Peroxide Evolution Research Articles

Composition-Regulated Photocatalytic Activity of ZnIn2S4@CdS Hybrids for Efficient Dye Degradation and H2O2 Evolution.

Heterostructures of visible light-absorbing semiconductors were prepared through the growth of ZnIn2S4 crystallites in the presence of CdS nanostructures. A variety of hybrid compositions was synthesized. Both reference samples and heterostructured materials were characterized in detail, regarding their morphology, crystalline character, chemical speciation, as well as vibrational properties. The abovementioned physicochemical characterization suggested the absence of doping phenomena, such as the integration of either zinc or indium ions into the CdS lattice. At specific compositions, the growth of the amorphous ZnIn2S4 component was observed through both XRD and Raman analysis. The development of heterojunctions was found to be composition-dependent, as indicated by the simultaneous recording of the Raman profiles of both semiconductors. The optical band gaps of the hybrids range at values between the corresponding band gaps of reference semiconductors. The photocatalytic activity was assessed in both organic dye degradation and hydrogen peroxide evolution. It was observed that the hybrids demonstrating efficient photocatalytic activity in dye degradation were rather poor photocatalysts for hydrogen peroxide evolution. Specifically, the hybrids enriched in the CdS component were shown to act efficiently for hydrogen peroxide evolution, whereas ZnIn2S4-enriched hybrids demonstrated high potential to photodegrade an azo-type organic dye. Furthermore, scavenging experiments suggested the involvement of singlet oxygen in the mechanistic path for dye degradation.

Poly (heptazine imide) nanocrystal for hydrogen peroxide evolution in the dark by accumulating photo-generated electrons

Poly (heptazine imide) nanocrystal for hydrogen peroxide evolution in the dark by accumulating photo-generated electrons

Boosting photocatalytic hydrogen peroxide evolution through aerobic oxidative dehydrogenation of benzyl alcohol over amino acid hyper-cross-linked polymer in two-phase system

The fusion of photocatalytic hydrogen peroxide (H2O2) production with the generation of high-value organic compounds carries the potential to optimize the utilization of solar energy. The efficient generation and separation of products constitute indispensable elements in constructing a proficient reaction system. Herein, the photocatalytic production of H2O2 via the aerobic oxidative dehydrogenation of benzyl alcohol (BA) was realized through the application of an amino acid hyper-cross-linked polymer (H6P-HCPs) in two-phase system. The outcomes unveiled that the H6P-HCPs with 1:6 M ratio of L-phenylalanine (L-Phe) and hexaphenylbenzene (HPB) achieves the highest generation rate of H2O2 (29.26 mmol∙gcat-1∙h-1), stoichiometric amount of benzyl alcohol oxidation products were obtained as 96% benzaldehyde (23.94 mmol∙gcat-1∙h-1) and 4% benzoic acid (5.56 mmol∙gcat-1∙h-1). Time-dependent density functional theory (TDDFT) calculations illuminated that the presence of L-Phe monomers of H6P-HCPs not only facilitated electron transfer from L-Phe to HPB, capitalizing on electronegativity differentials, but also instigated the formation of O2•- while concurrently adjusting its hydrophobic nature. These factors, in concert, were instrumental in the accomplishment of this highly efficient photocatalytic process.

3D printed carbon black-polylactic acid/copper (CB-PLA/Cu) sensor for improved sustainability in monitoring photocatalytic hydrogen peroxide evolution

As the photocatalytic generation of hydrogen peroxide continues to gather increasing interest, there is a significant need to introduce more sustainable methods to monitor the reaction process. The fabrication of low-cost sustainable electrochemical sensors offers an enticing alternative to the current standard methods. This study reports the first use of an electrochemical sensor to monitor such a process. A highly reproducible 3D printed carbon black-polylactic acid/copper sensor with an extremely low fabrication cost of €0.012 was employed to accurately monitor the photocatalytic evolution of hydrogen peroxide. The accuracy was confirmed through strong correlation with a standard fluorescence spectroscopic method. The sensor displayed limit of detection and limit of quantification values of 0.24 µM and 0.79 µM respectively, and a sensitivity of 217 µA mM−1 cm-2, while also showing strong selectivity towards hydrogen peroxide in the presence of potential interfering species. Moreover, the electrocatalytic surface was capable of ≥ 3x regeneration without significant loss in activity bringing a ≥ 75 % decrease in analysis cost and a significant reduction in potential waste material. This novel approach to monitoring the photocatalytic evolution of hydrogen peroxide presents as a more economical and sustainable alternative to current methods.

Electronic Tuning of SnO2 by rGO Nanosheets for Highly Efficient Photocatalytic Hydrogen Peroxide Evolution

Electronic Tuning of SnO₂ by rGO Nanosheets for Highly Efficient Photocatalytic Hydrogen Peroxide Evolution

Heterostructured PHI‐PTI/Li+Cl− Carbon Nitrides for Multiple Photocatalytic Applications

Two series of novel carbon nitride photocatalysts, Rho‐CN (“rhodizonate‐doped carbon nitride”) and Rho‐CN‐TC (Rho‐CN treated in potassium thiocyanate melt), are synthesized in a multistep fashion via copolymerization of cyanamide with potassium rhodizonate. The formed ionic carbon nitrides are composed of poly(triazine imide) (PTI/Li+Cl−) and potassium poly(heptazine imide) (K‐PHI) phases and provide a broad absorption range up to 800 nm. The photocatalysts are characterized by several techniques (including diffuse reflectance ultraviolet–visible, powder X‐ray diffraction, Fourier transform infrared, scanning electron microscopy, and electrochemical methods) and studied in a series of photocatalytic reactions, including red light‐promoted benzylamine oxidation, dual photoredox/nickel C–N cross‐coupling, and hydrogen peroxide evolution. The optimal ratio of rhodizonate dopant in its mixture with cyanamide is found to be 0.5 mol%. The performance of the newly synthesized materials is comparable to the activities of the benchmark catalysts K‐PHI and CN‐OA‐m (defective poly(heptazine imide) doped with oxamide), while not requiring more expensive nitrogen sources for preparation, like 5‐aminotetrazole, or multiple oven cycles.

Water flow induced piezoelectric polarization and sulfur vacancy boosting photocatalytic hydrogen peroxide evolution of cadmium sulfide nanorods

Piezo-photocatalytic H2O2 production utilizing earth-abundant solar and mechanical energies, oxygen and water is a highly appealing route to produce renewable energy carriers. However, piezoelectric polarization always suffers from high-frequency mechanical vibration, which severely restricts its actual applications. Here, we report prominent piezo-photocatalytic H2O2 evolution from pure water triggered by low-frequency water flow induced mechanical stress over 1D CdS nanorods with sulfur vacancy (CdS NRs). The polar CdS NRs possess benign piezoelectric property and favorable morphology, enabling high sensitivity and respond to weak force of water flow, which contribute to yielding large piezoelectric polarization for photogenerated charges separation. Piezoelectric polarization also shows an inhibition effect on the photocorrosion of CdS to ·SO3-. Besides, DFT calculations demonstrate that sulfur vacancy allows enhanced O2 adsorption and formation of the intermediate *OOH on the surface of CdS. Under simultaneous visible light and high-speed stirring, CdS NRs display a remarkably synergetic piezo-photocatalytic H2O2 production (1631.4 µmol g−1 h−1) without any sacrificial agents, 2.4 and 73.8 times of that under sole visible light and mechanical agitation, respectively. Importantly, it achieves an apparent quantum efficiency (AQY) of 1.32% at wavelength up to 500 nm and a solar-to-chemical (STC) conversion efficiency of 0.05% under one-sun illumination, which far exceeds other reported sulfide-based catalysts. This work integrates well with polarization engineering, defect engineering and morphology engineering to enhance catalytic behavior, providing a feasible strategy for designing efficient piezo-photocatalysts sensitive to weak mechanical forces.

