The crystalline/amorphous contact in Cu2O/Ta2O5 heterostructures: increasing its sunlight-driven overall water splitting efficiency

Water splitting using heterostructures without external bias or sacrificial agents is promising for solving the energy crisis. However, the heterostructures with appropriate band alignments and band gaps have always shown certain degrees of lattice and electron mismatches at their interfaces, which make it difficult for these heterostructures to achieve the theoretically maximum sunlight-driven overall water splitting activity. Here, we made a new type of heterostructure-a crystalline Cu2O/amorphous Ta2O5 heterostructure instead of one with a crystalline/crystalline contact at the interface-which was found to perform overall water splitting with a high apparent quantum yield under visible light irradiation. The results revealed the crystalline/amorphous contact to have a great potential for allowing heterostructures to be used effectively for sunlight-driven overall water splitting.