H2O2 Production Activity Research Articles

Combustion synthesis of TiO2/C composites for enhanced photocatalytic H2O2 production and solar steam evaporation efficiency

In this work, a simple combustion method was proposed for the controllable synthesis of TiO2/C composites, which can achieve both the efficient solar water evaporation at the interface and photocatalytic H2O2 production. Structural and morphological characteristic indicated the co-existence of carbon quantum dots and amorphous carbon, which were well distributed on the surface of the TiO2. TiO2/C composites displayed the enhanced visible light absorption and the rapid separation of photogenerated electron-hole pairs. TiO2/C-10 exhibited an excellent photocatalytic H2O2 production activity of 3068.46 μmol/g/h under the simulated solar irradiation. Besides, its water evaporation rate reached up to 5.81 kg·m−2·h−1 under the simulated solar irradiation.

Platinum-induced nanolization and electron-deficient gold in platinum@gold cocatalyst for efficient photocatalytic hydrogen peroxide production

Simultaneous optimization of the number and intensity of oxygen (O2) adsorption on gold (Au) cocatalyst is highly required to greatly improve their interfacial hydrogen peroxide (H2O2)-production activity. However, it is a great challenge to realize the above effective modulation of Au by traditional photodeposition route. In this study, a platinum (Pt)-induced selective photodeposition method was designed to simultaneously regulate the particle size and electronic structure of Au cocatalyst for boosting the photocatalytic H2O2-production activity of bismuth vanadate (BiVO4) via the selective deposition of Pt@Au core–shell cocatalyst. The photocatalytic results indicate that the as-prepared BiVO4/Pt0.1@Au photocatalyst achieves a considerable H2O2-production activity with a rate of 2752.13 μmol L−1 (AQE = 13.76 %), which is obviously higher than that of BiVO4/Pt (137.63 μmol L−1) and BiVO4/Au (475.33 μmol L−1). It was found that the introduction of Pt successfully induced the formation of Au nanoparticles for enhancing the number of O2 adsorption. Meanwhile, the spontaneous transfer of free electrons of Au to Pt induces the generation of electron-deficient Auδ+ sites, which spontaneously enhances the O2-adsorption intensity for facilitating the 2-electron oxygen reduction reaction (ORR), resulting in efficient H2O2 production. The present strategy may be useful for more comprehensively regulating the intensity and number of O2 adsorption on cocatalysts to facilitate artificial photosynthesis.

Vacancy-defect promoting blue LED-driven H2O2 synthesis on Zn0.4Cd0.6S without additional cocatalysts

Photocatalytic synthesis of hydrogen peroxide offers an effective solution to the energy crisis. The design and development of high-activity and low-cost photocatalysts are crucial for H2O2 production. In this work, Zn0.4Cd0.6S with abundant S vacancies (SV-ZCS) is developed for H2O2 photosynthesis under 405 nm LED illumination without additional cocatalysts. The S vacancies serve as photo-generated electron trap centers, effectively extending the lifetimes of photogenerated carriers and promoting the separation of photoelectric carriers. Additionally, SV-ZCS is endowed with enhanced light capture capability, enhancing the overall photocatalytic activity for H2O2 production. The results were in line with expectations, the SV-ZCS samples demonstrated a hydrogen peroxide (H2O2) productivity of 3902 μmol L-1 h-1 when subjected to visible light irradiation, representing a significant increase compared to that of ZCS (2840 μmol L-1 h-1 ). This work provides an effective strategy for preparing photocatalysts for efficient hydrogen peroxide production.

