Metal Borides as Excellent Co-Catalysts for Boosted and Long-Lasting Fenton-like Reaction: Dual Co-Catalytic Centers of Metal and Boron

Dual-strategy engineered nickel phosphide for achieving efficient hydrazine-assisted hydrogen production in seawater

Electrocatalytic hydrogen production in seawater to alleviate freshwater shortage pressures is promising, but is hindered by the sluggish oxygen evolution reaction and detrimental chloride electrochemistry. Herein, a dual strategy approach of Fe-doping and CeO2-decoration in nickel phosphide (Fe-Ni2P/CeO2) is rationally designed to achieve superior bifunctional catalytic performance for the hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) in seawater. Notably, the two-electrode Fe-Ni2P/CeO2-based hybrid seawater electrolyzer realizes energy-efficient and chlorine-free hydrogen production with ultralow cell voltages of 0.051 and 0.597 V at 10 and 400 mA cm-2, which are significantly lower than those needed in the hydrazine-free seawater electrolyzer. Density functional theory calculations manifest that the combination of Fe doping and heterointerface construction between Fe-Ni2P and CeO2 can adjust the electronic structure of the Ni2P and optimize the water dissociation barrier and hydrogen adsorption free energy, leading to improvement of the intrinsic catalytic performance. This route affords a feasible solution for future large-scale hydrogen generation using abundant ocean water.

FePO4/WB as an efficient heterogeneous Fenton-like catalyst for rapid removal of neonicotinoid insecticides: ROS quantification, mechanistic insights and degradation pathways

Iron-based catalysts for peroxymonosulfate (PMS) activation hold considerable potential in water treatment. However, the slow conversion of Fe(III) to Fe(II) restricts its large-scale application. Herein, an iron phosphate tungsten boride composite (FePO4/WB) was synthesized by a simple hydrothermal method to facilitate the Fe(III)/Fe(II) redox cycle and realize the efficient degradation of neonicotinoid insecticides (NEOs). Based on electron paramagnetic resonance (EPR) characterization, scavenging experiments, chemical probe approaches, and quantitative tests, both radicals (HO• and SO4⋅-) and non-radicals (1O2 and Fe(IV)) were produced in the FePO4/WB-PMS system, with relative contributions of 3.02 %, 3.58 %, 6.24 %, and 87.16 % to the degradation of imidacloprid (IMI), respectively. Mechanistic studies revealed that tungsten boride (WB) promoted the reduction of FePO4, and the generated Fe(II) dominantly activated PMS through a two-electron transfer to form Fe(IV), while a minority of Fe(II) engaged in a one-electron transfer with PMS to produce SO4⋅-, HO•, and 1O2. In addition, four degradation pathways of NEOs were proposed by analyzing the byproducts using UPLC-Q-TOF-MS/MS. Besides, seed germination experiments revealed the biotoxicity of NEOs was significantly reduced after degradation via the FePO4/WB-PMS system. Meanwhile, the recycling experiments and continuous flow reactor experiments showed that FePO4/WB exhibited high stability. Overall, this study provided a new perspective on water remediation by Fenton-like reaction. ENVIRONMENTAL IMPLICATION: Neonicotinoids (NEOs) are a type of insecticide used widely around the world. They've been found in many aquatic environments, raising concerns about their possible negative effects on the environment and health. Iron-based catalysts for peroxymonosulfate (PMS) activation hold great promise for water purification. However, the slow conversion of Fe(III) to Fe(II) restricts its large-scale application. Herein, iron phosphate tungsten boride composite (FePO4/WB) was synthesized by a simple hydrothermal method to facilitate the Fe(III)/Fe(II) redox cycle and realize the efficient degradation of NEOs. The excellent stability and reusability provided a great prospect for water remediation.

Were Persulfate-Based Advanced Oxidation Processes Really Understood? Basic Concepts, Cognitive Biases, and Experimental Details

Persulfate (PS)-based advanced oxidation processes (AOPs) for pollutant removal have attracted extensive interest, but some controversies about the identification of reactive species were usually observed. This critical review aims to comprehensively introduce basic concepts and rectify cognitive biases and appeals to pay more attention to experimental details in PS-AOPs, so as to accurately explore reaction mechanisms. The review scientifically summarizes the character, generation, and identification of different reactive species. It then highlights the complexities about the analysis of electron paramagnetic resonance, the uncertainties about the use of probes and scavengers, and the necessities about the determination of scavenger concentration. The importance of the choice of buffer solution, operating mode, terminator, and filter membrane is also emphasized. Finally, we discuss current challenges and future perspectives to alleviate the misinterpretations toward reactive species and reaction mechanisms in PS-AOPs.

