An innovative tandem photoelectrochemical cell

Currently, most of the world's energy demand is met by fossil fuels, which are utilized by the industry, residential applications, and transportation sectors. However, it is widely acknowledged that these resources are not sustainable in the long run and contribute to climate change issues, such as global warming, through the emission of greenhouse gases. This has spurred an increased interest in renewable energy sources and the potential for distributed energy generation systems to replace fossil fuel-based ones. The decreasing cost of wind and solar energy and the rising price of fossil fuels have made renewable energy more appealing. Nevertheless, a major challenge with renewable energy sources is the intermittent nature of their power production, which the existing grid cannot easily handle. Hydrogen is considered a promising energy carrier that could offer an alternative approach to energy storage. Photoelectrochemical water splitting is a promising solar process for direct hydrogen production and a viable backup solution for energy storage. [1,3] A novel tandem photoelectrochemical cell utilizing low-cost and non-critical raw materials was developed to produce green hydrogen via water splitting. The photoanode is composed of a hematite-based material layered on a fluorine-doped tin oxide glass for the oxygen evolution reaction, while the photocathode is made of CuO deposited on a hydrophobic gas diffusion layer for the hydrogen evolution reaction. An anionic polymeric membrane is placed between the photo-electrodes and used as the electrolyte and gas separator, with a low crossover of hydrogen and oxygen that guarantees the operational stability of the cell and efficient separation of water-splitting products. In this context, the operational performance of the cell has been demonstrated both in elementary cells (active area 0.25 cm2) and in laboratory-scale cells (at least 5 cm2). The efficiency conversion values obtained (in elementary cells, conversion efficiency greater than 10%) are very promising, and stability tests have been carried out to demonstrate good resistance to corrosion, owing to a constant photocurrent, in the bias-assisted region. Selective hydrogen production at the photocathode output was confirmed with a mass spectrometer.