Since their seminal discovery in 2011,two-dimensional (2D) transition metal carbides/nitrides known as MXenes,that constitute a large family of 2D materials,have been targeted toward various applications due to their outstanding electronic properties.MXenes functioning as co-catalyst in combination with certain photocatalysts have been applied in photocatalytic systems to enhance photogenerated charge separation,suppress rapid charge recombination,and convert solar energy into chemical energy or use it in the degradation of organic compounds.The photocatalytic performance greatly depends on the composition and morphology of the photocatalyst,which,in t,are determined by the method of preparation used.Here,we review the four different synthesis methods (mechanical mixing,self-assembly,in situ decoration,and oxidation) reported for MXenes in view of their application as co-catalyst in photocatalysis.In addition,the working mechanism for MXenes application in photocatalysis is discussed and an outlook for future research is also provided.