A highly stable non-noble metal Ni₂P co-catalyst for increased H₂ generation by g-C₃N₄ under visible light irradiation

Nickel phosphide (Ni₂P) was grown on a graphitic carbon nitride (g-C₃N₄) surface by annealing a mixture of g-C₃N₄, NiCl₂, and NaH₂PO₂ at 400 °C for 2 h in an Ar atmosphere. During the annealing, Ni₂P particles formed intimate interfaces with g-C₃N₄. As a result, charge transfer from photo-excited g-C₃N₄ to Ni₂P was improved as demonstrated by the improved photocatalytic H₂ generation (40.5 μmol h^-1 g^-1) compared to a physical mixture of Ni₂P and g-C₃N₄ (trace H₂ generation). Under optimal and identical experimental conditions, the H₂ production rate on Ni₂P-loaded g-C₃N₄ (2 wt%) is 82.5 μmol h^-1 g^-1, which is higher than that of Pt-loaded g-C₃N₄ (0.5 wt%) (72 μmol h^-1 g^-1). Impressively, Ni₂P shows a highly stable H₂ production activity despite being a non-noble metal co-catalyst. No activity loss occurs over repeated use and 24 h long-term H₂ generation trials. In contrast, a pronounced reduction in H₂ generation was observed for Pt-loaded g-C₃N₄ (0.5 wt%) over the same 24 hour trial period. Among their many advantages, including non-toxicity, low cost and natural abundance, Ni₂P/g-C₃N₄ composites are a promising alternative for realizing efficient, long-lasting photocatalytic H₂ production.