The Tafel analysis in Figures and shows that the Tafel slope of MoS 2 @NiFeCo-Mo(doped)-LDH is as low as 95 mV dec -1 . This is significantly lower than those of NiFeCo-Mo(doped)-LDH (139 mV dec -1 ), MoS 2 @NiFeCo-LDH (175 mV dec -1 ), and NiFeCo-LDH (161 mV dec -1 ). Under light illumination the Tafel slope of MoS 2 @NiFeCo-Mo(doped)-LDH is further decreased from 95 mV dec -1 to 65 mV dec -1 . These Tafel slopes are rather close to those of commercial Pt/C (49 mV dec -1 ). The Tafel slopes suggest that the HER on MoS 2 @NiFeCo-Mo(doped)-LDH likely follows the Volmer-Heyrovsky mechanism with the Heyrovsky step as the rate-determining step (RDS). The spread of the Tafel slopes between different materials is, however, rather significant, which indicates that the HER mechanism may involve different RDSs and that the current density may depend e.g. on the mass transfer efficiency.