Experimental investigation and theoretical exploration of single-atom electrocatalysis in hybrid photovoltaics: The powerful role of Pt atoms in triiodide reduction

Although single-atom catalysts (SACs) that bridge homogeneous and heterogeneous catalysis exhibit excellent performance in various reactions, only a few examples have reported the use of SACs in electrocatalysis, especially in new types of photovoltaics. This work focused on the association between SAC Pt-1/FeOx and the electrocatalysis in hybrid photovoltaics, with the role of single-Pt atom in facilitating triiodide (I-3(-)) catalytic reduction and enhancing the conversion efficiency of dye-sensitized solar cells. Even with an extremely low dispersion density of one Pt atom per 100 nm(2) (the atomic ratio between Pt and Fe is 1: 12214), the conversion efficiency could be enhanced by 69.3% compared to bare FeOx. DFT calculation indicated that ionization potential (IP), which was responsible for the rate-determining step, decreased with the anchor of single-Pt atoms on an oxygen-terminated Fe2O3(001) slab, thereby the electron-donating ability of catalysts was enhanced. The interaction between I- and O-3(-) terminated Pt-1/Fe2O3(001) showed that charge transfer occurred mainly between I and Pt atoms. Single atom Pt played a powerful role in triiodide (I-3(-)) catalytic reduction, since its 5d orbital interacted with the support Fe2O3, accompanied with much more concentrated electronic states and higher density of the occupied states of Pt-1/Fe2O3(001) around the Fermi energy.