Rational design of noble-metal-free cocatalysts for balanced H2 adsorption–desorption and accelerated charge separation toward efficient light-driven hydrogen production

Abstract

Exploiting highly active noble-metal-free cocatalysts is pivotal for practical solar-to-hydrogen conversion via photocatalytic water splitting. Herein, a hierarchical nickel phosphide nanosheet array–graphene (Ni₂P–GR) composite cocatalyst was fabricated by low-temperature phosphorization of a Ni(OH)₂–GR precursor. Using eosin Y as the visible-light photosensitizer, Ni₂P–GR exhibits exceptional H₂-evolution activity with a rate of 20 035 µmol g⁻¹ h⁻¹, significantly outperforming pristine Ni₂P, the Ni(OH)₂–GR precursor, and most reported noble-metal-free hybrid systems. Combined experimental and density functional theory studies reveal that Ni₂P–GR achieves optimized hydrogen adsorption free energy (ΔG*), lowers the hydrogen evolution reaction kinetic barrier, and establishes a favorable intermediate adsorption–desorption equilibrium. Moreover, its hierarchical architecture maximizes active-site exposure, while graphene accelerates charge separation. These merits endow Ni₂P–GR with outstanding activity and durability. This work provides a rational strategy for optimizing noble-metal-free cocatalyst composition and microstructure to boost photocatalytic H₂ production.