Hollow NiCo2Se4 microspheres composed of nanoparticles as multifunctional electrocatalysts for unassisted artificial photosynthesis

Highlights: • The NiCo₂Se₄ hollow microspheres composed of nanoparticles are prepared. • The NiCo₂Se₄ has good electrocatalytic activity on the reduction of triiodide. • The NiCo₂Se₄ is efficient for the hydrogen/oxygen evolution reactions. • The quasi-solid-state solar cells can drive overall water splitting cell. • The artificial photosynthesis device yields solar-to-hydrogen efficiency of 5.18%. Hollow NiCo₂Se₄ microspheres composed of nanoparticles are prepared using NiCo-glycerate microsphere as the sacrificial template. The NiCo₂Se₄ electrode has multiple functions, which can electrocatalyze both the reduction of triiodide in quasi-solid-state dye-sensitized solar cells (QSSDSSCs) and the overall water splitting. The hollow NiCo₂Se₄ microspheres as the electrocatalyst achieves power conversion efficiency of 8.26% for QSSDSSCs and 10 mA cm⁻² of current density at 1.85 V for the two-electrode water-splitting reaction of 0.1 mol dm⁻³ KOH aqueous solution. Three single QSSDSSCs connected in series, under 1-sun illumination, can drive the overall water-splitting device efficiently with solar-to-hydrogen efficiency of 5.18% and good stability, where the unassisted artificial photosynthesis employs only one kind of electrocatalyst.