Size Effects of MoS2 on Hydrogen and Oxygen Evolution Reaction

Molybdenum disulfide (MoS2) has been widely used as a catalyst for the bifunctional activities of hydrogen and oxygen evolution reactions (HER and OER). Here, we investigated size dependent HER and OER performance of MoS2. The smallest size (90 nm) of MoS2 exhibits the lowest overpotential of −0.28 V at −10 mAcm−2 and 1.52 V at 300 mAcm−2 with the smallest Tafel slopes of 151 and 176 mVdec−1 for HER and OER, respectively, compared to bigger sizes (2 μm and 6 μm) of MoS2. The better HER and OER performance is attributed to high electrochemical active surface area (6 × 10−4 cm2) with edge sites and low charge transfer resistance (18.1 Ω), confirming that the smaller MoS2 nanosheets have the better catalytic behavior.