Peroxide Yield Research Articles

In Situ Uranium Extraction through the Synthesis of the Uranyl Peroxide Studtite Using a Nonthermal Plasma.

Extraction of uranium from water is an essential step in in situ leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO2)(O2)(H2O)2](H2O)2, by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma. Precipitation of studtite is observed within 5 min of the onset of plasma treatment as confirmed by X-ray diffraction and Raman spectral analysis. The faradaic efficiency of studtite formation is analyzed to estimate the values of hydrogen peroxide yield, 1.23 molecules per incident ion, and the rate constant of the studtite-forming reaction, 4.44 × 107 M-1 s-1. This work is a proof of concept and identifies significant parameters for the future development of a larger scale, higher throughput system.

Degradation of phenol by metal-free electro-fenton using a carbonyl-modified activated carbon cathode: Promoting simultaneous H2O2 generation and activation

The low yield of hydrogen peroxide, narrow pH application range, and secondary pollution due to iron sludge precipitation are the major drawbacks of the electro-Fenton (EF) process. Metal-free electro-Fenton technology based on carbonaceous materials is a promising green pollutant degradation technology. Activated carbon cathodes enriched with carbonyl functional groups were prepared using a two-step annealing method for the degradation of phenol pollutants. The •OH in the activation process of H2O2 were identified using the EPR test technique. The action mechanism of carbonyl groups on H2O2 activation was investigated in conjunction with density functional theory (DFT) calculations. The EPR tests demonstrated that the modified activated carbon could promote the in-situ activation of H2O2 to •OH. And the results of material analysis and DFT showed that C=O could facilitate the activation of hydrogen peroxide through the electron transfer mechanism as an electron-donating group. Electrochemical tests showed that both the oxygen reduction activity and 2e−ORR selectivity of the modified activated carbons were significantly improved. Compared with the original activated carbon cathode and EF, the degradation efficiency of phenol in the ACNH-1000/GF cathode was increased by 58.10% and 45.61%, respectively. Compared with EF, ACNH-1000/GF metal-free electro-Fenton effectively expands the pH application range, and is proven to be less affected by solution initial pH, while avoiding secondary pollution. The metal-free electro-Fenton system can save more than a quarter of the cost of EF system. This study has a deep understanding of the reaction mechanism of the carbonyl modified activated carbon, and provides valuable insights for the design of metal-free catalysts, so as to promote its application in the degradation of organic pollutants.

Metal Supported Metal Oxide Catalysts for Hydrogen Peroxide Production Via Water Splitting

The two-electron water oxidation reaction (WOR) has drawn recent attention as an efficient, simple method of producing on-site hydrogen peroxide through electrochemical water splitting. However, finding electrocatalysts with high activity and stability in the reaction’s harsh oxidizing environment is challenging. This is made especially difficult due to the competing four-electron and one-electron WOR, which necessitate a catalyst material with high selectivity towards the hydrogen peroxide production pathway. Here, we utilize metal/metal oxide coupling interactions to tune metal oxide catalysts to be active for 2 e- WOR via the creation of a Mott-Schottky junction. Metal/metal oxide interactions have been well studied for supported metal catalysts, but their behavior has been less investigated for catalysts where the metal oxide provides the active sites, called inverse catalysts. In this case, the difference in work functions between the metal support and metal oxide semiconductor catalyst drives electron transfer between the two, facilitating electronic interactions which can modulate the binding energy of reaction intermediates at the interface and thus tune the catalytic ability of the metal oxide. In this work, we investigate a variety of metal oxide catalyst and metal support materials and find that a thin layer of indium tin oxide (ITO) supported by a layer of platinum (Pt) has excellent catalytic ability towards 2 e- WOR. The activity, selectivity, and stability of the ITO/Pt catalyst shows significant improvement over the unsupported ITO catalyst and yields hydrogen peroxide production rates greater than those reported in literature using other standard catalysts for this reaction. This method of catalyst engineering also provides a future pathway to create new catalysts for this electrochemical reaction. Figure 1

Hydrogen Peroxide Spillover on Platinum-Iron Hybrid Electrocatalyst for Stable Oxygen Reduction.

