Hydrogen production through the electrolytic splitting of water using photoelectrodes in photoelectrochemical cells (PEC cells) has shown promise, with energy conversion efficiencies reaching up to 19%. However, losses due to bubble formation have limited the efficiency of these devices. A team at the Institute for Solar Fuels at HZB has discovered that operating PEC cells under pressure can significantly enhance their efficiency. By pressurizing the cells to 6-8 bar, the team managed to halve energy losses, thereby potentially increasing overall efficiency by 5-10%. This improvement is attributed to the avoidance of optical scattering losses and reduction in product cross-over, particularly the transfer of oxygen. The team's multiphysics model allows for the identification of key parameters, paving the way for optimizing PEC electrolyzers. Dr. Feng Liang, the study's lead author, highlights the implications of their findings for enhancing electrochemical and photocatalytic devices, emphasizing the importance of operating within the 6-8 bar pressure range. Professor Roel van de Krol, head of the Institute for Solar Fuels, envisions the broader impact of this research in advancing sustainable hydrogen production. This breakthrough in leveraging pressure to boost green hydrogen production efficiency signifies a significant stride towards more efficient and environmentally friendly energy generation.