Molecular Engineering of Metal–Organic Frameworks for Boosting Photocatalytic Hydrogen Peroxide Production

AbstractThe development of novel metal–organic frameworks (MOFs) as efficient photocatalysts for hydrogen peroxide production from water and oxygen is particularly interesting, yet remains a challenge. Herein, we have prepared four cyclic trinuclear units (CTUs) based MOFs, exhibiting good light absorption ability and suitable band gaps for photosynthesis of H2O2. However, Cu‐CTU‐based MOFs are not able to photocatalyzed the formation of H2O2, while the alteration of metal nodes from Cu‐CTU to Ag‐CTU dramatically enhances the photocatalytic performance for H2O2 production and the production rates can reach as high as 17476 μmol g−1 h−1 with an apparent quantum yield of 4.72 %, at 420 nm, which is much higher than most reported MOFs. The photocatalytic mechanism is comprehensively studied by combining the isotope labeling experiments and DFT calculation. This study provides new insights into the preparation of MOF photocatalysts with high activity for H2O2 production through molecular engineering.

Molecular Engineering of Metal-Organic Frameworks for Boosting Photocatalytic Hydrogen Peroxide Production.

The development of novel metal-organic frameworks (MOFs) as efficient photocatalysts for hydrogen peroxide production from water and oxygen is particularly interesting, yet remains a challenge. Herein, we have prepared four cyclic trinuclear units (CTUs) based MOFs, exhibiting good light absorption ability and suitable band gaps for photosynthesis of H2O2. However, Cu-CTU-based MOFs are not able to photocatalyzed the formation of H2O2, while the alteration of metal nodes from Cu-CTU to Ag-CTU dramatically enhances the photocatalytic performance for H2O2 production and the production rates can reach as high as 17476 μmol g-1 h-1 with an apparent quantum yield of 4.72 %, at 420 nm, which is much higher than most reported MOFs. The photocatalytic mechanism is comprehensively studied by combining the isotope labeling experiments and DFT calculation. This study provides new insights into the preparation of MOF photocatalysts with high activity for H2O2 production through molecular engineering.

TpPa-1/{0 1 0}-BiVO4 S-scheme heterojunction fabricated on specific crystal facets for highly efficient H2O2 artificial photosynthesis

The rational fabrication of inorganic–organic S-scheme heterojuncion hybrid photocatalysts on specific crystal facets is challenging but significant. Herein, we report that TpPa-1-covalent organic framework (COF) selectively grown on {010} crystal facets of decahedral BiVO4 (TpPa-1/{010}-BVO, denoted as TB-1) was synthesized through a surfactant-assisted microwave solvothermal route. The experimental results and theoretical calculations showed that TB-1 was more beneficial to separation of photogenerated carriers than the heterojunction randomly formed at all crystal facets ({010} + {110}) of BiVO4 (TpPa-1/BVO, denoted as TB-2). As a result, photocatalytic oxygen reduction reaction (ORR) activity for H2O2 production over TB-1 reached 723 μmol·gcat−1·h−1, which is 72.3-times, 5.7-times, and 2.4-times higher than individual BiVO4 (10 μmol·gcat−1·h−1), TpPa-1 (127 μmol·gcat−1·h−1), and TB-2 (305 μmol·gcat−1·h−1). In addition, the introduction of TpPa-1 could inhibit the decomposition of H2O2. This study not only provides a new hybrid photocatalyst for artificial H2O2 production but also highlights the importance of crystal facet engineering in the design of highly efficient photocatalysts.

Heterostructure engineering of resorcinol-formaldehyde resins and sulfur-vacancy-containing Zn3In2S6 for high-efficiency photocatalytic H2O2 production

Resorcinol-formaldehyde (RF) resins have garnered significant interest due to their remarkable efficiency in producing photocatalytic H2O2. The combination of RF with inorganic semiconductors to create organic–inorganic heterojunctions represents a promising strategy for enhancing photocatalytic activity. In this work, RF was coated onto Zn3In2S6 nanoflowers with sulfur-vacancy, creating RF/Zn3In2S6 composites with an S-scheme heterostructure. This novel composite exhibited superior photocatalytic activity for H2O2 production in both pure water and seawater, without sacrificial agents. Specifically, the production rate of RF/Zn3In2S6-0.3 in pure water under simulated solar illumination achieved 3174.34 μmol/h/g, marking 8.53 and 4.17 times over RF and Zn3In2S6, respectively. Moreover, its photocatalytic activity in seawater reached an impressive 2290.81 μmol/h/g, 4.93 and 3.12 times greater than that of RF and Zn3In2S6, respectively. The enhanced photocatalytic activity is attributed to the S-scheme charge transfer mechanism, which facilitates efficient charge separation and amplifies redox capabilities. Both experimental and density function theory analyses confirm the S-scheme route in RF/Zn3In2S6-0.3 for photocatalytic H2O2 production. This study not only presents the first account of an organic semiconductor RF being employed in an S-scheme heterojunction interface but also introduces the surface sulfur-vacancy mediated S-scheme heterojunction strategy for photocatalytic H2O2 production, representing a significant advancement in the field.

