Rapid Synthesis of Ultrathin Ni:FeOOH with In Situ-Induced Oxygen Vacancies for Enhanced Water Oxidation Activity and Stability of BiVO₄ Photoanodes

Abstract

The coupling of oxygen evolution reaction (OER) catalysts with photoanodes is a promising strategy for enhancing the photoelectrochemical (PEC) performance by passivating photoanode's surface defect states and facilitating charge transfer at the photoanode/electrolyte interface. However, a serious interface recombination issue caused by poor interface and OER catalysts coating quality often limits further performance improvement of photoanodes. Herein, a rapid Fenton-like reaction method is demonstrated to produce ultrathin amorphous Ni:FeOOH catalysts with in situ-induced oxygen vacancies (Vo) to improve the water oxidation activity and stability of BiVO 4 photoanodes. The combined physical characterizations, PEC studies, and density functional theory calculations revealed that the reductive environment in a Fenton-like reaction in situ produces abundant Vo in Ni:FeOOH catalysts, which significantly improves charge separation and charge transfer efficiency of BiVO 4 while also offering abundant active sites and a reduced energy barrier for OER. As a result, Ni:FeOOH-Vo catalysts yielded a more than 2-fold increased photocurrent density in the BiVO 4 photoanode (from 1.54 to 4.15 mA cm −2 at 1.23 V RHE ), accompanied by high stability for 5 h. This work not only highlights the significance of abundant Vo in catalysts but also provides new insights into the rational design and fabrication of efficient and stable solar water-splitting systems.

CoFe Layered Double Hydroxide Supported on Fe-Doped BiVO4 Nanoparticles as Photoanode for Photoelectrochemical Water Splitting

“…Remarkably, the CoFe/Fe-BiVO 4 sample possesses a substantial oxygen vacancy content of 60.56%, which is approximately 3.2 times higher than that of pristine BiVO 4 (18.59%). It is clear that the largest increase in the oxygen vacancy content of the CoFe-LDH-modified sample is due to the fact that the photodeposition of amorphous CoFe hydroxide produces a large amount of oxygen vacancies to balance the large amount of low valent metal ions such as Co 2+ , Fe 2+ , and other low valent metal ions. , Here, the generation of oxygen vacancies could be intricately linked to the formation of small polarons, exerting significant influence on both the electronic and atomic . Initially, the samples were first electrodeposited and then oven-dried.…”

Bismuth Vanadate and 3D Graphene Composite Photoanodes for Enhanced Photoelectrochemical Oxidation of Water

“…The relaxation time measured using the time-resolved spectroscopic measurements considers the time for its de-excitation process, whereas the hole takes some more time for its complete relaxation/interfacial process. EIS measurements are capable of proving the categorized information about the relaxation processes inside the solid electrode and at the interface; presently, the EIS data have been fitted with a simple Randle circuit, where the resulting relaxation time includes all the process involved at the photoelectrode. ,− The diffusion length measured from the spectroscopic technique varies in a few nanometer range, whereas the diffusion length values reported from the Bode plots fall over 100 μm. The lifetime measurements from the time-resolved spectroscopic technique consider the lifetime of the holes at the excited state, which are related to the electronic structure and electronic conductivity.…”

Surface Oxygen Species in Metal Oxide Photoanodes for Solar Energy Conversion

“…This positive shift in surface atoms indicates a less stable final state compared to bulk excitation. By comparing the peak area ratios corresponding to oxygen vacancies and lattice oxygen in the oxygen characteristic peaks of different materials, the relative number of oxygen vacancies can be obtained [ 106 ], for example, in a study by Kong et al for WO 3 with a different spatial distribution of oxygen vacancies through laser treatment [ 38 ]. By analyzing the photoelectron emission signal of surface oxygen species, the lattice oxygen, oxygen vacancy, and adsorbed hydroxyl group on the surface of the material can be relatively quantified ( Figure 10 a).…”