Cooperation of congenital and acquisitus sulfur vacancy for excellent photocatalytic hydrogen peroxide evolution of CdS nanorods from air

Photocatalysis over semiconductors for producing hydrogen peroxide (H2O2) due to its renewable and sufficient sunlight as driving force has attracted more attention. However, the H2O2 evolution performance that is severely dependent on surface structure of photocatalysts is still inferior. Here we design sulfur vacancies (Sv)-rich CdS nanorods (CdS NRs), and disclose that the congenital Sv and acquisitus Sv in-situ created in the reaction process co-contribute to the efficient photocatalytic H2O2 production. The CdS NRs with abundant congenital Sv exhibit higher carrier separation efficiency and remarkably stronger O2 adsorption ability. Importantly, we discover that the Sv concentration in all the CdS serial samples increases after the H2O2 evolution reaction compared with that before photocatalytic reaction, and the increase level of acquisitus Sv concentration inversely correlates with congenital Sv concentration. Theoretical calculations confirm that the O2 adsorption energy on the surface of CdS NRs with Sv (−0.723 eV) is much lower than that of defect-free CdS (1.293 eV). Optimized by the two types of Sv, CdS NRs-24 h delivers a superior photocatalytic H2O2 production rate of 2974.7 μmol g1h−1 under visible light, far exceeding the previously reported sulfide photocatalysts. This work is anticipated to offer new perspectives into designing and understanding of sulfides for photocatalytic H2O2 evolution.

(Invited) Crystal Engineering of Bismuth Vanadate for Enhanced Light-Driven Water Oxidation

Photocatalytic and photoelectrochemical processes employing photoactive semiconductors are two key systems in harvesting sunlight for energy and environmental applications. Strategies have been formulated to improve the properties of the semiconductor for better performances. However, requirements to yield excellent performances are different in these two distinctive systems. Understanding of the underlying mechanism for the photoexcited charge transportation in relation to their photoactivities is of fundamental importance for rational design of high-performing photoactive materials, which may serve as a useful guideline for the fabrication of good photocatalysts or photoelectrodes toward sustainable solar fuels generation. Many photoactive semiconductors, including bismuth vanadate, are having inadequate charge transport properties such as low charge mobility, short lifetime, and slow surface kinetics. Standalone single photoactive semiconductors also faces the challenge of meeting the needs for large redox potentials with a sufficiently narrow bandgap for visible light absorption. Coupling two or more components into a photoactive composite may address some of these drawbacks by utilizing the strengths of the individual semiconductors. In this presentation, the charge transportation behavior of single component photoactive semiconductor based on bismuth vanadate, and the composite materials forming heterojunction with bismuth vanadate, will be examined and discussed (example of modulation of BiVO4 photocatalyst in Figure 1 ).1 Typically, crystal facet engineering, interfacing with non-photoactive secondary component, and narrowing the crystal size into quantum-confinement region, will be the three strategies to be shared with audience during the presentation. Preferential charge migration depending on the crystal facet has been reported in various photocatalysts. These promoted charge migration can be further boosted with spatially deposited cocatalysts on the selective redox sites. The manipulation of crystal facet allows the controlled electron transfer to induce 4-electron process (oxygen evolution) or 2-electron process (hydrogen peroxide evolution) in water oxidation. Nanosizing the bismuth vanadate into <10 nm region with distinctive yet interconnected crystal domains leads to the expansion of band structure. Conduction band of bismuth vanadate was expanded to energetic level capable of reducing proton into H2. The traditional O2-evolving bismuth vanadate is now demonstrating H2-producing properties. Figure 1: Time-resolved microwave conductivity (TRMC) spectroscopy signals measured for BiVO4 and its Power-law decay fittings.Reference1. H. Wu, R. Irani, K. Zhang, L. Jing, H. Dai, H. Y. Chung, F. F. Abdi, Y. H. Ng*, Unveiling Carrier Dynamics in Periodic Porous BiVO4 Photocatalyst for Enhanced Solar Water Splitting. ACS Energy Lett. 2021, 6, 3400-3407. Figure 1

