In SituPhase Transformation on Nickel-Based Selenides for Enhanced Hydrogen Evolution Reaction in Alkaline Medium

Abstract

Identification of the active species in electrocatalysts toward hydrogen evolution reaction (HER) is of great significance for the development of the catalytic industry; however, it is still the subject of considerable controversy. Herein, we applied operando synchrotron X-ray powder diffraction (SXRD) in the NiSe 2 electrocatalyst system, and an in situ phase transformation from cubic NiSe 2 to hexagonal NiSe was revealed. The NiSe phase showed an enhanced catalytic activity. Operando Raman spectroscopy verified the decomposition of NiSe 2 during HER. Theoretical calculations suggested that the charge transfers from the Se site to Ni site during this evolution process, leading to an increased conductivity and a shifting up of d-band center, which is attributed to the enhanced activity. The generated NiSe phase acts as the "real" active species. Our work unravels the underlying phase transition of the electrocatalyst on reductive conditions in alkaline medium and highlights the significance of identifying the intrinsic active sites under realistic reaction conditions.

Engineering Bimetallic NiFe‐Based Hydroxides/Selenides Heterostructure Nanosheet Arrays for Highly‐Efficient Oxygen Evolution Reaction

“…It can be observed that, for (Ni, Fe)Se 2 /CC sample, the characteristic Raman peaks located at 132, 145, 206, and 232 cm −1 are assigned to (Ni, Fe)Se 2 . [ 35 ] But for the sample after electrodeposition, three other broaden peaks located at ≈484, 552, and 678 cm −1 appear, which are corresponding to the characteristic Raman peaks of amorphous NiFe(OH) x . [ 36 ] The XRD and Raman results show that the amorphous‐crystalline NiFe(OH) x /(Ni, Fe)Se 2 heterostructure has been successfully fabricated.…”

Hollow NiSe Nanocrystals Heterogenized with Carbon Nanotubes for Efficient Electrocatalytic Methanol Upgrading to Boost Hydrogen Co‐Production

“…During the past several years, the earth‐abundant transition metal chalcogenides (especially selenides such as NiSe, NiSe 2 , CoSe 2 ) have demonstrated their attractive efficacy for water splitting (HER and OER) as noble metal‐free electrocatalysts. [ 9–13 ] They have also been applied for the unique organic upgrading reactions due to their high electrocatalytic activity, good metallic property for promoting the electron conduction, and high selectivity for generating value‐added products. [ 14,15 ] In addition to controlling the chemical compositions of electrocatalysts, the electrocatalytic performance could be further improved by nanostructure engineering with optimized geometric features.…”

In situ growth of SeOx films on the surface of Ni–Fe–selenide nanosheets as highly active and stable electrocatalysts for the oxygen evolution reaction

“…32 They show that in the initial reaction stage of HER, the outermost layer of selenides (NiSe 2 ) will ionize in strong KOH solution, the Se 2 2will leach out and combine with the dissolved oxygen to generate SeO x , and accompanied by the generation of Ni(OH) 2 /NiOOH. 52 The specific mechanism is shown as follows: 32 (1)…”