Dispositivo di scissione di acqua determinante da luce per la generazione di idrogeno solare e metodo per la fabbricazione dello stesso

As of 2020, 95% of the hydrogen is produced from fossil fuels by steam reforming (grey) or coal gasification (brown). These processes result in 10 kg of carbon waste per kg of hydrogen produced. Blue hydrogen has a lower carbon print due to the capture of 80-90% of the CO2 produced. However this process is not 100% carbon-free and suffers from the added step to capture and store the CO2. Hydrogen can be produced by alkaline water electrolysis or protone exchange membrane electrolysis. These processes require high applied overvoltages, components that can resist to harsh alkaline/acidic environments and rare and expensive catalysts such as Pt, Ir or Ru. Another approach is the use of solar energy to split water into hydrogen and oxygen. Currently, the two main routes pursued for solar hydrogen generation are based on (i) wide-bandgap metal oxides or III-V semiconductors used as photoelectrodes for direct photoelectrochemical water splitting; and (ii) photovoltaic cells for catalyst-assisted water electrolysis. These technologies ideally do not require the aid of an external bias, however they both suffer from poor efficiency levels and limited resistance to degradation. These approaches often request the use of expensive co-catalysts.

This novel InGaN/InN photo-anode promotes the direct conversion of white light into zero-impact hydrogen. The InGaN layer can be grown directly on economically viable Si substrates via Molecular Beam Epitaxy (MBE). InGaN exhibits high resistance to degradation and wide bandgap tunability, thus making it optimal candidate for photocatalysis applications. The electrode is submerged in water and exposed to white light. The InGaN layer can absorb the optimal amount of solar radiation to promote the oxidation of water into O2 without any energy dispersion. The photocurrent generated inside the semiconductor drives the electrons to the working counter-electrode, on the surface of which H2 is produced. InN quantum dots can be grown in-situ directly on the InGaN surface via MBE. The quantum dots can enhance the electrode efficiency by 50% compared to bare InGaN. InGaN/InN properties alone allow to drive photo-electrochemical water splitting with almost 10% efficiency without an external voltage or the addition of a co-catalyst that could reduce the radiation adsorption. The electrode can be directly integrated into a commercial solar cell to obtain a high stability and high efficiency autonomous system. The technology can be developed onto wide or flexible surfaces and easily introduced as a photocatalytic stage into traditional systems where the catalytic bias is provided by external photovoltaic cells.

The product which forms the base of the business is an InN/InGaN quantum dot photoanode for solar hydrogen generation by water splitting which can be integrated with a commercial Si photovoltaic cell to form a hybrid device with maximized efficiency. The plan is to produce the photoanode and deliver it to established companies for full system fabrication. Future planning regards (i) the integration of the photoelectrode with a commercial Si solar cell which can boost the efficiency of a fully autonomous system (ii) the transfer to mass production technologies like metal organic vapor phase epitaxy.