A new nanocatalyst, which combines the electrocatalytic activity of MoS2 nanosheets and RuS2 nanoparticles (NPs), was prepared through a safe and scalable, one-step "bottom-up" approach. It delivers high current density, with a Tafel slope of 36 mV/dec and a very small overpotential. The high exposure of MoS2 edges on the RuS2 NPs, the stronger d character of RuS2 and the electrical coupling of these two nanomaterials, grown together, were responsible for the high hydrogen production rates of 10.21/h (PEM cell 5cm x 5 cm, current density about 1.1 A/cm(2), power consumption 41.8 W, corresponding to 3.8 KWh/Nm(3) of energy consumption, efficiency 93%). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.