@article{Wu2025, 
author = {Chengqi Wu and Jiaqi Liu and Yiwei Tan},
title = {Transition metal sulfides in alkaline hydrogen evolution electrocatalysis: Re-exploring their structure and composition evolution and its correlation with activity},
year = {2025},
journal = {Nano Research},
volume = {18},
number = {3},
pages = {94907240},
keywords = {hydrogen evolution reaction, alkaline water electrolysis, transition metal sulfides, amorphous structures, metal hydroxy salts, Pourbaix diagrams},
url = {https://www.sciopen.com/article/10.26599/NR.2025.94907240},
doi = {10.26599/NR.2025.94907240},
abstract = {Herein, the activity and stability evolution of transition metal sulfides used as electrocatalysts for alkaline hydrogen evolution reaction (HER) are studied during a prolonged HER period. We have thoroughly characterized and analyzed the composition and structure of NiV2S4, NiS, Ni3S2, and VS2 prior to HER and after the HER for 2–20 h at a constant current density of −100 mA·cm−2. It is found that all these metal sulfides in KOH electrolyte are gradually degraded to the corresponding amorphous metal hydroxy salts/oxysulfides (i.e., a-KNi(OH)3/a-NiOxSy and a-KV(OH)6/a-VOxSy) and finally to amorphous metal hydroxy salts/oxides (i.e., a-KNi(OH)3 and a-KV(OH)6/a-V2O3) from surface to bulk with elongating HER time. Concomitantly, the morphologies of the derived metal hydroxy salts/oxysulfides (oxides) are significantly different from the corresponding metal sulfide precursors, especially those containing metal ions (for example, V3+ in NiV2S4 and Ni+ in Ni3S2) in intermediate valence states due to the modification of chemical bonds to an extensive extent invoked by their capability of facilely accepting and donating electrons. This stability and structural evolution of these metal sulfides are substantiated by the calculated Pourbaix diagrams of Ni-S-H2O and Ni-V-S-H2O systems. After the HER at −100 mA·cm−2 for 20 h, compared to the corresponding pristine metal sulfides, the apparent HER activities of all the derived metal hydroxy salts/oxide decrease due to the diminution of their electrochemically active surface areas (ECSAs). On the contrary, their specific activities increase due to the enriched structural defects caused by the amorphous structures and changes in valence state of the metal ions.}
}