While CEA, FAU, and EPFL teams worked together at EPFL (left) to refine a scalable photocathode assembly process, HZB researchers were at DIFFER exchanging on photoanode development (right).
In PH2OTOGEN, collaboration isn’t just a concept, it's a driving force. Over the past months, the teams involved in the Hydrogen Evolving Particle and Oxidising Particle (work packages 1 and 2) have demonstrated how hands-on exchanges and shared protocols can accelerate research and create a common foundation for scaling up solar hydrogen technologies.
From isolated materials to a shared process
In the Hydrogen Evolving Particle work package (WP1), CEA, FAU, and EPFL teams joined forces in Lausanne for a collaborative session focused on developing a scalable hydrogen evolving particle assembly process. Each laboratory brought its own materials, tools, and expertise to the table, reflecting the diversity of approaches within the work package.
PH2OTOGEN deals with over a dozen materials, each with different chemistries, all of which must be stacked and integrated in a single device. The challenge: if one component fails, the whole system does not function, a reality of electrochemical systems where difficulties arise in series.
Until now, WP1 had optimised their own materials and tested subsystem performances independently. The joint session marked a turning point, as the focus shifted to collective integration and scalability. Participants explored which techniques could be used across labs, identifying scalable alternatives to lab-scale processes. One promising direction? Spray-coating, which opens up possibilities for coating larger surfaces, something few partners had explored before at this scale.
Beyond the technical progress, working together created a shared understanding. Each team left with the same procedures, the same goals, and a clearer sense of direction.
The energy and creativity that came from collaborating face-to-face was particularly energizing for the younger researchers. As Pascale Chenevier from CEA put it, "It was the perfect time to do this and we'll likely do it again next year."
The next goal: fabricating 2 cm-wide photocatalyst sheets, a step closer to real-world application.
Establishing a common language for analysis
Meanwhile, WP2 partners have focused on creating shared standards for testing and analysing the materials used on the other side of the device, the oxidising particles.
To ensure smooth collaboration across labs, partners aligned on sample sizes, testing methods, and even preferred conditions for analysis (such as pH levels and electrolyte types). This ensures that everyone’s results are comparable and consistent, no matter where the experiment was run.
A major success was the development of a shared protocol for HPLC analysis, a technique used to identify the products made during reactions. Standard methods couldn’t properly distinguish glycerol from its oxidation products, so a customised approach was co-developed, and is now used by all partners doing this type of work.
The collaboration went beyond meetings: researchers from HZB visited DIFFER to learn more about the BiVO₄ production method (SILAR), and TME and EPFL also exchanged researchers to strengthen joint work. Monthly online meetings keep everyone aligned and provide a space to share progress and solve problems together.
As the project continues, this spirit of collaboration will be key to turning innovative ideas into practical, scalable solar hydrogen solutions.