Iron-nitrogen-carbon (Fe-N-C) catalysts, although the most active platinum-free option for the cathodic oxygen reduction reaction (ORR), suffer from poor durability due to the Fe leaching and consequent Fenton effect, limiting their practical application in low-temperature fuel cells. This work demonstrates an integrated catalyst of a platinum-iron (PtFe) alloy planted in an Fe-N-C matrix (PtFe/Fe-N-C) to address this challenge. This novel catalyst exhibits both high-efficiency activity and stability, as evidenced by its impressive half-wave potential (E1/2) of 0.93 V versus reversible hydrogen electrode (vs RHE) and minimal 7 mV decay even after 50,000 potential cycles. Remarkably, it exhibits a very low hydrogen peroxide (H2O2) yield (0.07%) at 0.6 V and maintains this performance with negligible change after 10,000 potential cycles. Fuel cells assembled with this cathode PtFe/Fe-N-C catalyst show exceptional durability, with only 8 mV voltage loss at 0.8 A cm-2 after 30,000 cycles and ignorable current degradation at a voltage of 0.6 V over 85 h. Comprehensive in situ experiments and theoretical calculations reveal that oxygen species spillover from Fe-N-C to PtFe alloy not only inhibits H2O2 production but also eliminates harmful oxygenated radicals. This work paves the way for the design of highly efficient and stable ORR catalysts and has significant implications for the development of next-generation fuel cells.

Preparation of electrocatalytic KC-GR/GF membrane cathode and its application in electro-Fenton

ABSTRACT Tetracycline is a common antibiotic that threatens the water environment and requires more stable and efficient ways to degrade it. In this paper, a novel filtered cathode material was prepared by proportionally loading Ketjen Black Carbon (KC) and Graphene (GR) onto Graphite Felt(GF) by coating method, and applied to remove tetracycline from water by electro-Fenton system. The results showed that the highest hydrogen peroxide yield of up to 28.86 mg/L was achieved at the electrodes prepared with a carbon loading of 0.228 g, m (KC):m(polytetrafluoroethylene) = 1:9, and m (KC):m (GR) = 2:2. By characterisation, the contact angle of the loaded graphite felt electrode increased from 71.5° to 126.3°, with faster current responsiveness and larger electrochemically active area than the unloaded electrode. Furthermore, in the application of electro-Fenton: when I = 100 mA, Air = 0.45 L/min, pH = 3 and Fe2+ = 0.3 mol/L, the optimal removal rate of 50 mg/L tetracycline was 99.1%, and the energy consumption was only 8.49 kWh/kg. This electrode has a great advantage in treating the low concentration of tetracycline, and 99.4% of tetracycline can be removed within 30 min. After 8 cycles of tests, the removal rate of tetracycline by this electrode was above 95%. The article demonstrated that the reactor coupled with electrochemical advanced oxidation technology and membrane filtration technology has the effect of enhanced mass transfer, and the Ketjen Black Carbon-Graphene/Graphite Felt (KC-GR/GF) electrocatalytic membrane cathode has the potential and practical significance to be applied for the removal of tetracycline under the electro-Fenton system.

Outstanding photocatalytic degradation performance under low light intensity via mitigating the quenching reaction of oxygen-centered organic radicals and oxygen

Traditional indiscriminate free radicals pose challenges to photocatalyst stability. To address this issue, oxygen-centered organic radicals (OCORs) anchored on catalyst surfaces were developed recently. However, strategies to alleviate the quenching reaction between OCORs and oxygen are lacking. Herein, the tetrasubstituted carbazole derivative-anthraquinone CZAQ-1, generating OCORs, was fabricated as photocatalyst. CzAQ-1 outperforms reported photocatalysts under low-intensity visible light, achieving 100 % degradation efficiency within 90 minutes at 10 mW·cm−2 and 30 minutes at 100 mW·cm−2. It exhibits exceptional stability over 10 cycles and yields hydrogen peroxide production of 3582 μmol·h−1·g−1 during degradation. The outstanding performance is attributed to OCORs serving as the primary oxidative active species, effectively mitigating quenching reactions with oxygen. This process is accomplished through an innovative strategy of reducing the electrostatic potential of oxygen atoms in OCORs. This study provides insights into OCORs and proposes strategies for optimizing organic polymer structures to enhance photocatalytic performance by inhibiting OCORs-oxygen reactions.

