Photocatalytic H₂ Production and Carbon Dioxide Capture Using Metallurgical Slag and Slag-Derived Materials

Abstract

Consumption of fossil fuels increases year by year with negative impacts on the environment, particularly due to the emission of carbon dioxide (CO₂), a major anthropogenic greenhouse gas. Consequently, important scientific challenges for the upcoming years are the development of cleaner energy sources to satisfy the increasing energy demand, the reduction of the consumption of fossil fuels, and mitigation of the CO₂ emissions. Therefore, the production of renewable fuels with high energy content is researched, while efficient CO₂ capture is developed to reduce emissions from less-clean energy resources. For the former challenge, the production of hydrogen by heterogeneous photocatalysis is a potential solution. For the second problem, the use of solid sorbents for CO₂ capture as CaO and alkaline ceramics are promising proposals.

The development of catalysts and materials for CO₂ capture with high efficiency and stability as well as reasonable production costs is a great challenge. In the search for new efficient and inexpensive materials, metallurgical slags are quite attractive due to their physicochemical characteristics, abundance, and low cost. The high iron oxide content (>50% w/w) and the presence of crystalline phases such as fayalite (Fe₂SiO₄) and magnetite (Fe₃O₄) in the metallurgical copper slag indicate it may be active photocatalyst. On the other hand, the composition of the iron and steel slags makes these materials an excellent feedstock for the synthesis of CaO-based materials and other derived materials for CO₂ capture technologies.