Hollow NiCo2Se4 microspheres composed of nanoparticles are prepared using NiCo-glycerate microsphere as the sacrificial template. The NiCo2Se4 electrode has multiple functions, which can electro-catalyze 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. (C) 2018 Elsevier Ltd. All rights reserved.