New Insights into Photo-Fenton Chemistry: The Overlooked Role of Excited IronIII Species

Direct photoreduction of FeIII is a widely recognized route for accelerating FeIII/FeII cycle in photo-Fenton chemistry. However, most of the wavelengths covering the full spectral range are insufficient to supply enough photon energy for the direct reduction process. Herein, the hitherto neglected mechanism of FeIII reduction that the FeIII indirect reduction pathway initiated by light energy-dependent reactivity variation and reactive excited state (ES) was explored. Evolution of excited-state FeIII species (*FeIII) resulting from metal-centered charge excitation (MCCE) of FeIII is experimentally verified using pulsed laser femtosecond transient absorption spectroscopy with UV-vis detection and theoretically verified by quantum chemical calculation. Intense photoinduced intravalence charge transition was observed at λ = 380 and 466 nm, revealing quartet 4MCCE and doublet 2MCCE and their exponential processes. Light energy-dependent variation of *FeIII reactivity was kinetically certified by fitting the apparent rate constant of the radical-chain sequence of photo-Fenton reactions. Covalency is found to compensate for the intravalence charge separation following photoexcitation of the metal center in the MCCE state of Fenton photosensitizer. The *FeIII is established as a model, demonstrating the intravalence hole delocalization in the ES can be leveraged for photo-Fenton reaction or other photocatalytic schemes based on electron transfer chemistry.

Rational design of nanozyme with integrated sample pretreatment for colorimetric biosensing

Nanozymes have been widely used in the field of biosensing owing to their high stability, low cost, adjustable catalytic activity, and convenient modification. However, achieving high selectivity and sensitivity simultaneously in nanozyme-based colorimetric sensing remains a major challenge. Nanozymes are nanomaterials with enzyme-simulating activity that are often used as solid-phase adsorbents for sample pretreatment. Our design strategy integrated sample pretreatment function into the nanozyme through separation and enrichment, thereby improving the selectivity and sensitivity of nanozyme-based colorimetric biosensing. As a proof-of-concept, glucose was used as the model analyte in this study. A phenylboric acid-modified magnetic nanozyme (Cu/Fe3O4@BA) was rationally designed and synthesized. Selectivity was enhanced by boronate-affinity specific adsorption and the elimination of interference after magnetic separation. In addition, magnetic solid-phase extraction enrichment was used to improve the sensitivity. A recovery rate of more than 80% was reached when the enrichment factor was 50. The synthesized magnetic Cu/Fe3O4@BA was recyclable at least five times. The proposed method exhibited excellent selectivity and sensitivity, simple operation, and recyclability, providing a novel and practical strategy for designing multifunctional nanozymes for biosensing.

Synthesis of iron-boride/carbon-nitride composites and their applications in chemodynamic therapy

Chemodynamic therapy (CDT) is an emerging treatment strategy that inhibits tumor growth by catalyzing the generation of reactive oxygen species (ROS), such as hydroxyl radicals (•OH), using specific nanomaterials. Herein, we have developed a new class of iron-based nanomaterials, i.e., iron-based borides (FeB), using the superchaotropic effect of a boron cluster (closo-[B12H12]2-) and organic ligands, followed by high-temperature calcination. Experimental data and theoretical calculations revealed that FeB nanoparticles exhibit a Fenton-like effect, efficiently decomposing hydrogen peroxide into •OH and thus increasing the concentration of ROS. FeB nanomaterials demonstrate excellent catalytic performance, efficiently generate ROS, and exert significant antitumor effects in cell experiments and animal models. Therefore, FeB nanomaterials have considerable potential for application in tumor treatment and offer new insights for the development of novel and efficient cancer therapy strategies.

Enhanced Fe(ii)/Fe(iii) cycle by boron enabled efficient Cr(vi) removal with microscale zero-valent iron

Recently, researchers have been paying much attention to zero-valent iron (ZVI) in the field of pollution remediation. However, the depressed electron transport from the iron reservoir to the iron oxide shell limited the wide application of ZVI. This study was aimed at promoting the performance of microscale ZVI (mZVI) for hexavalent chromium (Cr(vi)) removal by accelerating iron cycle with the addition of boron powder. It was found that the addition of boron powder enhanced the Cr(vi) removal rate by 2.1 times, and the proportion of Cr(iii) generation after Cr(vi) removal process also increased, suggesting that boron could promote the reduction pathway of Cr(vi) to Cr(iii). By further comparing the Cr(vi) removal percentage of Fe(iii) with or without the boron powder, we found that boron powder could promote the percentage removal of Cr(vi) with Fe(iii) from 10.1% to 33.6%. Moreover, the presence of boron powder could decrease the potential gap values (ΔEp) between Fe(iii) reduction and Fe(ii) oxidation from 0.668 V to 0.556 V, further indicating that the added boron powder could act as an electron sacrificial agent to promote the reduction process of Fe(iii) to Fe(ii), and thus enhancing the reduction of Cr(vi) with Fe(ii). This study shed light on the promoted mechanism of Cr(vi) removal with boron powder and provided an environmentally friendly and efficient approach to enhance the reactivity of the mZVI powder, which would benefit the wide application of mZVI technology in the environmental remediation field.