Enhanced electrocatalytic removal of bisphenol a by introducing Co/N into precursor formed from phenolic resin waste

Bisphenol A (BPA) is a typical endocrine disruptor, which can be used as an industrial raw material for the synthesis of polycarbonate and epoxy resins, etc. Recently, BPA has appeared on the list of priority new pollutants for control in various countries and regions. In this study, phenolic resin waste was utilized as a multi-carbon precursor for the electrocatalytic cathode and loaded with cobalt/nitrogen (Co/N) on its surface to form qualitative two-dimensional carbon nano-flakes (Co/NC). The onset potentials, half-wave potentials, and limiting current densities of the nitrogen-doped composite carbon material Co/NC in oxygen saturated 0.5 mol H2SO4 were −0.08 V, −0.61 V, and −0.41 mA cm−2; and those of alkaline conditions were −0.65 V, −2.51 V, and −0.38 mA cm−2, and the corresponding indexes were improved compared with those of blank titanium electrodes, which indicated that the constructed nitrogen-doped composite carbon material Co/NC was superior in oxygen reduction ability. The catalysis by metallic cobalt as well as the N-hybridized active sites significantly improved the efficiency of electrocatalytic degradation of BPA. In the electro-Fenton system, the yield of hydrogen peroxide generated by cathodic reduction of oxygen was 4.012 mg L−1, which effectively promoted the activation of hydroxyl radicals. The removal rate of BPA was above 95% within 180 min. This work provides a new insight for the design and development of novel catalyst to degrade organic pollutants.

Interfaces Engineering of Ultrafine Ni@Ni2P/C Core-Shell Heterostructure for High Yield Hydrogen Peroxide Electrosynthesis.

Developing cost-effective and sustainable catalysts with exceptional activity and selectivity is essential for the practical implementation of on-site H2O2 electrosynthesis, yet it remains a formidable challenge. Metal phosphide core-shell heterostructures anchored in carbon nanosheets (denoted as Ni@Ni2P/C NSs) are designed and synthesized via carbonization and phosphidation of the 2D Ni-BDC precursor. This core-shell nanostructure provides more accessible active sites and enhanced durability, while the 2D carbon nanosheet substrate prevents heterostructure aggregation and facilitates mass transfer. Theoretical calculations further reveal that the Ni/Ni2P heterostructure-induced optimization of geometric and electronic structures enables the favored adsorption of OOH* intermediate. All these features endow the Ni@Ni2P/C NSs with remarkable performance in 2e ORR for H2O2 synthesis, achieving a top yield rate of 95.6mgL-1h-1 with both selectivity and Faradaic efficiency exceeding 90% under a wide range of applied potentials. Furthermore, when utilized as the anode of an assembled gas diffusion electrode (GDE) device, the Ni@Ni2P/C NSs achieve in situ H2O2 production with excellent long-term durability (>32h). Evidently, this work provides a unique insight into the origin of 2e ORR and proposes optimization of H2O2 production through nano-interface manipulation.

Chitosan-derived carbon sphere with self-activating behavior for stable oxygen reduction reaction in acid and alkaline media

Utilizing shrimp waste-derived Chitosan as biomass source, we developed metal-free nitrogen and sulfur-doped porous carbon (NSPC) with a high specific surface area of 609.53 m2/g as a remarkable electrocatalyst for oxygen reduction reaction (ORR), surpassing benchmark Pt/C with half-wave (0.8574 V) and onset (0.9573 V) potentials in alkaline (0.1 M KOH) media. Besides high electrocatalytic activity, NSPC-800 showed excellent methanol tolerance ability and significantly low hydrogen peroxide yields (H2O2) of 5 % and 8 % in 0.1 M KOH and 0.5 M H2SO4, which is comparably lower than the previously reported chitosan based non-precious catalysts. Interestingly NSPC-800 displays robust stability in 0.1 M KOH electrolyte, improving the current retention rate from 89.17 % to 95.18 % over an increased operation period, evidencing its self-activating characteristics. This self-activating stability is also mirrored in 0.5 M H2SO4 where both fresh and recycled (after 5000 CV cyles) NSPC-800 catalysts retained more than half of their initial current. Additionally, to identify the nature of the active sites, the ORR measurements were correlated with ex-situ spectroscopy for post-stability of fresh and recycled NSPC-800 catalysts revealed dynamic reconfiguration of nitrogen, sulfur, and oxygen active sites evidenced compared to the pre-stability elemental surface, indicating an adaptive response of the catalyst to the harsh operating environment. In the future, our biomass-derived NSPC-800 will pave the way to develop cost-effective and highly efficient catalysts from waste to energy devices promising a twin-goal approach, contributing to the circular economy and sustainable development goals.

