Synchrotron Soft X‐ray Absorption Spectroscopy Study of Carbon and Silicon Nanostructures for Energy Applications

Abstract

Carbon and silicon materials are two of the most important materials involved in the history of the science and technology development. In the last two decades, C and Si nanoscale materials, e.g., carbon nanotubes, graphene, and silicon nanowires, and quantum dots, have also emerged as the most interesting nanomaterials in nanoscience and nanotechnology for their myriad promising applications such as for electronics, sensors, biotechnology, etc. In particular, carbon and silicon nanostructures are being utilized in energy-related applications such as catalysis, batteries, solar cells, etc., with significant advances. Understanding of the nature of surface and electronic structures of nanostructures plays a key role in the development and improvement of energy conversion and storage nanosystems. Synchrotron soft X-ray absorption spectroscopy (XAS) and related techniques, such as X-ray emission spectroscopy (XES) and scanning transmission X-ray microscopy (STXM), show unique capability in revealing the surface and electronic structures of C and Si nanomaterials. In this review, XAS is demonstrated as a powerful technique for probing chemical bonding, the electronic structure, and the surface chemistry of carbon and silicon nanomaterials, which can greatly enhance the fundamental understanding and also applicability of these nanomaterials in energy applications. The focus is on the unique advantages of XAS as a complementary tool to conventional microscopy and spectroscopy for effectively providing chemical and structural information about carbon and silicon nanostructures. The employment of XAS for in situ, real-time study of property evolution of C and Si nanostructures to elucidate the mechanisms in energy conversion or storage processes is also discussed.

Rapid Inversion of Surface Charges in Heteroatom‐Doped Porous Carbon: A Route to Robust Electrochemical Desalination

“…Figure d shows the XAS spectra of CDAC electrodes before and after the operation, and those of all AC electrodes used in this study are displayed in Figure S18 (Supporting Information). In all cases, four peaks were clearly apparent at around 285.3, 288.3, 292.5, and 295.6 eV, which are known as the signals from the 1s → π* electronic transition (ET) in carbon, ET at carbon bonded to heteroatoms (such as oxygen, nitrogen, or sulfur), 1s → σ* ET in carbon, and ET at fluorinated carbon (from the binder), respectively . In all the XAS spectra, the intensity of signals from the 1s → π* transition decreased after the operation, presumably due to breakage of π bonds between carbon atoms during the oxidation.…”

“…In all cases, four peaks were clearly apparent at around 285.3, 288.3, 292.5, and 295.6 eV, which are known as the signals from the 1s → π* electronic transition (ET) in carbon, ET at carbon bonded to heteroatoms (such as oxygen, nitrogen, or sulfur), 1s → σ* ET in carbon, and ET at fluorinated carbon (from the binder), respectively. [62][63][64] In all the XAS spectra, the intensity of signals from the 1s → π* transition decreased after the operation, presumably due to breakage of π bonds between carbon atoms during the oxidation. Meanwhile, no clear tendency was perceivable from the changes in the intensities of the peaks related to the 1s → σ* transition and ET at CF.…”

CuxCo1−xO Nanoparticles on Graphene Oxide as A Synergistic Catalyst for High‐Efficiency Hydrolysis of Ammonia–Borane

“…TheCK-edge XAS spectra are shown in Figure 3a.F or pure GO,t hree main absorption features can be observed and labeled as A, B, and Da t2 85.4, 288.5, and 291.7 eV, respectively.F eature Ai st ypically assigned to the p*s tates of the carbon ring structure,f eature Dt ot he s*s tates,a nd feature Btothe bonding between carbon and other elements such as C=Oa nd COOH. [13,[17][18][19][20] Forp ure GO,astrong feature Bi ndicates the heavily oxidized nature of graphene.H owever,a fter NPs decoration on GO,the XAS spectra of CuO-GO and CoO-GO show an increase in feature Ba nd ad ecrease in feature A. The increased feature Bc an be ascribed to the interfacial interaction between NPs and GO,aspreviously reported.…”

“…[13,21] Since the external bonding with the increased feature B changes the p*o rbitals of the carbon ring structure,i t typically leads to ac oncurrently decreased feature A. [19] Further,t he spectrum of CoO-GO shows al ower feature A and ah igher feature Bt han those of CuO-GO,i ndicating as tronger interfacial interaction in CoO-GO.M oreover,t he spectrum of the bimetallic Cu 0.8 Co 0.2 O-GO shows the highest feature Ba nd the lowest feature A, revealing the interfacial interaction between NPs and GO is the strongest in all the samples.C ui st he main catalytic element for AB hydrolysis (Supporting Information, Table S1), while the higher feature Bi nt he XAS spectra of CoO-GO than CuO-GO shows astronger interfacial interaction in CoO-GO than CuO-GO, indicating Co is amore effective element for the interaction. An ew feature A1 can also be observed in the spectra of the hybrid samples,but is absent in pure GO,further confirming the interfacial interaction.…”

Defective Carbon–CoP Nanoparticles Hybrids with Interfacial Charges Polarization for Efficient Bifunctional Oxygen Electrocatalysis

“…The different intensity of the absorption peaks is mainly caused by the different vacancies of unoccupied states of Co sites. Comparing to CoP bulk, the CoP–DC own stronger L 3 intensity, indicating that more vacancies existed in Co 3d states of CoP–DC, probably due to the electron transfer from the Co sites to C sites . To further verify this, the C K‐edge spectra was analyzed.…”