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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. [ABSTRACT FROM AUTHOR]

Currently, great importance has been assigned to designing cutting-edge materials for oxygen and hydrogen generation from hybrid water electrolysis as an ideal fuel alternative in energy-conversion devices. This work reports on the electrochemical organic molecule oxidation in alkaline media, intending to promote water electrolysis at early onset potential with more current densities using Sn-Cu oxidized heterostructures. The electrocatalysts were easily and rapidly synthesized by the microwave-heated synthesis process in the presence of a small quantity of ethylene glycol. The X-ray diffraction and Field Emission Scanning Electron Microscopy analyses confirm the presence of CuO and SnO2 phases, which significantly improves the electrochemical activity of the composite toward the Oxygen Evolution Reaction (OER) in alkaline media in the presence of 1.0 mol L−1 ethanol, yielding 8.0 mA cm−2 at 1.6 V. The charge transfer resistance (Rct) was determined using electrochemical impedance spectroscopy, and the result shows that the Rct of SnO2/CuO drastically decreased. The findings in this work highlight that the designed oxidized heterostructures with non-noble metals are promising candidates for energy conversion devices and sensors. Furthermore, this work confirms the advantages of using an assisted microwave heating process to develop an advanced SnO2/CuO composite with the potential to be used in electro-oxidation processes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]