A quantitative study of valence electron transfer in the skutterudite compound CoP₃by combining x-ray induced Auger and photoelectron spectroscopy

Abstract

We use the sum of the ionization and Auger energy, the so-called Auger parameter, measured from the x-ray photoelectron spectrum, to study the valence electron distribution in the skutterudite CoP(3). The electron transfer between Co and P was estimated using models relating changes in Auger parameter values to charge transfer. It was found that each P atom gains 0.24 e(-), and considering the unit formula CoP(3) this is equivalent to a donation of 0.72 e(-) per Co atom. This is in agreement with a recent electron energy-loss spectroscopy study, which indicates a charge transfer of 0.77 e(-)/atom from Co to P.

Stability of CoPx Electrocatalysts in Continuous and Interrupted Acidic Electrolysis of Water

“…XPS analysis of the Co 2p spectral region reveals the formation of a dominant P‐rich CoP x phase (BE(Co 2p 3/2 )=778.2±0.2 eV) in which Co is assumed to be mostly covalently bound to P with corresponding charges δ + (∼1+) and δ − (∼1−), respectively (Figure a) . The small shoulder at higher binding energies (BE(Co 2p 3/2 ) >779.6 eV) is most likely attributed to a native oxide formed on the surface of CoP x upon air exposure.…”

Evaluating the Stability of Co2P Electrocatalysts in the Hydrogen Evolution Reaction for Both Acidic and Alkaline Electrolytes

“…The evident compositional changes of the Co 2 P@CP were further analyzed by X-ray photoelectron spectroscopy (XPS). As shown in Figure a, the Co 2p spectra of the fresh sample (black solid line) reveal a dominant component at BE­(Co 2p 3/2 ) = 778.9 eV, corresponding to Co δ+ (0 < δ < 1) , covalently bound to P in cobalt phosphide Co 2 P. , The shoulder at higher binding energy (780.6 eV) is attributed to the asymmetric plasmon loss of metal phosphides , and possible cobalt oxide species as a result of sample exposure to air. ,, After stability testing in acid, the Co 2p 3/2 peaks remain almost unchanged. In contrast, significant changes are observed after the stability test in alkaline electrolyte: the peak assigned to Co δ+ decreases substantially, while the intensity of the component at BE­(Co 2p 3/2 ) = 780.6 eV assigned to oxidic Co increases.…”

“…The P 2p XPS spectra show two main peaks at binding energies of 129.6 and 130.5 eV (ratio 2:1), corresponding to the spin–orbit split doublet of phosphide 2p 3/2 and 2p 1/2 lines, respectively. ,,,− The doublet at BE­(P 2p 3/2 ) = 131.1 eV and BE­(P 2p 1/2 ) = 131.9 eV is attributed to elementary P as a remainder from thermal phosphidization treatment. , The doublet at 132.8 and 133.6 eV and the doublet at 134.2 and 135.1 eV are attributed to orthophosphate − and metaphosphate, , respectively. The phosphate components may result from either surface oxidation upon air exposure or residues from thermal decomposition of NaH 2 PO 2 .…”

Fluorinated Artificial Solid–Electrolyte–Interphase Layer for Long-Life Sodium Metal Batteries

“…Our observations regarding the SEI protection layer on Na constraining its volume expansion and preventing Na dendrite formation and growth align well with recent research in the field. 58,59 A conductive layer composed of NaxSn alloys and NaF, created by using a unique solution dropping technique, has been shown to substantially suppress Na dendrite formation and reduce interfacial resistance. The implications of this discovery go beyond enhancing the wettability of Na metal, promoting charge transfer kinetics, and ensuring the uniform distribution of local current density.…”