Rational modification of hydroxy-functionalized covalent organic frameworks for enhanced photocatalytic hydrogen peroxide evolution

Covalent organic frameworks (COFs), a class of flexibly tunable crystalline materials, have fascinating potential in photocatalytic hydrogen peroxide (H2O2) evolution under visible light irradiation. However, achieving efficient catalytic activity by tuning the composition of COFs and the linkages of building blocks is still a challenge. Herein, four imine-linked COFs with different numbers of hydroxy-functionalized are constructed to unveil the latent structure–activity relationship between the reversibility of bonding in supramolecular chemistry and the photocatalytic H2O2 performance. As the optimized material, TAPT-HTA-COF (1H-COF) containing single hydroxy group in aldehyde node exhibits a highest ordered structure and conjugation degree along and across the plane in the extended frameworks originating from the flexibly reversible iminol-to-ketoenamine tautomerism than others, which broadens the visible light absorption and accelerates the dissociation of photogenerated carriers in 1H-COF. These merits ensure that 1H-COF has the highest H2O2 yield (44.5 μmol L−1) and O2 two-electron reduction pathway among the four COFs under visible light irradiation (λ > 420 nm, 10 vol% isopropanol aqueous solution). At the same time, the long-range ordered framework of 1H-COF is well preserved during the photocatalytic H2O2 evolution process assisted by the proton-induced tautomerization. This work facilitates the design and development of COF-based photocatalysts in the evolution of H2O2.

Photocatalytic Evolution of Hydrogen Peroxide: A Minireview

Hydrogen peroxide (H2O2) has demonstrated applicability in a wide range of applications, spanning from a bleaching agent in the pulp industry, environmental remediation, and fuel cell technology. Industrial scale synthesis, either by the anthraquinone method or catalytic oxidation of hydrogen gas, has serious drawbacks which are related with energy demanding and multi-step processes. An alternative green strategy involves the photocatalytic synthesis of H2O2. All that is needed is the renewable energy of the sun, a semiconducting species absorbing in the visible region, water, and oxygen. In this minireview, we describe the evolution of research milestones that have been achieved within the recent decades regarding the development of functional photocatalytic systems. In the early studies, back in the 1980’s, TiO2-based systems were mostly investigated. However, due to the large band gap of titania (3.2 eV), alternative semiconductors were studied which strongly absorb in the visible region. Thus, a variety of semiconductor families have been investigated, such as doped titania systems, other metal oxides, metal sulfides, organic semiconductors, metal-organic frameworks, carbon nitride systems, etc. In parallel, the development of functional dopants onto the surface of the main semiconductor has lead to both the inhibition of electron-hole recombination and H2O2 degradation. The current minireview collectively provides the studies of the higher H2O2 production rates and offer some suggestions for the near future.

The effect of precursor selection on the microwave-assisted synthesis of graphitic carbon nitride

Currently, there is a strong demand to identify the most sustainable methods for the production of nanostructured materials. In particular, for carbon nitride photocatalysts, with numerous attractive qualities, it is essential to assess the impact of different precursors on the microwave synthesis of these materials and understand the respective influence on the resulting photocatalytic performances. In the present work, the synthesis procedure comprises two microwave steps and six distinct precursors (dicyandiamide, melamine, guanidine carbonate, guanidine hydrochloride, thiourea, or urea) to obtain materials with varying exfoliated nanosheets-like disordered structures, among other morphological, structural and optical properties. The different characteristics of the photocatalysts produced are described, and correlations are established between these properties and the respective photocatalytic results for phenol degradation and selective hydrogen peroxide evolution with phenol or isopropanol. The best performing photocatalyst for phenol (kapp = 0.065 min−1) and total organic carbon removal (71.0%) was that prepared with the urea precursor and after a two-step microwave treatment, ascribed to the higher surface area, increased pore volume and hypsochromic photoluminescence emission. The larger rates of H2O2 were achieved in specific experiments with isopropanol (15026 µmol gcat−1 h−1) and using a guanidine hydrochloride as the photocatalyst precursor. Expectantly, these results will contribute to developing more effective and sustainable synthesis methods of graphitic carbon nitride materials.

