PEC water splitting using mats of calcined TiO2 rutile nanorods photosensitized by a thin layer of Ni-benzene dicarboxylic acid MOF

Two-Dimensional Sb Modified TiO2 Nanorod Arrays as Photoanodes for Efficient Solar Water Splitting

As one of the widely studied semiconductor materials, titanium dioxide (TiO₂) exhibits high photoelectrochemical (PEC) water-splitting performance as well as high chemical and photo stability. However, limited by a wide band gap and fast electron-hole recombination rate, the low solar-to-hydrogen conversion efficiency remains a bottleneck for the practical application of TiO₂-based photoelectrodes. To improve the charge separation and water oxidation efficiency of TiO₂ photoanodes, antimonene, a two-dimensional (2D) material obtained by liquid-phase exfoliation, was assembled onto TiO₂ nanorod arrays (TNRAs) by a simple drop-coating assembly process. PEC measurements showed that the resulting 2D Sb/TiO₂ photoelectrode displayed an enhanced photocurrent density of about 1.32 mA cm^-2 in 1.0 M KOH at 0.3 V vs. Hg/HgO, which is ~1.65 times higher than that of the pristine TNRAs. Through UV-Vis absorption and electrochemical impedance spectroscopy measurements, it was possible to ascribe the enhanced PEC performances of the 2D Sb/TiO₂ photoanode to increased absorption intensity in the visible light region, and improved interfacial charge-transfer kinetics in the 2D Sb/TiO₂ heterojunction, which promotes electron-hole separation, transfer, and collection.

Plasmon-induced hole-depletion layer on p-n heterojunction for highly efficient photoelectrochemical water splitting

The photoelectrocatalytic (PEC) water splitting efficiency of semiconductor photoelectrodes is mainly limited by the effective separation and transfer of photogenerated charges. Zinc indium sulfide-cuprous oxide (ZnIn₂S₄-Cu₂O) p-n heterojunction is constructed to enhance the PEC properties of ZnIn₂S₄. The nickel hydroxide iron oxide (NiFeOOH) layer on the surface of the heterojunction can be used as a hole depletion layer under the induction of plasmon resonance of the most surface silver (Ag) (the holes transferred from Cu₂O valence band to NiFeOOH layer can be excited by Ag to produce hot electron consumption, which makes the last remaining hot holes participate in the water oxidation reaction) to further promote the carrier separation and transfer. The results exhibit that ZnIn₂S₄/Cu₂O/NiFeOOH/Ag photoelectrode with dramatically enhanced photocurrent density of 1.22 mA/cm² at 1.23 V versus the reversible hydrogen electrode (V_RHE), which is 9.4 times higher than the pure ZnIn₂S₄. This work provides a promising concept to design photoelectrodes efficiently in PEC water splitting.

Operando Photo-Electrochemical Catalysts Synchrotron Studies

The attempts to develop efficient methods of solar energy conversion into chemical fuel are ongoing amid climate changes associated with global warming. Photo-electrocatalytic (PEC) water splitting and CO₂ reduction reactions show high potential to tackle this challenge. However, the development of economically feasible solutions of PEC solar energy conversion requires novel efficient and stable earth-abundant nanostructured materials. The latter are hardly available without detailed understanding of the local atomic and electronic structure dynamics and mechanisms of the processes occurring during chemical reactions on the catalyst–electrolyte interface. This review considers recent efforts to study photo-electrocatalytic reactions using in situ and operando synchrotron spectroscopies. Particular attention is paid to the operando reaction mechanisms, which were established using X-ray Absorption (XAS) and X-ray Photoelectron (XPS) Spectroscopies. Operando cells that are needed to perform such experiments on synchrotron are covered. Classical and modern theoretical approaches to extract structural information from X-ray Absorption Near-Edge Structure (XANES) spectra are discussed.

A Review of Electrical Assisted Photocatalytic Technologies for the Treatment of Multi-Phase Pollutants

This article reviews the fundamental theories and reaction mechanisms of photocatalytic technologies with the assistance of electrical field for degrading multi-phase pollutants. Photo(electro)catalysis including photocatalytic oxidation (PCO) and photoelectrocatalytic oxidation (PECO) have been a potential technologies applied for the treatment of organic and inorganic compounds in the wastewaters and waste gases, which has been treated as a promising technique by using semiconductors as photo(electro)catalysts to convert light or electrical energy to chemical energy. Combining photocatalytic processes with electrical field is an option to effectively decompose organic and inorganic pollutants. Although photocatalytic oxidation techniques have been used to decompose multi-phase pollutants, developing efficient advanced oxidation technologies (AOTs) by combining photocatalysis with electrical potential is urgently demanded in the future. This article reviews the most recent progress and the advances in the field of photocatalytic technologies combined with external electrical field, including the characterization of nano-sized photo(electro)catalysts, the degradation of multi-phase pollutants, and the development of electrical assisted photocatalytic technologies for the potential application on the treatment of organic and inorganic compounds in the wastewaters and waste gases. Innovative oxidation techniques regarding photo(electro)catalytic reactions with and without oxidants are included in this review article.

The Surge of Metal-Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment.