One-pot synthesis of array-like sulfur-doped carbon nitride with covalently crosslinked ultrathin MoS2 cocatalyst for drastically enhanced photocatalytic hydrogen evolution

•One-pot method was used to synthesize covalent cross-linking photocatalyst of ultrathin MoS2 and sulfur-doped carbon nitride (MS/SCN-x%).•The MS/SCN hybrids have ultrathin lamellar structure and the nanosheets are arranged in an array-like structure.•The UV–vis absorption spectra of MS/SCN hybrids have two noticeable shoulder, proving MoS2 has an ultrathin structure.•The introduction of cyano group in SCN can enhance the visible light absorption capacity and help to improve the photocatalytic reaction.•The MS/SCN-2.5% hybrids drastically improved HER performance, over original MoS2 nanosheet modified SCN, also rivaled with Pt/SCN..