Innovative system turns sunlight into fuel
Solar energy is found abundantly in nature, yet a major obstacle to tap into the full potential of this energy source is that it is intermittent. For renewable energy to take hold on a larger scale, efficient and economical ways to store the Sun’s energy are needed. One of the most sustainable methods for energy storage is to directly convert water into hydrogen using sunlight. The hydrogen can then be used directly as a fuel or further processed into liquid hydrocarbons. Photoelectrochemical (PEC) water-splitting, a process where solar energy is used to break water molecules into hydrogen and oxygen, is a promising technology for hydrogen generation applications. Within the EU-funded project PECDEMO (Photoelectrochemical demonstrator device for solar hydrogen generation), researchers successfully developed a PEC system for producing hydrogen from solar power. This high-efficiency, scalable solar water-splitting device uses abundant available materials, while the integration of light absorption and electrolysis functionalities reduces the balance-of-system costs. Techno-economic analysis shows that under certain conditions, this approach can compete with coupled photovoltaic-electrolysis systems. The newly developed hybrid tandem device for solar water splitting uses a stable photoelectrode based on metal oxides as a top absorber and a high-efficiency solar cell as a bottom absorber. Stability and durability of the photoelectrodes was enhanced by functionalisation with efficient electrocatalysts, application of selective transport layers and protective coatings, and selection of suitable electrolyte solutions and operating conditions. Despite the project’s innovative system, PEC-based technology for solar water splitting is still far from becoming a commercially viable solution mainly because of the modest conversion efficiencies achieved at large scales. Moreover, fulfilling all three requirements (efficiency, stability and scalability) within a single system remains a major challenge. PECDEMO though pushed the limits for real applications and performed pioneering work, helping reveal and overcome limitation mechanisms and paving the way for future solutions based on PEC and solar cells.
Keywords
Solar energy, hydrogen, photoelectrochemical, water-splitting, PECDEMO