Abstract
The surface reconstruction behavior of transition metal phosphides
(TMPs) precursors is considered an important method to prepare efficient
oxygen evolution catalysts, but there are still significant challenges
in guiding catalyst design at the atomic scale. Here, the CoP nanowire
with excellent water splitting performance and stability is used as a
catalytic model to study the reconstruction process. Obvious double
redox signals and valence evolution behavior of the Co site are
observed, corresponding to Co2+/Co3+and Co3+/Co4+ caused by
auto-oxidation process. Importantly, the in-situ Raman spectrum exhibits
the vibration signal of Co-OH in the non-Faradaic potential interval for
oxygen evolution reaction, which is considered the initial
reconstruction step. Density functional theory and ab initio molecular
dynamics are used to elucidate this process at the atomic scale: First,
OH- exhibits a lower adsorption energy barrier and
proton desorption energy barrier at the configuration surface, which
proposes the formation of a single oxygen (-O) group. Under a higher -O
group coverage, the Co-P bond is destroyed along with the
POx groups. Subsequently, lower P vacancy formation
energy confirm that the Ni-CoP configuration can fast transform into
highly active phase. Based on optimized reconstruction behavior and
rate-limiting barrier, the Ni-CoP exhibit an excellent overpotential of
236 mV for OER and 1.59 V for overall water splitting at 10 mA
cm-2, which demonstrates low degradation (2.62 %)
during the 100 mA cm-2 for 100 h. This work provide
systematic insights into the atomic-level reconstruction mechanism of
TMPs, which benefit further design of water splitting catalysts.