Global warming and wastes disposal are among the main environmental concern that we face today. Livestock (especially cattle) and diverse agro-industrial wastes can generate and, therefore, release large tones of carbon dioxide and methane into the atmosphere per year. After carbon dioxide, methane is regarded as the second most important greenhouse gas in terms of impact on the climate. There is a great interest in developing capable and feasible technologies that can convert these available greenhouse gases into value-added products, thus reducing their emission into the atmosphere. Carbon dioxide has often been more studied than methane. As a result, some materials such as copper, silver, tin, and bismuth have already exhibited good performance. However, methane recovery and conversion strategies have demanded a high quantity of energy and, hence present cost-prohibitive. Electrochemical techniques are particularly desirable to replace the limitations of traditional thermal catalysis as they are fossil-free and sustainable. Some of the electricity required to conduct methane electrocatalysis may be supplied by solar energy, a sustainable and inexpensive energy source. This hybrid photo/electron-driven combined with suitable catalysts can overcome such energetic barriers even at low temperatures (<100 °C) and enable better control of the selectivity, that is, turning methane into profitable organic molecules. Semiconductor structures are the most favorable for these types of reactions, although most of them have achieved low efficiency for partial or selective oxidation of methane into value-added products. On the other hand, complex heterostructures have demonstrated successful results for heterogeneous photoelectrocatalytic reactions since part of the structure acts as a cathode (typically a p-type semiconductor), while the other part acts as an anode (n-type semiconductor). A proper understanding of the different system parts is essential to boost efficiency. Nevertheless, it is still poorly explored in the literature. Factors such as photoelectrocatalyst role, reactions at interfaces (electrode/electrolyte), and reaction mechanism may provide essential information to control the reaction extension. This control may enable the production of hydroxyl radicals (*OH) that react in specific methane sites with a determined energy rate to produce particular chemicals (liquid fuel, for example). Along these lines, an electrochemical cell comprised of complex nanoparticulate photoelectrocatalysts composed of two aligned epitaxially attached phases is desired. In previous studies, the heterostructured nanoparticles TiO2:SnO2, WO3:TiO2, and g-C3N4/Nb2O5 were revealed to be efficient for the oxidation of different emerging pollutants in water and it possess sufficient potential to oxidize methane. From this perspective, this type of material can be a strong candidate to achieve an economical, more efficient, and environmentally attractive conversion of methane into value-added products. In this context, this project aims to unveil the role of each catalyst mentioned and its reaction mechanisms. The catalysts will be synthesized, and some predefined conditions, such as potentials, presence of oxidants agents, and electron acceptor use will be assessed. Advanced characterization techniques as XRD, N2 physisorption, SEM-FEG, and in situ TEM will be employed to support the studies of the catalysts. Techniques such as XPS and FTIR will be carried out to understand kinetic reactions of product formation. Lastly, NMR and CG will be used to identify the formed compounds. The outcome of the proposed research will be essential to understanding the methane oxidation facets under mild conditions and thus indicate the best photoelectrocatalyst to obtain gainful both liquid and gas products.
News published in Agência FAPESP Newsletter about the scholarship: