Researchers from the Vrije Universiteit Brussel and partners have mapped how emerging chalcogenide semiconductor absorbers behave in photoelectrochemical systems that convert sunlight and CO2 into chemical fuels. They investigated how the electronic band structure of these materials controls the generation, separation and transfer of charge at the semiconductor-electrolyte interface, and how these processes limit device efficiency over time.
The team focused on using non-toxic, Earth-abundant compounds as light absorbers, with the aim of replacing critical or scarce elements in solar fuel architectures. By examining the band positions and internal electric fields, they identified how the absorber layers electronically couple to underlying contacts and to the catalyst-electrolyte side, clarifying which configurations promote efficient charge extraction.
Using detailed measurements, the researchers linked changes in the photoresponse to specific degradation pathways in the absorbers and interfaces. This allowed them to determine how defects, surface conditions and interfacial reactions affect long-term stability, and which material treatments improve durability under operating conditions.
The research also shows that adding custom electrocatalysts to the reactive interfaces improves the overall performance of the device. These catalysts facilitate the desired redox reactions and help maintain the activity of the semiconductor over many operating cycles, extending its operational life without relying on scarce elements.
According to first author Beatriz de la Fuente, the work shows that solar fuel systems can be constructed from materials that are both widely available and compatible with environmental and safety restrictions. “Our findings show that it is possible to build solar fuel systems with abundant, environmentally friendly materials that are both efficient and sustainable,” says Beatriz de la Fuente. “This is a crucial step in turning CO2 from a problem into a valuable resource.”
The results support the development of integrated photoelectrochemical devices that use CO2 as a feedstock for fuel production instead of as a waste stream. In the short term, insights into band structure, interfaces and catalyst coupling provide guidance for designing scalable systems, while in the longer term such devices can be deployed as decentralized units that produce solar fuels and contribute to climate and energy goals.
The work was carried out within the SUME group (Sustainable Materials Engineering) at the VUB in collaboration with Stanford University, University of Antwerp and University of Hasselt. It is part of SYNCAT (SYNergetic Design of CATalytic Materials for Integrated Photo and Electrochemical CO2 Conversion Processes), a multi-university project funded through the Flemish Moonshot Initiative (Strategic Basic Research for Clusters) of VLAIO, with additional support from the Flanders Scientific Research Fund (FWO).
Research report:Investigating the electronic band structure of emerging chalcogenide absorbers for photoelectrochemistry
