It was realized that two-dimensional layered MoS2 holds great promise as a replacement for Pt-based catalysts for hydrogen evolution reaction (HER) owing to its optimal affinity to H2. However, the synthesis and assembly of MoS2 with remarkably effective HER is still a challenge. In this work, we fabricated layered MoS2 nanosheets (NSs) on highly ordered TiO2 nanotube arrays to form MoS2/TiO2 heterostructures. The disordered MoS2 NSs expose more active sites with better HER performance. The Au deposition results in nicely patterned nanodots (NDs) on in-plane MoS2 NSs which further improves the catalytic activity due to the increased conductivity, fast electron transport and efficient charge separation. In the end, the energy required to initialize HER decreases distinctly by 170 mV and the exchange current density is as high as 71.6 μA/cm2. The Tafel slop of 72 mV/dec suggests a Volmer–Heyrovsky mechanism. Furthermore, our results demonstrate the feasibility of using Au NDs decoration to map the in-plane atomic-level defect patterns on MoS2 NSs.
