Gradient porous electrode-inducing bubble splitting for highly efficient hydrogen evolution

Designing highly efficient electrodes for the hydrogen evolution reaction (HER) has attracted enormous attention owing to the urgent demand to decrease greenhouse gas emissions. However, the enormous energy loss due to an insufficient exposure of active sites caused by sluggish bubble detachment has been proven to be a critical obstacle for further enhancing the HER performance. In this study, we developed a gradient porous electrode (SML-LMS-HE) with decreasing pore size from the middle of the electrode to the two sides. This electrode was fabricated by simply pressing stack-up gradient porous nickel foams and employing a solvothermal treatment to load hierarchically porous coral-shaped MoS2/Ni3S2 heteronanorod electrocatalysts. The as-prepared SML-LMS-HE electrode enabled a much smaller hydrogen bubble detachment size by inducing hydrogen bubble splitting as compared to another gradient porous electrode and homogeneous porous electrode, leading to a reduced reactant transfer resistance and a decreased ohmic drop within the electrode. As a result, SML-LMS-HE exhibited excellent HER activity with an overpotential as low as 83 mV at − 10 mA cm−2 and prominent durability.