Photocatalytic H₂ production and photocatalytic decomposition are efficient and economical methods to obtain hydrogen fuel and dispose of organic pollutants. In this paper, amorphous nickel phosphide (Ni₂P) is synthesized by an extremely simple precipitation method under low temperature. The prepared nickel phosphide was not only used to produce H₂ in the presence of Eosin Y as sensitizer and triethanolamine (TEOA) as a sacrificial electron donor but also to degrade 4-nitrophenol under visible light illumination. The rate of hydrogen evolution is 34.0 μmol h⁻¹ g⁻¹ and the degradation efficiency is 25.5% within 4 h at initial 5.0 mg L⁻¹ 4-nitrophenol. Probable photocatalytic mechanisms were discussed. The present work is expected to contribute toward the hydrogen evolution and disposal of highly toxic pollutants by cost-effective photocatalytic means.