MOFs-derived bifunctional Ni-Fe-Mo sulfide electrode catalysts with hollow bipyramidal structures for efficient photovoltaics and hydrogen generation

• Hollow bipyramidal Ni-Fe-MoS x was synthesized by a template conversion process. • (NH 4 ) 2 MoS 4 was used to react with Ni-Fe LDH to form a hollow structure. • Ni-Fe-MoS x had large surface area and high catalytic activity for HER. • The PCE of Ni-Fe-MoS x (9.37%) for DSSC was much higher than that of Pt (8.12%). The effective improvements in structure and composition are critical to the performances of inexpensive electrocatalysts based on transition metal chalcogenides (TMCs), especially in dye-sensitized solar cell (DSSC) and hydrogen evolution reaction (HER), which will be an ongoing challenge. Herein, a novel method of forming Ni-Fe-Mo sulfide composite electrocatalyst (denoted as Ni-Fe-MoS x ) by adding molybdenum element when modifying the active sites on the surface of Ni-Fe layered double hydroxide (Ni-Fe LDH) was proposed and studied. Beginning with MIL-88A (Fe), Ni-Fe LDH was prepared by the hydrolysis of nickel and iron ions in alkaline solution, and then vulcanized by ammonium tetrathiomolybdate to synthesize Ni-Fe-MoS x electrocatalyst with hollow bipyramidal structure and rich active sites on the modified surface. Benefiting from the advantages of hollow construction and the enhanced intrinsic activity of more active sites, Ni-Fe-MoS x electrode delivered an outstanding power conversion efficiency (PCE) of 9.37% in DSSC. Accompanying with a low onset potential of 30.4 mV, its stability in acid HER could maintain well over long periods of time. The successful implementation of the scheme is expected to provide a novel avenue for synthesizing bifunctional electrocatalysts based on TMCs.