Regulating Crystal Structure and Atomic Arrangement in Single-Component Metal Oxides through Electrochemical Conversion for Efficient Overall Water Splitting

Abstract

Single-component transition-metal oxide (TMO: FeOx, NiOx, or CoOx) nanosheets grown on nickel foam (NF) were electrochemically optimized with Li ion (Na ion)-induced conversion reaction for bifunctional electrocatalysis. The optimum FeOx/NF-Li electrocatalyst exhibits low overpotentials of 239 mV for hydrogen evolution reaction and 276 mV for oxygen evolution reaction at a current density of 100 mA cm–2. A two-electrode water splitting cell using FeOx/NF-Li as both anode and cathode requires only 1.60 V to achieve a current density of 10 mA cm–2. The impressive water splitting performance of the FeOx/NF-Li electrode is revealed to be attributed to Li-induced electrochemical conversion, which alters the crystal structure, creating more active sites for electrocatalytic reactions, as well as introduces O vacancies increasing the electron density and the intrinsic conductivity. More importantly, the atomic arrangement is regulated from tetrahedral Fe­(Td) to octahedral Fe­(Oh) coordination, which acts as catalytically active sites with reduced Gibbs free energy for the rate-determining steps. This electrochemical conversion reaction can be extended to other TMOs (i.e., NiOx/NF and CoOx/NF) for promoted electrocatalytic water splitting performances. This study provides an in-depth understanding on the nature of atomic and electronic structure evolution to promote the electrocatalytic activity.

Role of Interfacial Defects in Photoelectrochemical Properties of BiVO4 Coated on ZnO Nanodendrites: X-ray Spectroscopic and Microscopic Investigation

“…The transmitted beam intensities were measured at the image pixels. More details concerning STXM measurements and analysis are available elsewhere. , The STXM data were obtained by principal component analysis by clustering using the aXis2000 program (free for noncommercial use at ) and PCA_GUI (freeware from ).…”

“…More details concerning STXM measurements and analysis are available elsewhere. 31,32 The STXM data were obtained by principal component analysis by clustering using the aXis2000 program (free for noncommercial use at http://unicorn. mcmaster.ca/aXis2000.html) and PCA_GUI (freeware from http:// www.xray1.physics.sunysb.edu/data/software.php).…”

“…Herein, synchrotron-based studies are carried out to elucidate the role of the interface and defect in the improved PEC ability. In principle, PEC properties depend on the band structure, which is closely related to the atomic and electronic structures of a material. ,, The atomic and electronic structures and the band alignment of materials can be effectively investigated using synchrotron-based X-ray spectroscopic and microscopic techniques, such as X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray emission spectroscopic (XES), VB photoemission (VB-PES), and spatially resolved scanning transmission X-ray microscopic (STXM) techniques. The main advantage of STXM, combined with their corresponding XANES (STXM-XANES), herein is its ability to map the chemical states and to determine spatially resolved electronic structures in the specific region of interest. , These advanced experimental tools are the most suitable for spatially resolving the mechanism that is responsible for the enhancement of PEC properties in BVO/ZnO nanodendrites that are associated with a core–shell heterojunction.…”

Biomimmetic ZrO 2 @ PdO nanocomposites: fabrication, characterization, and water splitting potential exploration

“…Therefore, scientific community and researchers are putting forth significant effort to explore unconventional and renewable energy reservoirs with zero carbon emissions in the environment to reduce the burden on the consumption and depletion of fossil fuel reservoirs 3‐5 . To raise the standard of living in the society, the key roles are to introduce sustainable energy resources and to develop such devices with low carbon emission content to the environment, 46,7 The generation of clean energy is highly required at large as well as at a small scale and has been largely explored by researchers. Nuclear energy, hydroelectric energy, and solar energy are all used on a large scale to create alternative energy reservoirsm, whereas on a smaller scale, novel and promising technologies are being used to construct self‐powered tools 2,5,8 .…”

Solid-state synthesis of CdFe2O4 binary catalyst for potential application in renewable hydrogen fuel generation

“…Equally important to the nature of electrocatalysts for water splitting is the method of catalyst synthesis. Several materials such as chalcogenides 10 , nitrides 11 , sulfides 12 , carbides 13 , phosphides 14 , and oxides 15 have been explored for electrochemical water splitting process. Oxides are the most promising because of their catalytic function and ease of synthesis.…”