The catalytic activity and electrochemical stability of Pd-CeO 2-NR /C (CeO 2-NR : cerium oxide nanorods) for the Oxygen Reduction Reaction (ORR) and the Ethanol Oxidation Reaction (EOR) is shown in alkaline media and compared to Pd/C. Evaluation of catalytic activity for the ORR in a Rotating Ring Disc Electrode (RRDE) setup , shows that Pd-CeO 2-NR /C promotes the reaction with a percentage of hydrogen peroxide production (%H 2 O 2) around 2-4 %, and an electron transfer number (n) close to 4. Tafel plots demonstrates higher mass and specific activities of Pd-CeO 2-NR /C than Pd/C. Moreover, from cyclic voltammetry tests, Pd-CeO 2-NR /C shows a higher mass catalytic activity (j m = 697 mA mg À 1 Pd) for the EOR at a more negative onset potential (E onset = 0.29 V/RHE) than Pd/C. After Accelerated Degradation Tests (ADT), Pd-CeO 2-NR /C retains ∼ 98 % of its Electrochemically Active Surface Area (ECSA), higher than ∼ 51 % of Pd/C. After ADT, the performance of Pd-CeO 2-NR /C remains similar for the ORR, while it is significantly higher for the EOR, compared to Pd/C. Thus, the addition of CeO 2-NR enhances the electrocatalytic behavior and stability of Pd towards the ORR and the EOR.

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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.