In-situ construction defect-rich CuNiCoS4 /1T-MoS2 heterostructures as superior electrocatalysts for water splitting

•Series trimetallic sulfides with 1T-MoS2 catalysts are prepared for water splitting.•The catalysts possess numerous distortion, fracture and sulfur vacancy defects.•The proportion of 1T phase in CuNiCoS4/1T-MoS2 is more than 60 %.•The OER activity of CuNiCoS4/1T-MoS2 far exceeds RuO2 and reported catalysts.•The overall water splitting voltage of CuNiCoS4/1T-MoS2 couple lower than Pt/C//RuO.