Novel Fe-Ti nanoparticles synthesized in deep eutectic solvents for enhanced photo-electro-Fenton processes: Synergistic effects and environmental applications

An innovative titanium-magnetite (Fe-Ti) catalyst was developed using a production strategy based on water-free solvents such as deep eutectic solvents (DES) for the removal of persistent pollutants. The prepared catalyst was applied in electro-Fenton and photo-electro-Fenton processes. To this end, a new cell design with electrodes based on conductive materials was developed using 3D printing in two different electrochemical cells configurations: vertical electrode configuration (VEC) and horizontal electrode configuration (HEC). The HEC showed good performance attaining a yield hydrogen peroxide production of 20 mg·L−1 and being able to operate in electro-Fenton degradation batch assays for the removal of the drugs (Antipyrine and Lissamine Green B). Then, the heterogeneous bimetallic catalyst (BC-FeTi) was tested and compared with the monometallic Fe catalyst (MC-Fe). The results with both catalysts showed a synergistic effect combining electrochemical oxidation and Fenton reaction, promoting the best removal of the target pollutants. Subsequently, the contribution of UV radiation was evaluated with BC-FeTi, achieving that more than 80 % of both pollutants were removed in 80 min by the photo-Fenton process, confirming the high affinity of oxidizing free radicals for high molecular weight organic molecules. Finally, the simultaneous application of electro- and photo-oxidation (photo-electro-Fenton) significantly improved the removal of the target contaminants from the aqueous solution, achieving complete removal in 50 and 80 min for Lissamine Green B and Antipyrine, respectively. The stability and reusability of BC-FeTi and 3D-printed electrodes were achieved in five successive working cycles, with negligible loss of activity compared to new catalysts, which achieved greater than 99 % removal after five consecutive runs. Leaching of iron and titanium from the catalyst evaluated throughout the cycles, was low, totalling 2.7 and 4.5 % at the end of the fifth cycle.

Unraveling the Tandem Effect of Nitrogen Configuration Promoting Oxygen Reduction Reaction in Alkaline Seawater

AbstractDeveloping seawater‐based high‐performance oxygen reduction reaction (ORR) electrocatalysts is meaningful to renewable energy storage and conversion, and the Fe‐based derivatives encapsulated by nitrogen (N) doped carbon are the typical representative. Nevertheless, unrevealing the mechanism of N configuration to ORR activity and chlorine resistance is still a great challenge. In this work, a feasible strategy is developed to prepare controllable pyridinic/pyrrolic‐N doped carbon‐coated Fe‐based electrocatalysts (FexN‐NC). Drawing support from the H3PO4 blocking based in situ Fourier transform infrared spectroscopy (FTIR) test and density‐functional theory (DFT) calculation, the tandem effect of pyridinic‐N and pyrrolic‐N on ORR is proved. Additionally, the low hydrogen peroxide (H2O2) yield and 4e− pathway of FexN‐NC demonstrate that N doping effectively reduces the adsorption of Cl−, which is consistent with the low Cl− adsorption energy of DFT. The half‐wave potential (E1/2) of FexN‐NC for ORR reaches 0.874 V in alkaline seawater, and ZABs assembled with FexN‐NC as the air cathode deliver a remarkable power density (162 mW cm−2), along with excellent long‐term durability (>400 h).

Nanosecond-Laser-Induced Breakdown of Aqueous Colloidal Solutions of Dysprosium Nanoparticles: The Influence of Nanoparticle Concentration on the Breakdown Plasma and the Intensity of Physical and Chemical Processes

