Strategic Design of a Bifunctional NiFeCoW@NC Hybrid to Replace the Noble Platinum for Dye-Sensitized Solar Cells and Hydrogen Evolution Reactions

High-performance triiodide reduction reaction (IRR) catalysts in dye-sensitized solar cells (DSSCs) and hydrogen evolution reaction (HER) catalysts in electrochemical water splitting are extremely compelling for renewable energy conversion and storage. The best IRR and HER catalysts generally rely on the use of noble metal platinum (Pt), which suffers obstacles in real-world implementation. The rational design of efficient bifunctional IRR and HER catalysts based on inexpensive and earth-abundant elements to replace scarce Pt could enable low-cost photoelectric conversion and hydrogen production but is challenging and rarely reported. Herein, we present a bifunctional NiFeCoW@NC hybrid with the unique architecture of WC loaded on the in situ formed carbon nanotubes embedded with Co-doped FeNi3 nanoparticles based on the anisotropic integration design principle, which operates efficiently for DSSCs and hydrogen evolution. The assembled DSSCs using the designed multimetal-based NiFeCoW@NC counter electrode delivered a high power conversion efficiency of 6.92% and long-term stability superior to bimetal-based NiFe@NC, CoW@NC, and Pt counterparts. It also exhibited eminent hydrogen evolution performance with a low overpotential of 127.8 mV to drive a 10 mA cm–2 current density, a Tafel slope of 60.4 mV dec–1, and satisfactory durable stability in 0.5 M H2SO4. This work provides a design principle for low-cost and highly active bifunctional catalysts to replace Pt for DSSCs and hydrogen evolution.