Top-down engineering to construct hierarchical nanocube NiS2/Ni9S8 for efficient Pt-free dye-sensitized solar cells and hydrogen evolution reaction

The triiodide reduction reaction (IRR) of dye-sensitized solar cells (DSSCs) and hydrogen evolution reaction (HER) of overall water splitting both face slow charge transfer, leading to lower efficiency. Herein, a multifunctional NiS 2 /Ni 9 S 8 nanocube electrocatalyst, exhibiting efficient power conversion efficiency and improved H∗ adsorption and desorption performance, is designed through sulfur ion exchange and fluorine ion etching NiCo prussian blue analog precursor. As a result, NiS 2 /Ni 9 S 8 with a matchable interface as counter electrode (CE), exhibits highly improved DSSC performance in I 3 − electrolyte, achieving a power conversion efficiency (PCE) of 9.31 %. This is mainly attributed to heterostructured interface of NiS 2 /Ni 9 S 8 , which modulates the electrons transfer from the Ni atom to I 3 − ions, activating the Ni-I bond and accelerating IRR. Additionally, NiS 2 /Ni 9 S 8 enhances HER performance in both acidic and alkaline electrolytes. Specifically, NiS 2 /Ni 9 S 8 nanocube shows low overpotentials of 117 mV and 111 mV at the current density of 10 mA cm −2 in 1 M KOH and 0.5 M H 2 SO 4 , respectively. This research develops noble-metal-free bifunctional electrocatalysts for clean and renewable energy conversion systems.