Singlet oxygen species induced by colloidal crystalline carbon nitride induced for efficient H2O2 synthesis with in situ antibacterial effect

Solar-driven hydrogen (H2) and hydrogen peroxide (H2O2) generation over visible-light responsive carbon nitride (CN) photocatalysts for in situ efficient sterilization is a promising and eco-friendly strategy. Herein, a colloidal potassium-ion (K+) intercalated crystalline CN nanosheets (KCCN) photocatalyst was constructed for boosting synergetic H2O2 synthesis with isopropanol (IPA) oxidation and in situ antibacterial effect. The surface hydroxyl (−OH) and cyano (−CN) groups induced by molten salt (KCl)-assisted thermal treatments contributed to the colloidal nature of CN, facilitating for high wettability of KCCN in aqueous solution to gain active hydrogen (H+) from water sustainably. Meaningfully, the enhanced high-energy singlet oxygen species (1O2) produced by KCNN-2 were verified by electron paramagnetic resonance (EPR) and 9,10-anthracenediyl-bis(methylene)-dimalonic acid (ABDA)-fluorescent probe, significantly contributing to H2O2 production and antibacterial effect. Consequently, the optimal KCCN-2 exhibited a much enhanced H2 generation of 4.11 mmol g−1 h−1, and H2O2 production activity of 1.82 mmol L−1 h−1 with acetone yield rate of 47.3 mmol g−1 h−1 under visible-light (λ > 420 nm) irradiation in 10 vol% IPA solution. The in-situ generated H2O2 can be activated to produce reactive oxygen species (ROS), especially 1O2, to effectively kill the Escherichia coli, reaching an improved an antibacterial rate of 89.7% under stimulated sunlight irradiation in 1 h. This work could offer a new insight into the photoinduced ROS for aqueous H2O2 photosynthesis and antibacterial application.

Monolithic Z-scheme NiS2/In2S3@PDMS/NF gas diffusion photocatalyst with strong interfacial O2 accumulation effect for effective H2O2 production and Fenton demulsification

In this work, a monolithic NiS2/In2S3@PDMS/NF gas diffusion photocatalyst is elaborately designed and synthesized. The synergy of structure and component gives advantageous features to NiS2/In2S3@PDMS/NF, including hydrophobic hollow NiS2/In2S3@PDMS tubes and porous Ni foam for O2 confinement/enrichment, strong coupling Z-scheme heterointerface for electron-hole separation, and abundant active sites for H2O2 generation via dual-channel pathway. The monolithic NiS2/In2S3@PDMS/NF gas diffusion photocatalyst exhibits outstanding photocatalytic activity for H2O2 production in dichloromethane/water two-phase system, with a yield of 1435.4 μmol·gcat−1, which is 2.5 times higher than that of NiS2/In2S3@PDMS. This can be attributed to the synergistic effect of spatial confinement effect in hollow tubes, hydrophobic modification of catalyst surface and 3D porous breathable self-support substrate. Additionally, white solid H2O2 powder with strong oxidizing property is obtained for reducing costs and increase safety in storage and transportation. Then, a fast and universal smartphone-assisted colorimetric method is constructed to quantitatively detect H2O2 on-site. Besides, NiS2/In2S3@PDMS/NF also exhibits a remarkable demulsification effect on SDS-stabilized oil-in-water emulsion through photocatalytic-Fenton degradation of SDS with “Two Birds One Stone” strategy, which is important for petroleum industry and environmental remediation.

