Boosting and regulating solar energy conversion performance of delafossite AgFeO2 by spin polarization

Abstract

Spin polarization plays an important role in spintronics, nanoelectronics, new energy, and other emerging high-tech fields. However, due to the lack of suitable research targets and insufficient understanding of the fundamental effects and regulation strategies, the application of spin polarization in solar energy conversion materials and devices is still a huge challenge. Herein, we choose delafossite AgFeO₂ as our research objective, which has an outstanding polytype feature and can be applied to hydrogen production via photocatalytic and photoelectrochemical water-splitting. Through a combination of co-precipitation and hydrothermal methods, we controllably prepared delafossite AgFeO₂ samples with different crystal phases (including the 3R phase, 2H phase and 3R–2H mixed phase). The experimental measurements and theoretical calculations show that the three as-prepared delafossite AgFeO₂ samples are very similar in their fundamental physicochemical properties except for their significantly different spin polarization and ferromagnetism. The results of the hydrogen production tests via photocatalytic water-splitting and photocurrent density indicate that the as-prepared AgFeO₂ sample with the 3R phase shows the largest spin polarization intensity and the most prominent solar energy conversion performance. Moreover, under an external magnetic field, its solar energy conversion performance is greatly improved. These findings demonstrate that spin polarization is the key factor determining the solar energy conversion efficiency of delafossite AgFeO₂, which can be boosted and regulated by the crystal phase and external magnetic field.