The use of solar light for the production of electricity or liquid fuels of low environmental impact could drive the economy of the future.
Here, we must use the conditional tense. Today, hydrogen is produced mainly from hydrocarbons such as methane, so is not green and is certainly not renewable. The production of electricity using photovoltaic systems does not guarantee the continuity and power required. Yet all it takes is to absorb sunlight effectively and use this energy to produce electrical energy directly with high efficiency, or to separate water into hydrogen and oxygen.
Finding the right material to trigger the separation, however, is far from simple. This is explained by Alberto Vomiero, physicist, Professor of Industrial Engineering at Ca' Foscari, who arrived in Venice thanks to the law for the "return of brains", after a Marie Curie Fellowship in Canada and several years in Sweden, where he leads a research laboratory at the Luleå University of Technology (LTU).
“It is difficult to estimate when we will have enough hydrogen for a greener global economy,” he says, “or to have low-cost, low environmental impact photovoltaic systems that can compete with silicon solar panels. We are seeking advanced materials, possibly not rare and precious, that can render the numerous reactions that regulate these processes more efficient and therefore less costly. Many mechanisms are not yet clear. Unfortunately, the necessary characteristics often exclude one another. To be assembled in complex systems, for example, these materials must be good electrical conductors, absorb sunlight and have an uneven surface.” “Whoever finds the solution will win the Nobel Prize,” he says, smiling.
Vomiero, internationally renowned expert in the development of advanced nanomaterials for energy applications and Associate Editor of the prestigious journal Nano Energy (Elsevier), who works on nanomaterials for energy, recently became part of the Advisory Board of the journal Small (Wiley) and is the coordinator of the international PhD course in “Science and technology of bio- and nano-materials” at the Department of Molecular Sciences and Nanosystems, as well as fellow of numerous scientific societies (including the British Royal Society of Chemistry).
Vomiero’s team at the Luleå University of Technology, currently made up of 15 researchers, is testing compounds based on mixed oxides and disulphides of molybdenum, together with crystals of nanometric dimensions that can vary the colour of light absorbed with variation in size and shape.
The energy of the sun, depending on the case, can split water molecules directly or generate photovoltaic energy to activate the reaction. The challenge is played out in nanometric dimensions. Indeed, a thin film a few millionths of a millimetre can be applied to the material, with the dual purpose of protecting it, to make the operation of the material stable over time, and selecting the molecules with which it interacts, to boost the production of hydrogen.
This process, which is among the most promising, is called “confined catalysis” and represents a new frontier of research in the field.
“Isolation of the reaction using nanometric coatings is a sector undergoing strong growth and with many possible applications,” he explains. “From splitting water to produce hydrogen to the reduction of carbon dioxide to produce organic compounds with high added value. We are performing experiments to see whether the confinement of materials increases the efficiency and the duration of the catalyst.”
In the field of nanocomposites structured for the production of renewable energies through photovoltaic systems and production of hydrogen, Vomiero has described the state of the art in three articles published in the past three years in the leading scientific journal in this field, Advanced Energy Materials (Wiley), two of which were published as cover story due to their importance (articles here, here and here and the covers below).
Research in this filed is intrinsically multidisciplinary, requiring expertise in solid state physics, materials science, chemistry and electrochemistry. The main objective, which is the most complicated challenge, it understanding the correlation between the nanostructure of the materials produced and their functional characteristics.
To achieve the objective, advanced structural characterizations are essential, such as those soon to be possible in the centre of microscopy in the Department of Molecular Sciences and Nanosystems, which is acquiring new atomic-force microscopes, one transmission electron microscope and one latest-generation x-ray diffractometer.
“With the new instrumentation,” Vomiero concludes, “the department is capable of becoming an important player at national level in research on advanced materials for energy. This is one of the things that convinced me to return to Italy to continue the development of my research.”