Verso un futuro sostenibile per l’energia. Produzione di H2 dall’acqua tramite energia solare

The availability of energy resources is a central element for the development of our society. Currently the production and use of energy (through energy carriers) are largely based on the exploitation of fossil fuels and the resulting impact on the environment, in terms of greenhouse gases emissions and polluting compounds, is causing increasing concerns. The transition to new and sustainable economy and society requires of accelerating the development and deployment of technologies that use “renewable” energy sources. In this context, the focus is primarily on solar energy, given that other sources, like traditional fuels, have a significant impact on the environment, as biomass on the water cycle, for example. In addition, although the photovoltaic cells are today widely diffuse, remain unsolved the problems related to: i) the discontinuity in the production of electrical energy which oblige in using energy storage systems and/or in integrating the photovoltaic systems with systems based on other energy sources, and ii) limits in the use of electricity for transport/energy storage purpose. To expand the use of solar energy it is now necessary solving the problem of the development of appropriate energy vectors (produced by solar energy) that allow an easy transport/storage of energy, and their inclusion in the current energy infrastructure at a low cost. In this perspective towards sustainability, the H2 production from water, by solar energy, along with an increased use of fuel cells (solved the problems of stability and the use of precious metals as catalysts in promoting cell processes) capable of converting, in turn, the chemical energy of hydrogen into electric energy, are key elements. This cycle allows overcoming the current problems of transport/energy storage, eliminating the production of greenhouse gases and pollutants such as NOx from fossil fuel combustion, but still only partially solves the problem of storage/transport, and it requires a significant investment in the energy infrastructure. For this rea-son, an alternative for the development could be to use the H2 produced by the sun for the conversion of CO2 to “solar” fuels (e.g. methanol) employing the fuels so produced in devices which allow, al the same time, CO2 recovery. In a longer-term perspective, this approach aims to develop artificial leaves that allow obtaining, from solar energy, water and CO2, a distributed production of energy carriers and chemicals. Therefore, solar energy use is a central element for a future sustainable energetic system, even though the challenges for its implementation are considerable.