posted on 2021-03-02, 14:07authored byByung
Keun Kim, Myung Jun Kim, Jae Jeong Kim
The
activity of electrocatalysts can be improved by modifying their
electronic structures and surface morphologies. In electrochemical
reactions with gas evolution, the performance of an electrocatalyst
is also affected by how easily gas bubbles depart from an electrocatalyst
surface. However, it is difficult to quantitatively estimate the improvement
in the performance that can be achieved by promoting the departure
of gas bubbles from the electrocatalyst surface. This study investigated
the effect of surface hydrophilicity on the hydrogen evolution reaction
(HER). The water contact angles of the nickel phosphorous (NiP) films
were controlled from 40.3 to 77.2° with imperceptible differences
in their intrinsic electronic structures and surface areas. Electrochemical
analyses and in situ visualization of the gas evolution
on the NiP films indicated that an increase in the hydrophilicity
of the electrocatalysts reduced the size of gas bubbles formed on
the NiP films and shortened the duration of the bubbles’ stay
on the NiP surface. A faster gas departure enabled continuous participation
of the electrocatalyst surface in hydrogen evolution, leading to a
stable electrochemical behavior of the electrocatalyst and a decrease
in the overpotential at a given current density. A full-cell test
revealed that the enhancement of hydrogen bubble departure on a hydrophilic
NiP surface with a contact angle of 40.3° reduced the overpotential
by 134 mV at a current density of 100 mA/cm2 compared to
a more hydrophobic film with a contact angle of 77.2°.