In situ decorated Ni2P nanocrystal co-catalysts on g-C3N4 for efficient and stable photocatalytic hydrogen evolution via a facile co-heating method

Very recently, transition metal phosphides (TMPs) have emerged as low-cost and robust co-catalysts for decorating graphitic carbon nitride (g-C3N4) for photocatalytic hydrogen (H-2) evolution. However, to date, little work has been done regarding the decoration approaches to hybridize TMPs on the g-C3N4 surface with homogeneous dispersion and intimate interfacial contact. Herein, we present a facile and convenient route to in situ incorporate g-C3N4 nanosheets (NSs) and Ni2P nanocrystal (NC) co-catalysts via a one-step co-heating solution approach. The Ni2P/g-C3N4 (in situ) hybrid photocatalyst achieved a far superior H-2 production rate (2849.5 mmol g(-1) h(-1)) and durability (no decrease after 4 cycles of reaction within 20 h) compared to the Ni2P/g-C3N4 (self-assembly) sample. The apparent quantum yield (AQY) of 18.8% at 420 nm was also much higher than that of other TMP co-catalyst loaded g-C3N4 hybrid photocatalysts. A possible Ni(delta(+))-N(delta(-)) chemical coupling in the Ni2P/g-C3N4 (in situ) hybrid composite was proposed and corroborated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. The unique Ni(delta(+))-N(delta(-)) chemical bonding states between g-C3N4 and Ni2P significantly accelerate the photo-generated charge-carrier separation and extraction from g-C3N4, as well as maintaining the H-2 production durability. We believe that the hybridization route presented in this work will be extended to construct other TMP integrated photocatalysts toward efficient and stable solar water splitting.