posted on 2020-03-20, 14:48authored bySeongbeen Kim, Changhyeok Choi, Jongkook Hwang, Jinkyu Park, Jooyoung Jeong, Hyunwoo Jun, Seonggyu Lee, Soo-Kil Kim, Jong Hyun Jang, Yousung Jung, Jinwoo Lee
To
overcome inherent limitations of molybdenum carbide (MoxC) for hydrogen evolution reaction (HER), i.e., low density of active site and nonideal hydrogen binding
strength, we report the synthesis of valence-controlled mesoporous
MoxC as a highly efficient HER electrocatalyst.
The synthesis procedure uses an interaction mediator (IM), which significantly
increases the density of active site by mediating interaction between
PEO-b-PS template and Mo source. The valence state
of Mo is tuned by systematic control of the environment around Mo
by controlled heat treatment under air before thermal treatment at
1100 °C. Theoretical calculations reveal that the hydrogen binding
is strongly influenced by Mo valence. Consequently, MoxC achieves a significant increase in HER activity
(exceeding that of Pt/C at high current density ∼35 mA/cm2 in alkaline solution). In addition, a volcano-type correlation
between HER activity and Mo valence is identified with various experimental
indicators. The present strategies can be applied to various carbide
and Mo-based catalysts, and the established Mo valence and HER relations
can guide development of highly active HER electrocatalysts.