Regulation of d-band center of TiO2 through fluoride doping for enhancing photocatalytic H2O2 production activity

Titanium dioxide (TiO2) has received extensive attention for photocatalytic hydrogen peroxide (H2O2) production, with the d-band center related to the adsorption performance, which affects the photocatalytic reaction process. Herein, an ingenious strategy to lower the antibonding-orbital occupancy in the Ti 3d orbital by fluoride ion (F−) doping is proposed, with density functional theory calculations predicting that F-doping into TiO2 induces a non-uniform charge distribution and enables an upshift of the d-band center in F/TiO2. This manipulation provides accessible active centers with favorable d-band energy levels, which can improve the charge-transfer behavior, strengthen the interaction between the adsorbed oxygen and the photocatalyst, and reduce the adsorption energy of oxygen, eventually promoting the photocatalytic H2O2 production rate. The experimental results further confirm that a lower antibonding-orbital occupancy can intensify the adsorption of atomic oxygen at the Ti sites. Electron paramagnetic resonance experiment reveals that the presence of F− ions in the lattice induces the formation of Ti3+ centers that localize the extra electron needed for charge compensation. Femtosecond transient absorption (fs-TA) spectroscopy suggests that photogenerated electrons are transferred from the conduction band of F/TiO2 to the Ti3+ surface states and surface F− ions, expediting the separation of electrons and holes. Consequently, with F− doping in TiO2, the photocatalytic H2O2 production yields improved from 277 to 467 μmol·g−1·h−1, with ethanol as a sacrificial reagent. This study provides a new strategy for regulating the d-band center to optimize the adsorption strength between the photocatalyst and oxygen atoms and achieve enhanced photocatalytic H2O2 production performance.

Bi, K co-doped graphitic phase carbon nitride for efficient photocatalytic H2O2 production

The emerging photocatalytic production of hydrogen peroxide (H2O2) using graphitic carbon nitride (g-C3N4) has attracted a lot of attention for its potential applications in various fields. However, However, the catalytic activity of pure g-C3N4 is still limited. Herein, Bi, K co-doped g-C3N4 (BixKy-CN) was prepared by co-thermal polymerization of a mixture of potassium nitrate, bismuth nitrate, melamine, and urea. The obtained Bi3.6K3-CN composite possesses more negative conduction and valence band positions that can, to some extent, enhance photocatalytic performance by lowering the energy barrier of redox reactions and by enhancing electron absorption capacity. Additionally, the pyrolysis process of the potassium nitrate and bismuth nitrate has a considerable impact on the formation of the morphology of g-C3N4, generating a porous lamellar-structure with nitrogen defects, resulting in increased oxygen adsorption and utilization capacity. These synergistic effects enable Bi3.6K3-CN to exhibit excellent photocatalytic activity and cycling stability for H2O2 production. After 3 hours of visible light irradiation, the production of H2O2 catalyzed by Bi3.6K3-CN can reach 1207.72 μmol L-1, which is 57 times higher than that of pure g-C3N4.

Pauling-type adsorption of O2 induced by S-scheme electric field for boosted photocatalytic H2O2 production

The effective adsorption of oxygen (O2) molecules over photocatalysts is a critical step in promoting the performance of photocatalytic H2O2 production. However, g-C3N4 usually features a Yeager-type (side-on) adsorption configuration of O2 molecules, which causes the breaking of O–O bonds and severely hinders the H2O2 production activity. Herein, we synthesized an oxygen-vacancy-rich TiO2–x/g-C3N4 step-scheme (S-scheme) heterojunction to regulate the oxygen adsorption configuration and improve the 2e– ORR selectivity of H2O2 production. In-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations reveal that the S-scheme heterojunction is formed between TiO2–x and g-C3N4. The difference between their Fermi levels leads to the electron flow from g-C3N4 to TiO2–x, which increases the electron-deficient sites in g-C3N4. As a result, the cleavage of O–O bonds on the surface of g-C3N4 is avoided and the oxygen adsorption configuration is tuned from Yeager-type to Pauling-type (end-on). Consequently, the photocatalytic H2O2 production rate is dramatically improved to 1780.3 μmol h–1, which is about 5 times higher than that of pristine g-C3N4. This work paves a new way to tailor the oxygen adsorption configuration by rationally designing S-scheme heterojunction photocatalysts.

