding a cathodic current density of 10 mA cm ⁻² toward hydrogen evolution reaction. This study outlines the description of practical experimental conditions essential for accurately determining the EASA that facilitates a comprehensive evaluation of their electrochemical performance.