Photogenerated Electron Transfer Process in Heterojunctions: In Situ Irradiation XPS

Abstract

Photoelectron transfer between heterojuctions is an important process for photocatalysis, and identification of the electron transfer process provides valuable information for catalyst design. Herein, Ti3C2, one of the widely used two‐dimensional materials, is used to produce a heterojunction of TiO2 and Ti3C2 by an in situ growth method and the photogenerated electrons transfer between the two components for photocatalytic water splitting to hydrogen is investigated. Theoretical simulation and experimental tests proclaim that electrons transfer from Ti3C2 to TiO2 forms an internal electric field, which implies that there exists the driving force of electronic movement from TiO2 to Ti3C2. In situ irradiation X‐ray photoelectron spectroscopy shows the binding energies of TiC (in Ti3C2) and TiO (in TiO2) move toward negative and positive positions, respectively, verifying the photogenerated electrons produced from TiO2 and transferring to Ti3C2 driven by the internal electric field. In addition, the amount of TiO2 nanoparticles also affects the hydrogen evolution rate. Several parallel experiments are designed to uncover the fact that less or excess amount of TiO2 nanoparticles leads to a tinier shift of binding energy, which hints the quantity of heterojunction is a considerable factor in photocatalytic performance. This work develops a new method to directly monitor the photoelectron transfer process between heterojuctions.

Template-Free Synthesis of One-Dimensional g-C3N4 Chain Nanostructures for Efficient Photocatalytic Hydrogen Evolution

“…The UV-vis diffuse reflectance spectroscopy illustrated by Figure 3 . from the (αhv)1/2 vs. photon energy (hv) plot ( Hou et al, 2020 ; Li et al, 2020d ; Wang et al, 2020a ; Zhang et al, 2020a ; Zhang Y. et al, 2020 ), the optical bandgap of chain g-C 3 N 4 and bulk g-C 3 N 4 was calculated to be approximate 2.88 and 2.93 eV, respectively. When the particle size descends to a certain value, the electron energy level near the Fermi energy level of the metal changes from quasi-continuous to discrete energy level ( Miao et al, 2019 ; Huang et al, 2020b ; Wu et al, 2020 ; Zhang S. et al, 2020 ), and the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy level (LUMO) of the nano-semiconductor particles have discontinuous energy gap, which leads to the blue shift of the chain g-C 3 N 4 .…”

A flexible metallic TiC nanofiber/vertical graphene 1D/2D heterostructured as active electrocatalyst for advanced Li–S batteries

“…Polar transition metal oxides, on the other hand, can provide stronger affinity with LiPS from potential chemical bonding, which is thus more effective in mitigating the shuttle effect. Most of them, however, have poor electronic conductivity, which will result in sluggish reaction kinetics during the charge and discharge cycles 29–35 . The sluggish conversion kinetics in a battery cell will cause the accumulation of LiPS in its cathode and consequently gives rise to seriously uneven electrodeposition of Li 2 S, which in turn results in inhomogeneity in the transfer of electrons, being detrimental to electrochemical processes over charging and discharging 36–38 .…”

Molecular‐Level Control of the Intersheet Distance and Electronic Coupling between 2D Semiconducting and Metallic Nanosheets: Establishing Design Rules for High‐Performance Hybrid Photocatalysts

“…As plotted in Figure 2c, the shortening of the intersheet distance enhances the low‐energy component of the Ti 2p XPS features, indicating that reduction of the surface Ti species took place. [ 22 ] As summarized in Table S1, Supporting Information, peak convolution analysis clarifies the increase of the Ti 3+ /Ti 4+ ratio with a decreasing intersheet distance, verifying the controllability of the interfacial charge transfer based on the present restacking strategy. The XANES and XPS results provide strong evidence for the fine control of the interfacial electronic coupling between restacked TiO 2 and rGO NSs through variation in their interlayer distance, leading to modification of the Ti electronic structure both in the bulk and surface regions.…”