This paper studies the dynamics of the development of laser breakdown plasma in aqueous colloids of dysprosium nanoparticles by analyzing the time patterns of plasma images obtained using a high-speed streak camera. In addition, the distribution of plasma flashes in space and their luminosity were studied, and the amplitude of acoustic signals and the rate of generation of new chemical products were studied depending on the concentration of dysprosium nanoparticles in the colloid. Laser breakdown was initiated by pulsed radiation from a nanosecond Nd:YAG laser. It is shown that the size of the plasma flash, the speed of motion of the plasma–liquid interface, and the lifetime of the plasma flash decrease with an increasing concentration of nanoparticles in the colloid. In this case, the time delay between the beginning of the laser pulse and the moment the plasma flash reaches its maximum intensity increases with increasing concentrations of nanoparticles. Varying the laser fluence in the range from 67 J/cm2 to 134 J/cm2 does not lead to noticeable changes in these parameters, due to the transition of the breakdown plasma to the critical regime. For dysprosium nanoparticles during laser breakdown of colloids, a decrease in the yield of hydrogen peroxide and an increase in the rate of formation of hydroxyl radicals per water molecule, characteristic of nanoparticles of rare earth metals, are observed, which may be due to the participation of nanoparticles and hydrogen peroxide in reactions similar to the Fenton and Haber–Weiss reactions.

Enhancing the nutritional quality of fufu with a starter culture

This study investigates the nutritional enrichment of fufu, a staple African food, by controlling the fermentation of cassava root tuber using a starter culture. Lactic acid bacteria (LAB) were isolated from fermented cassava and analyzed for their technological properties. The physicochemical parameters, proximate and antinutrient content of the fufu samples were determined by standard analytical methods. Twelve LAB were identified as Lactobacilli plantarum (42%), L. acidophilus (25%), L. fermentum (17%), L. brevis (8%), and L. mesenteroides (8%). The LAB isolates produced lactic acid, diacetyl, and hydrogen peroxide ranging from 1.90-2.90, 1.30-2.10, and 1.10 -2.90 mg/mL respectively. Lactobacillus plantarum (FF8) was selected as a starter culture due to its exceptional ability to produce antimicrobial substances, leading to higher yields of lactic acid, diacetyl, and hydrogen peroxide, reducing the fermenting medium's pH. The pH changes in starter-induced fermented fufu (SIFF) and spontaneous fermented fufu (SFF) samples from 0 to 96 hours were 7.10 - 2.60 and 7.10 - 3.30, respectively, while the Total Titratable Acidity (TTA) increased from 0.71-1.79 and 0.28-0.51, respectively. Starter-induced fermented fufu (SIFF) has higher protein, fat, sodium, potassium, iron, zinc, phosphorus, and Vit. C, B1, and A content of 2.93, 0.23 (%) 596.4, 270.9, 8.93, 1.67, 296.67, 5.28, 0.24, and 0.31 (mg/100g) respectively, compared to spontaneous fermented fufu and a significant decrease in antinutrient content, such as cyanide, saponin, and phytates of 0.05, 0.16, and 0.06 (mg/100g), respectively. The study found that L. plantarum FF8 used as a starter culture, improves the nutritional value of fufu and reduces anti-nutrients, suggesting potential health benefits for consumers.

A semi‐empirical approach for determining the number density and void fraction of acoustic cavitation bubbles in sono‐reactors

AbstractA new semi‐empirical technic has been established relying on the linkage between the chemistry in the bulk liquid and that taking place in the acoustic cavitation bubble. The open‐source COPASI software has been used for the optimization of number density according to the total yield of a single bubble and the fitting of the experimental yield of hydrogen peroxide in the sonicated solution. It was observed that the number density is increased with the rise of ultrasound frequency from 200 to 1140 kHz, independently of the saturating gas nature (O2, Ar or air). Within this range of wave frequencies, i.e. from 200 to 1140 kHz, the number of active bubbles goes up from 9.35 × 107 to 3.65 × 1015 L−1 s−1. On the other side, it has been demonstrated that the number density obtained under air atmosphere is greater than that resulting either under argon or oxygen‐saturating gas. Interestingly, with respect to the saturating gas nature (O2, Ar, air) and the range of ultrasound frequency (200–1140 kHz), it was observed that the increase of number density was not necessarily accompanied by a proportional increase of void fraction (total volume of bubbles).

Self-Reinforced Bimetallic Mito-Jammer for Ca2+ Overload-Mediated Cascade Mitochondrial Damage for Cancer Cuproptosis Sensitization.