Piezocatalytic and Photocatalytic Hydrogen Peroxide Evolution of Sulfide Solid Solution Nano-Branches from Pure Water and Air.

Hydrogen peroxide (H2 O2 ) as a useful chemical has a wide range of applications, and the development of efficient semiconducting materials for H2 O2 production is deemed as a promising strategy to realize the energy conversion. In this paper, Cdx Zn1-x S (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) nano-branches are fabricated and the piezocatalytic and photocatalytic H2 O2 evolution performance are studied. Under ultrasound condition, the H2 O2 yield of as-synthesized solid solutions is all higher than those of pristine ZnS and CdS, and optimal evolution rate achieves 21.9µmol g-1 h-1 for Cd0.5 Zn0.5 S without any sacrificial agent, while it is increased to 151.6µmol g-1 h-1 under visible light irradiation. The piezo/photoelectrochemical tests, piezoresponse force microscopy (PFM), and computational simulation reveal that the nano-branch structure benefits the mechanical energy conversion more, favoring the H2 O2 evolution for Cd0.5 Zn0.5 S, and a higher concentration of charge carriers is generated in photocatalysis. The active radical trapping and in situ electron spin resonance (ESR) experiments demonstrate that both of the H2 O2 generation pathways are originated from oxygen reduction by the sequential two-step single-electron reaction. This work opens a door for promoting the H2 O2 production from nanostructure and solid solution design.

Synergetic effects by Co2+ and PO43- on Mo-doped BiVO4 for an improved photoanodic H2O2 evolution

The efficiency of hydrogen peroxide evolution reaction (H2O2ER) by photoanodic water oxidation is normally limited by low yield and poor selectivity. In this work, the surfaces of Mo doped BiVO4 are modified by Co2+ and PO43- ions (CPMB), which has been used as the photoanode with improved H2O2 yield and selectivity. The optimal evolution rate of the CPMB is ca. 0.23 µmol·min−1·cm−2, corresponding to 2.5 times to the pristine BiVO4 photoanode, and the faradaic efficiency of CPMB photoanode for H2O2ER is ca. 26%. In this study, the mechanism for the improved H2O2 evolution performance of CPMB has been investigated, indicating that PO43- ions mainly promote the formation of the •OH by dissociation of H2O, while Co2+ ions accelerate the conversion of the •OH for the subsequent H2O2 evolution. This study offers the strategy for designing an efficient photoelectrochemical system with optimized solar conversion efficiency for H2O2 production.

Cooperation of Congenital and Acquisitus Sulfur Vacancy for Excellent Photocatalytic Hydrogen Peroxide Evolution of CDS Nanorods from Air

Cooperation of Congenital and Acquisitus Sulfur Vacancy for Excellent Photocatalytic Hydrogen Peroxide Evolution of CDS Nanorods from Air

Influence of Oxygen Vacancies and Surface Facets on Water Oxidation Selectivity toward Oxygen or Hydrogen Peroxide with BiVO4

Bismuth vanadate (BiVO4) is one of the most promising photoanode materials for water oxidation. However, the water oxidation mechanism and selectivity on the different surfaces of BiVO4 are still not well understood, partly because of the structural complexity introduced by the presence of oxygen vacancies in the material. Using density functional theory, we show that the (001) surface of BiVO4 with subsurface vacancies is the most suitable for the oxygen evolution reaction, whereas the pristine (011) surface favors the hydrogen peroxide evolution reaction. A mechanism by which the vacancies can be removed from the surface, thereby influencing the water oxidation selectivity, is also described. Our results thus emphasize the crucial impact of the local structure on the catalytic selectivity in ternary oxides.

Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution

Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 μmol L−1 h−1 in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment.

Combined anode processes in sulfuric acid solutions

Etching of carbon steel products in sulfuric acid solutions is, on the one hand, a common process in mechanical engineering and, on the other hand, harmful to the environment. As the concentration of H2SO4 decreases and the solution becomes saturated with Fe2SO4, the etching rate of the oxide film on the steel surface decreases. Therefore, while reducing the H2SO4 concentration to 25-30 g/l etching process is stopped, and replacing the etching solution. In this case, the concentration of Fe2SO4 reaches 400 g/l. During etching, two processes are observed: dissolution of oxides and dissolution of iron, which is located under the layer of oxides. These two processes can run simultaneously. The study of electrode processes in sulfuric acid solutions containing inorganic and organic impurities is the basis for the development of technological parameters for the regeneration of spent sulfate solutions. For the study used a little wear anode materials - platinum and lead oxide (IV). To determine the kinetic regularities of the anode process in selected anode materials, voltammetry was used with the construction of the obtained dependences in Tafel coordinates. The polarization dependences consist of two rectilinear sections with an inflection at logia ≈ -1,8 (ia, A · cm-2). The slope of the first section does not depend on the H2SO4 concentration and is 120 mV. The slope of the second section, for solutions with an H2SO4 concentration of 0,05 ... 0,37 mol/dm-3, is 60 mV, and for a concentration of 2,5 mol/dm-3 - 71 mV. A change in the concentration of sulfuric acid has practically no effect on the polarization of the anode. At a concentration of 5,0 mol·dm-3, in the area of high current density (≥ 1500 A∙m-2), the potential of the anode exceeds the PZCh for lead dioxide. This promotes the adsorption of sulfate ions on the surface of the composite anode and the onset of active oxygen formation. Under these conditions, the evolution of hydrogen peroxide is observed on the platinum anode. The polarization dependences consist of two straight sections with different slopes. For the entire range of sulfuric acid concentrations, at low current density portion is observed with a slope of 120 mV. Concentration of sulfuric acid at this site does not affect the kinetics of the process that corresponds to the literature data for platinum. The zero order in pH and independence from the concentration of sulfuric acid for this site indicates that the most probable mechanism of oxygen evolution is water rarefaction. The obtained values of the effective activation energy of the oxygen evolution process on the LOTC are close to the results obtained on platinum – 41,8 kJ mol-1 at Ea = 1,95 V. The value of the effective activation energy indicates the electrochemical nature of polarization, and its decrease with an increase in the anodic potential indicates a decrease in the strength of the bond between oxygen and the LOTC surface.

Photochemical evolution of hydrogen peroxide on lignins

Means of sustainable on-demand hydrogen peroxide production are sought after for numerous industrial, agricultural, and environmental applications.

Organic thin film photofaradaic pixels for on-demand electrochemistry in physiological conditions.

We report ultrathin organic photovoltaic elements optimized to run photofaradaic reactions in biological conditions. We demonstrate concurrent oxygen reduction to hydrogen peroxide and glucose oxidation. The devices are powered by deep-red irradiation in the tissue transparency window. We utilize bilayers of phthalocyanine, acting as the light absorber, and perylene diimide, functioning as both electron-acceptor and the hydrogen peroxide evolution electrocatalyst. These heterojunction bilayers are stable when irradiated in simulated physiological conditions, producing photovoltages sufficient to simultaneously drive cathodic oxygen reduction to H2O2 and anodic oxidation of glucose. We find that optimization of the anode metal is critical for sustained photofaradaic reactivity. Our results demonstrate a robust "wet" thin film photovoltaic with potential for physiological applications where localized electrochemical manipulation is desired, in particular the delivery of reactive oxygen species.