Economical hafnium oxygen nitride binary/ternary nanocomposite counter electrode catalysts for high-efficiency dye-sensitized solar cells

Hafnium oxygen nitride binary/ternary nanocomposites were prepared by combining Hf7O8N4, HfO2, and amorphous carbon through a simple chemical synthesis. The obtained HfO2 (Hf-R0-U), HfO2–C (Hf-R5-B), and Hf7O8N4–HfO2–C (Hf-R12-T) were characterized by XRD, SEM, FESEM, and electrochemical measurements. Dye-sensitized solar cells (DSCs) with binary Hf-R5-B and ternary Hf-R12-T composites as counter electrode (CE) showed superior electrocatalytic activity for I3− reduction and high power conversion efficiencies (PCE) of 6.71% and 7.85%, respectively, matching the performance of DSCs with Pt CE (7.19%). The design strategy demonstrated is promising for fabricating highly efficient and low-cost composite CE catalysts for DSCs.