Energy Changes
Water does not spontaneously separate into hydrogen and oxygen under normal conditions. Energy must be supplied. Solar thermochemical systems attempt to supply this energy through concentrated sunlight.
Unit 02 Thermodynamic Chemistry
Producing HydrogenUsing Solar Energy
Article
Perry, J., Molina, L., de la Calle, A., et al. (2025). Discovery of materials for solar thermochemical hydrogen combining machine learning, computational chemistry, experiments and system simulations. npj Computational Materials, 11, 247.
Read The Original ArticleThe study combined first-principles calculations, computational chemistry, machine learning, experiments, and system modelling to investigate redox perovskites for solar thermochemical hydrogen production.
Abstract
Hydrogen is an important potential energy carrier because it can be used as a fuel without directly producing carbon dioxide during its use. However, hydrogen must first be produced, and splitting water into hydrogen and oxygen requires energy. This scientific study investigated materials that could improve solar thermochemical hydrogen production. In this process, concentrated sunlight provides thermal energy that drives reversible redox reactions involving metal oxides. Researchers combined machine learning, computational chemistry, experiments, and system simulations to identify materials with favourable thermodynamic properties.
One important property examined by the researchers was the energy associated with creating oxygen vacancies in the metal oxide. The researchers identified a perovskite material that could undergo reduction under less extreme temperature conditions than a commonly studied cerium-oxide benchmark under the reported conditions. The study demonstrates that understanding thermodynamic properties at the molecular level can help scientists design materials that use solar energy more efficiently. It also demonstrates how computer modelling and experimental chemistry can work together when developing future energy technologies.
Connection to Our Curriculum
Enthalpy
A major idea in the paper is the energy required to create an oxygen vacancy in the metal oxide. This relates directly to enthalpy change. Different materials require different amounts of energy for chemical changes to occur.
ΔH
Endothermic Processes
The high-temperature reduction step requires thermal energy. Because energy is entering the chemical system, the reduction process involves an important endothermic component.
Metal oxide + heat ⇌ reduced metal oxide + O₂
Hydrogen Production
During another stage of the cycle the metal oxide is regenerated and can participate in another cycle.
Reduced metal oxide + H₂O → metal oxide + H₂
Temperature and Reaction Rate
Increasing temperature increases the kinetic energy of particles and generally increases the percentage of collisions with enough energy to overcome the activation energy. The paper's primary focus is thermodynamic materials design, but reaction kinetics are also important when turning a thermodynamically possible reaction into an efficient industrial process.
Renewable Energy
The scientists are not creating energy. They are attempting to use incoming solar energy more effectively to drive an energy-demanding chemical process.
Catholic Graduate Expectation
OCSGE 7A Responsible Citizen
Hydrogen technology demonstrates why responsible citizenship requires scientists to look at the complete environmental impact of a technology. Hydrogen may be described as a clean fuel, but its environmental benefits depend strongly on how the hydrogen is produced.
Using renewable solar energy to provide energy for hydrogen production could help reduce dependence on fossil-fuel energy sources. However, scientists must also evaluate the raw materials required to build the system, its energy efficiency, durability, cost, and environmental effects.
This research reflects stewardship because scientists are attempting to use renewable energy and natural resources efficiently while developing technologies that could contribute to a more sustainable energy system.
Key Takeaway
Thermodynamics allows scientists to determine how much energy chemical reactions require and to design materials that make energy technologies more practical.