The overpotentials at 10 and 50 mA cm -2 HER current densities under light irradiation and dark conditions are shown in Figure -12 of the Supporting Information. Table compares the HER performance of MoS 2 @NiFeCo-Mo(doped)-LDH with other recently developed catalysts and shows that the hierarchical MoS 2 @NiFeCo-Mo(doped)-LDH heterostructure exhibits very high electrocatalytic HER activity; under dark conditions at 10 mA cm -2 the overpotential of MoS 2 @NiFeCo-Mo(doped)-LDH is 102 mV, which is only marginally higher than that of the Pt/C benchmark (73 mV) (Figure ). Under light irradiation, the MoS 2 @NiFeCo-Mo(doped)-LDH photoelectrode exhibits an overpotential of 61 mV at a current density of 10 mA cm -2 . Overall, the results in Figure -12 clearly show that i) the deposition of MoS 2 QDs increases the (photo)electrocatalytic HER activity more on NiFeCo-Mo(doped)-LDH than on NiFeCo-LDH and ii) Mo doping and MoS 2 significantly improve the electrocatalytic HER activity as compared to the NiFeCo-LDH.