This study offers an in-depth examination of aluminum gallium arsenide (AlGaAs) as a high-performance and durable material for photoelectrochemical water splitting, a key method of cost-effective renewable hydrogen production. Purpose-designed pin-AlGaAs photocathodes are demonstrated to yield a remarkable photocurrent density of over 15 mA/cm2 and an impressive onset potential of 1.11 V vs RHE. These results significantly outperform those achieved with other materials, marking a considerable advancement in the field. Moreover, this work addresses the long-standing issue of AlGaAs corrosion in an aqueous electrolyte. An innovative approach using a 60 nm TiO2 protection layer is introduced, providing substantial corrosion resistance in acidic environments and thereby enhancing material durability. This research also provides valuable insights into the role of passivation layers on charge transfer. It was found that an n-GaAs passivation layer further enhances the onset potential, whereas an n-InGaP layer contributes to a decline in the overall performance. These findings pave the way for new applications of AlGaAs in solar water splitting technology, offering a promising pathway toward the development of efficient AlGaAs/Si tandem water splitting devices.
Keywords: AlGaAs; passivation; photoelectrodes; protection; solar hydrogen.