Platinum and other metals are very scarce materials widely used in the energy and transportation sector among other sectors. Obtaining Platinum is becoming more difficult due to its scarcity on earth and because of the high amount of energy and water used for its extraction. In this regard, the recycling of platinum is necessary for sustainable technologies and for reaching a circular economy towards this expensive and rare metal. Conventional methods for platinum recycling make use of enormous amounts of energy for its recovery, which makes them not very attractive for industry implementation. Furthermore, these processes generate very toxic liquid streams and gas wastes that must be further treated, which do not meet the green environmental point of view of platinum recycling. Consequently, new advanced technologies are arising aiming to reach very high platinum recovery rates while being environmentally friendly and making a huge reduction of energy use compared with the conventional methods. In this review, conventional platinum recovery methods are summarized showing their limitations. Furthermore, new and promising approaches for platinum recovery are reviewed to shed light on about new and greener ways for a platinum circular economy.

In the near future, primary energy from fossil fuels should be gradually replaced with renewable and clean energy sources. To succeed in this goal, hydrogen has proven to be a very suitable energy carrier, because it can be easily produced by water electrolysis using renewable energy sources. After storage, it can be fed to a fuel cell, again producing electricity. There are many ways to improve the efficiency of this process, some of them based on the combination of the electrolytic process with other non-electrochemical processes. One of the most promising is the thermochemical hybrid sulphur cycle (also known as Westinghouse cycle). This cycle combines a thermochemical step (H₂SO₄ decomposition) with an electrochemical one, where the hydrogen is produced from the oxidation of SO₂ and H₂O (SO₂ depolarization electrolysis, carried out at a considerably lower cell voltage compared to conventional electrolysis). This review summarizes the different catalysts that have been tested for the oxidation of SO₂ in the anode of the electrolysis cell. Their advantages and disadvantages, the effect of platinum (Pt) loading, and new tendencies in their use are presented. This is expected to shed light on future development of new catalysts for this interesting process.

In this work, polybenzimidazole (PBI) membranes with different graphene oxide (GO) contents (0.5, 1.0, 2.0, and 3.0 wt %) as organic filler have been prepared. The X-ray diffraction confirms the incorporation of the filler into the polymeric membrane. The composite GO-based PBI membranes show better proton conductivity at high temperature (110–170 °C) than the pristine one. Moreover, the hydrophobicity of the PBI membranes is also improved, enhancing water management. The chemical stability demonstrates the benefit of the incorporation of GO in the PBI matrix. What is more, the composite PBI-based membranes show better phosphoric acid retention capability. For the first time, the results of the SO₂-depolarized electrolysis for hydrogen production at high temperature (130 °C) using phosphoric acid-doped polybenzimidazole (PBI) membranes with the different GO contents are shown. The benefit of the organic filler is demonstrated, as H₂SO₄ production is 1.5 times higher when the membrane with a content of 1 wt % of GO is used. Moreover, three times more hydrogen is produced with the membrane containing 2 wt % of GO compared with the non-modified membrane. The obtained results are very promising and provide open research for this kind of composite membranes for green hydrogen production by the Westinghouse cycle.