Overproduction of reactive oxygen species (ROS), metal ion accumulation, and tricarboxylic acid cycle collapse are crucial factors in mitochondria-mediated cell death. However, the highly adaptive nature and damage-repair capabilities of malignant tumors strongly limit the efficacy of treatments based on a single treatment mode. To address this challenge, a self-reinforced bimetallic Mito-Jammer is developed by incorporating doxorubicin (DOX) and calcium peroxide (CaO2) into hyaluronic acid (HA) -modified metal-organic frameworks (MOF). After cellular, Mito-Jammer dissociates into CaO2 and Cu2+ in the tumor microenvironment. The exposed CaO2 further yields hydrogen peroxide (H2O2) and Ca2+ in a weakly acidic environment to strengthen the Cu2+-based Fenton-like reaction. Furthermore, the combination of chemodynamic therapy and Ca2+ overload exacerbates ROS storms and mitochondrial damage, resulting in the downregulation of intracellular adenosine triphosphate (ATP) levels and blocking of Cu-ATPase to sensitize cuproptosis. This multilevel interaction strategy also activates robust immunogenic cell death and suppresses tumor metastasis simultaneously. This study presents a multivariate model for revolutionizing mitochondria damage, relying on the continuous retention of bimetallic ions to boost cuproptosis/immunotherapy in cancer.

Porous Electropolymerized Films of Ruthenium Complex: Photoelectrochemical Properties and Photoelectrocatalytic Synthesis of Hydrogen Peroxide

The photoelectrochemical cells (PECs) performing high-efficiency conversions of solar energy into both electricity and high value-added chemicals are highly desirable but rather challenging. Herein, we demonstrate that a PEC using the oxidatively electropolymerized film of a heteroleptic Ru(II) complex of [Ru(bpy)(L)2](PF6)2 Ru1 {bpy and L stand for 2,2′-bipyridine and 1-phenyl-2-(4-vinylphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline respectively}, polyRu1, as a working electrode performed both efficient in situ synthesis of hydrogen peroxide and photocurrent generation/switching. Specifically, when biased at −0.4 V vs. saturated calomel electrode and illuminated with 100 mW·cm−2 white light, the PEC showed a significant cathodic photocurrent density of 9.64 μA·cm−2. Furthermore, an increase in the concentrations of quinhydrone in the electrolyte solution enabled the photocurrent polarity to switch from cathodic to anodic, and the anodic photocurrent density reached as high as 11.4 μA·cm−2. Interestingly, in this single-compartment PEC, the hydrogen peroxide yield reached 2.63 μmol·cm−2 in the neutral electrolyte solution. This study will serve as a guide for the design of high-efficiency metal-complex-based molecular systems performing photoelectric conversion/switching and photoelectrochemical oxygen reduction to hydrogen peroxide.

Metal-organic framework-derived two-dimensional in-plane Janus catalysts promoting oxygen electroreduction to hydrogen peroxide.

We use MOFs material as precursor to synthesize carbon based two-dimensional (2D) materials loaded with In2 S3 -In2 O3 (In-S-O) nanoparticles. The In-S-O nanoparticles have exhibited Janus architecture composed of two compounds with different crystal structures that are combined in-plane on 2D carbon material surface. The excellent properties of this in-plane Janus material include 2D nanoarchitecture and its Janus properties formed by combining two different crystal structures. It has exhibited excellent electrochemical performances due to its abundant electrochemical active sites and large specific surface area. According to experiments, the electron transfer number of the material for two-electron oxygen reduction is about 2.4, and the hydrogen peroxide yield is 32 mg/h cm2 . In the further test of liquid flow electrolytic cell, the yield can reach up to 172 mg/h cm2 .

Increase of OH radical yields due to the decomposition of hydrogen peroxide by gold nanoparticles under X-ray irradiation.

We elucidate the decomposition mechanism of hydrogen peroxide, which is formed by water radiolysis, by gold nanoparticles (GNPs) under X-ray irradiation. The variations in yields of hydrogen peroxide generated in the presence of GNPs are evaluated using the Ghormley technique. The increase of yields of OH radicals has been quantified using Ampliflu® Red solutions. Almost all hydrogen peroxide generated by irradiation of <25 Gy is decomposed by GNPs, while the yield of OH radicals increases by 1.6 times. The amount of OH radicals thus obtained is almost equivalent to that of the decomposed hydrogen peroxide. The decomposition of hydrogen peroxide is an essential reaction to produce additional OH radicals efficiently in the vicinity of GNPs.

