Unraveling surface polarization in hydrothermally derived AgFeO2 nanosheets for enhanced photoelectrochemical performance†

This study conducts a comprehensive exploration of the synthesis and photoelectrochemical performance of delafossite AgFeO₂ nanosheets modulated by controlled hydrothermal conditions. The dimensions of the nanosheets, namely width and exposed area, are adjusted to examine the impact of surface polarization on photocatalytic efficiency. Notably, an increase in nanosheet width while keeping the thickness constant corresponds to a significant rise in photocurrent density. Under optimized conditions, AgFeO₂ nanosheets with smaller thickness and larger surface area of the (001) facet reach a peak photocurrent density of 15.6 μA cm⁻². This enhancement is attributed to the increased intensity and contribution of the built-in electric field on the (001) polar facet, thereby facilitating improved effective separation and rapid transfer of photogenerated electron–hole pairs. In brief, regarding the surface polarization effect of AgFeO₂ nanosheets, a smaller thickness leads to a stronger built-in electric field intensity generated by the surface polarization effect, while a larger exposed area makes a more significant contribution to the surface polarization effect. Therefore, to fully utilize the surface polarization effect, it is essential to carefully and precisely control the morphology and size of AgFeO₂ nanosheets during the preparation process. Moreover, the introduction of interstitial oxygen and an external magnetic field further demonstrates the potential of multiple polarization coupling—spin, macro, and surface—to maximize the photoelectrochemical potential of AgFeO₂ nanosheets. These findings emphasize the crucial role of surface polarization in optimizing the photoelectrochemical performance of AgFeO₂ nanosheets and highlight the potential of nanoscale design in developing advanced photocathodes. The findings open up avenues for future research aimed at refining synthesis methods and exploiting the synergistic effects of multiple polarizations for enhanced solar energy conversion efficiencies.