A novel universal solution method has been proposed to prepare CuInS2 nanowire arrays (NWAs) using Cu2S NWAs as the template. The screw-like CuInS2 nanowires are constructed by many stacked nanoplates oriented along the direction of [221 1, and show diameters of 400-700 nm and lengths of several micrometres. Experimental results suggest that relatively higher In3+ concentration is beneficial to the insertion of In3+ into Cu2S to form CuInS2 with conserving the nanowire morphology. A novel exchange-erosion formation mechanism is proposed to illustrate the formation of the screw-like CuInS2 NWAs. The photoelectrochemical (PEC) performance has been investigated using the CuInS2 NWAs as photocathodes, and they exhibit double-increased photocurrent (0.3 mA cm(-2) at -0.1 V vs. RHE) compared to the pristine Cu2S NWAs, which can be ascribed to the enhanced light absorption and increased contact area for fast interfacial photocarrier separation and PEC reactions. The photocurrent has been further increased to 0.71 mA cm(-2) via decorating CdS quantum dots on the surfaces of CuInS2 nanowires. It is believed that this facile method can be generalized to prepare other copper chalcopyrite-based NWAs for highly efficient PEC water splitting. (C) 2016 Published by Elsevier B.V.