Graphitic C₃N₄ modified by Ni₂P cocatalyst: An efficient, robust and low cost photocatalyst for visible-light-driven H₂ evolution from water

The development of an efficient, robust and low cost catalyst for photocatalytic H₂evolution is an uphill challenge and has attracted plenty of researchers’ interest. Herein, we report g-C₃N₄/Ni₂P composite photocatalyst for H₂evolution reaction in which Ni₂P acts as a noble-metal-free cocatalyst for g-C₃N₄. The g-C₃N₄/Ni₂P is prepared based on two-step hydrothermal and phosphidation method. The optimum H₂evolution ability is obtained when the loaded weight percent of Ni₂P is 0.48% (g-C₃N₄/Ni₂P-0.48%), along with a corresponding H₂evolution rate of 5.67 μmol h⁻¹. This value is about 1418 times more than pure g-C₃N₄and obviously higher than that of Pt modified g-C₃N₄(3.78 μmol h⁻¹). In addition, the g-C₃N₄/Ni₂P-0.48% catalyst demonstrates almost negligible photocatalytic degradation capability even after eight repeated cycles (a reaction time of 12 h per cycle). The introduction of Ni₂P cocatalyst significantly accelerates the separation and transfer of photogenerated electrons of g-C₃N₄, hence resulting in enhanced H₂evolution efficiency. In addition, the Ni and P in Ni₂P cocatalyst act as the hydride-acceptor and proton-acceptor centers, respectively, which synergistically facilitate the fast generation of H₂.