Polyoxometalate derived p-n heterojunction for optimized reaction interface and improved HER

MoS2 is a typical electrocatalyst for hydrogen evolution reaction (HER), but the HER activity is spoilt by intensive adsorption towards H*, which requires further improvement. For n-type MoS2, the construction of p-n heterojunction with p-type MoO3 can reverse this situation, because inner electronic field in p-n heterojunction can facilitate H* desorption. Based on this hypothesis, p-n heterojunction is built between MoS2 and MoO3 with polyoxometalate compound as precursor. The obtained MoO3/MoS2 exhibits excellent HER activity, which only requires 68 mV to obtain 10 mA/cm2. With MoO3/MoS2 as cathode material and Zn slice as anode, Zn-H+ battery is assembled. Its open circuit voltage achieves 1.11 V with short circuit current 151.4 mA/cm2. The peak power density of this Zn-H+ battery reaches 47.6 mW/cm2. When discharge at 10 mA/cm2, the specific capacity and energy density reach 728 mAh/g and 759 Wh/kg. In this process, H2 production rate of Zn-H+ battery achieves 364 μmol/h with Faradic efficiency 97.8%. It realizes H2 production and electricity generation simultaneously.