Structure determines performance: isomeric Ti-MOFs for photocatalytic synthesis of hydrogen peroxide.

NH2-UiO-66(Ti) and NH2-MIL-125(Ti) were successfully prepared by using post-synthesis exchange (PSE) and hydrothermal methods, and then these frameworks were tested for photocatalytic hydrogen peroxide production in pure water under visible light. NH2-MIL-125(Ti) exhibits superior activity compared to NH2-UiO-66(Ti) due to its shorter Ti-O bond. In addition, NH2-MIL-125-D (defective) demonstrates a high photocatalytic yield of hydrogen peroxide owing to the presence of defect-rich titanium rich sites.

Iron-Phthalocyanine Based Oxygen Reduction Reaction Electrocatalyst: Structure-Performance Relationship Evolution during Pyrolysis

Fuel cells efficiently convert hydrogen into green electricity however the key bottleneck in their deployment lies at the cathode where oxygen reduction reaction (ORR) exhibits sluggish kinetics and requires high loading of precious metals.In this view, Iron-Nitrogen-Carbons (Fe-Nx-Cs) are promising electrocatalysts to replace expensive and scarce noble metals currently used for the ORR. Fe-Nx-Cs are typically synthesized through pyrolysis using iron, nitrogen and/or carbon precursors of diverse nature. However, in general, pyrolysis is a process poorly understood despite recently a couple of manuscripts with in-situ investigations that have been presented [1-2]. The pyrolysis process defines the structural and chemical evolution of the electrocatalyst that ultimately governs its overall electroactivity. Therefore, in this study, the influence of pyrolysis conditions i.e. temperature (200-1000 °C) and atmosphere (Ar or Ar/H2) on the morphological and superficial development of electrocatalyst was elucidated that initially consisted of Iron (II) Phthalocyanine (FePc) mixed with Ketjen Black 600. The morphological and chemical features were then correlated with the electrochemical performance in alkaline and acidic media through a structure-to-property relationship. In-depth analysis showed that pyrolysis conditions significantly affect the nature and proportion of active Fe-based and nitrogen-based moieties that collaboratively determine the pathway and kinetics of the ORR in acid and alkaline media. X-ray diffraction (XRD) showed that reducing atmosphere (Ar/H2) inhibits the crystallographic growth of Fe-containing nanoparticles. In parallel, the neutral atmosphere (Ar) enhanced the aggregation of Fe into oxides as diffraction peaks corresponded to Fe3O4 after a pyrolysis temperature of 600°C. High-resolution-transmission electron microscopy (HR-TEM) showed the formation of nanoparticles and oxides at temperatures above 600°C. X-ray photoelectron spectroscopy (XPS) revealed multitudinous nitrogen-based moieties with varying proportions in the Fe-Nx-C electrocatalysts developed under different pyrolysis conditions. Interestingly, the samples pyrolyzed in Ar/H2 showed an increasing trend of Fe-Nx with respect to a pyrolysis temperature whereas, in Ar-pyrolysed samples, Fe-Nx started plummeting after 600°C. On the other hand, graphitic nitrogen increased prominently after 700°C in both pyrolytic conditions. Using a rotating ring disc electrode (RRDE), the dependence of performance parameters on the chemical and structural features that evolved during the pyrolysis was clarified. Particularly, in acidic media (0.5 M H2SO4), Fe-Nx-C synthesized at 600 ºC under both Ar and Ar/H2 conditions demonstrated higher electrocatalytic activity, with half-wave potentials (E1/2) of ≈ 0.70-0.72 V (vs RHE) while maintaining the direct tetra-electronic ORR (low peroxide production). A similar trend was witnessed in an alkaline media (0.1 M KOH) but with relatively higher performance than in acid media. The highest onset potentials and E1/2 observed in alkaline media were obtained by the Fe-Nx-Cs pyrolyzed at 600°C and 700 ºC in both atmospheres i.e. Ar (E1/2 ≈ 0. 89 V vs RHE) and Ar/H2 (E1/2 ≈ 0. 87 V vs RHE). A prompt reduction in the performance was highlighted at higher pyrolysis temperatures where an increase in peroxide yield might be related to the formation of iron oxide nanoparticles. This work presents a novel insight into the evolution of Fe-Nx-C electrocatalysts during pyrolysis with optimum performance.