Atomic Layer Deposition of Hafnium(IV) Oxide on Graphene Oxide: Probing Interfacial Chemistry and Nucleation by using X‐ray Absorption and Photoelectron Spectroscopies

Abstract

Interfacing graphene with metal oxides is of considerable technological importance for modulating carrier density through electrostatic gating as well as for the design of earth-abundant electrocatalysts. Herein, we probe the early stages of the atomic layer deposition (ALD) of HfO on graphene oxide using a combination of C and O K-edge near-edge X-ray absorption fine structure spectroscopies and X-ray photoelectron spectroscopy. Dosing with water is observed to promote defunctionalization of graphene oxide as a result of the reaction between water and hydroxyl/epoxide species, which yields carbonyl groups that further react with migratory epoxide species to release CO . The carboxylates formed by the reaction of carbonyl and epoxide species facilitate binding of Hf precursors to graphene oxide surfaces. The ALD process is accompanied by recovery of the π-conjugated framework of graphene. The delineation of binding modes provides a means to rationally assemble 2D heterostructures.

Engineering the Coordination Environment of Single Cobalt Atoms for Efficient Oxygen Reduction and Hydrogen Evolution Reactions

“…The peaks at 398.4, 399.4, and 410.1 eV are assigned to the π* states of pyridinic N (a), pyrrolic N (b), and graphitic-type N (c) species, respectively, and the peak at approximately 407.0 eV (d) is the characteristic signal of the σ* state for C–N (Figure B). , Moreover, the intensity of the peak attributed to pyridinic N (398.4 eV) is obviously greater than those of the peaks attributed to pyrrolic N (399.4 eV) and graphitic-type N (410.1 eV), which suggests that N in S-Co/N/C and Co/N/C mainly consists of pyridinic-type N species. S K-edge spectra for S-Co/N/C and Co/S/C present similar curves with the main peak centered at 2473 eV (Figure S5), quite consistent with those of the reference materials. , In the XPS C 1s spectra, C1 (284.6 eV), C2 (285.6 eV), C3 (286.7 eV), and C4 (288.5 eV) are ascribed to sp 2 -C, sp 3 -C, C–O and O–CO species, respectively. ,, The C3 and C4 species are essentially nonexistent in S-Co/N/C, Co/N/C, and Co/S/C, which again supports that O species in the graphene support were removed upon heat treatment (Figure C, Figure S6, and Table S1). The N 1s spectra are deconvoluted into three species (pyridinic N (N1), pyrrolic N (N2), and graphitic-type N (N3)), ,,, as shown in Figure D.…”

“…The chemical features of the Co-based catalysts were revealed by X-ray absorption spectroscopy (XAS), consisting of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra, and X-ray photoelectron spectroscopy (XPS) (Figure ). The peaks at approximately 285.4 and 292.5 eV are attributed to the unoccupied π* and excited σ* states in graphene, respectively. ,− In comparison to the Co/O/C material, the two peaks at 287.4 and 288.9 eV belonging to C–O and CO species, , respectively, disappear in S-Co/N/C, Co/S/C, and Co/N/C, which indicates that O species were removed upon heat treatment and GO was reduced to graphene (Figure A). This result is solidly supported by the XRD results (Figure S2).…”

Acetylenedicarboxylate and In Situ Generated Chlorofumarate-Based Hafnium(IV)–Metal–Organic Frameworks: Synthesis, Structure, and Sorption Properties

“…The deconvoluted Hf spectrum shows two peaks at 17.8 and 19.5 eV binding energy, corresponding respectively to 4f 7/2 and 4f 5/2 components of hafnium in the oxidation state Hf IV . 31 Fitting the C 1s spectrum reveals three components which can be assigned to the carboxylate's carbon −COO (289.4 eV), the chlorine-bonded olefinic carbon C−Cl (285.2 eV) and the hydrogen-bonded olefinic carbon C−H (283.3 eV). The high-resolution O 1s spectrum (Figure 4) shows two components attributable to the carboxylate oxygen C−O (530.5 eV) and the oxygen of the hafnium cluster Hf−O (530.8 eV).…”

“…These results prove occurrence of a hydrochlorination (addition of HCl) on the ADC triple bond to a chlorofumarate containing MOF. The deconvoluted Hf spectrum shows two peaks at 17.8 and 19.5 eV binding energy, corresponding respectively to 4f 7/2 and 4f 5/2 components of hafnium in the oxidation state Hf IV . Fitting the C 1s spectrum reveals three components which can be assigned to the carboxylate’s carbon −COO (289.4 eV), the chlorine-bonded olefinic carbon C–Cl (285.2 eV) and the hydrogen-bonded olefinic carbon C–H (283.3 eV).…”

Investigating the Nucleation of AlOx and HfOx ALD on Polyimide: Influence of Plasma Activation

“…The nucleation of ALD processes has been commonly studied by characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ellipsometry, quartz microbalance (QCM), both in and ex situ, but has also been investigated using other techniques such as atomic force microscopy (AFM), scanning tunneling microscopy (STM), X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Auger electron spectroscopy (AES), or low energy ion scattering (LEIS) [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71]. Each technique has its own advantages and disadvantages.…”