COF/In2S3 S-Scheme Photocatalyst with Enhanced Light Absorption and H2O2-Production Activity and fs-TA Investigation.

Photocatalytic hydrogen peroxide (H2O2) synthesis from water and O2 is an economical, eco-friendly, and sustainable route for H2O2 production. However, single-component photocatalysts are subjected to limited light-harvesting range, fast carrier recombination, and weak redox power. To promote photogenerated carrier separation and enhance redox abilities, an organic/inorganic S-scheme photocatalyst is fabricated by in situ growing In2S3 nanosheets on a covalent organic framwork (COF) substrate for efficient H2O2 production in pure water. Interestingly, compared to unitary COF and In2S3, the COF/In2S3 S-scheme photocatalysts exhibit significantly larger light-harvesting range and stronger visible-light absorption. Partial density of state calculation, X-ray photoelectron spectroscopy, and femtosecond transient absorption spectroscopy reveal that the coordination between In2S3 and COF induces the formation of mid-gap hybrid energy levels, leading to smaller energy gaps and broadened absorption. Combining electron spin resonance spectroscopy, radical-trapping experiments, and isotope labeling experiments, three pathways for H2O2 formation are identified. Benefited from expanded light-absorption range, enhanced carrier separation, strong redox power, and multichannel H2O2 formation, the optimal composite shows an impressive H2O2-production rate of 5713.2µmol g-1 h-1 in pure water. This work exemplifies an effective strategy to ameliorate COF-based photocatalysts by building S-scheme heterojunctions and provides molecular-level insights into their impact on energy level modulation.

B–F dual-doped carbon nanotubes for multi-site and high-rate two-electron oxygen reduction reaction electrocatalysis

Electrocatalytic two-electron oxygen reduction reaction (2e−-ORR) to produce hydrogen peroxide (H2O2) is a promising green way to replace the conventional anthraquinone reaction. Non-metallic catalysts are considered as low-cost catalysts due to their excellent stability and versatile surface chemistry. The performance of non-metallic electrocatalysts is usually limited by the limited catalytic active sites on the surface. Here, we report fluorine and boron dual-doped carbon nanotubes (B–F–C) as a metal-free electrocatalyst for H2O2 production, fabricated via a fast microwave treatment. With the synergistic effect of F and B, this strategy can effectively convert carbon and boron atoms on carbon nanotubes into highly active sites. As a result, an H2O2 yield up to 24.3 mol g−1 L−1 is achieved over B–F–C with a stable selectivity of above 90% within 0.2–0.7 V vs. RHE in 0.1 M KOH. Density functional theory (DFT)calculations further confirm that the multiple active sites created by the dual doping of fluorine and boron are the key factor in improving the performance of 2e−-ORR electrocatalysis. Therefore, this work offers a promising prospect for the design and preparation of catalysts with high catalytic activity for H2O2 production and other catalytic areas of industrial significance.

Triple-Phase Photocatalytic H2O2 Production on a Janus Fiber Membrane with Asymmetric Hydrophobicity.

Photocatalytic O2 reduction is an intriguing approach to producing H2O2, but its efficiency is often hindered by the limited solubility and mass transfer of O2 in the aqueous phase. Here, we design and fabricate a two-layered (2L) Janus fiber membrane photocatalyst with asymmetric hydrophobicity for efficient photocatalytic H2O2 production. The top layer of the membrane consists of superhydrophobic polytetrafluoroethylene (PTFE) fibers with a dispersed modified carbon nitride (mCN) photocatalyst. Amphiphilic Nafion (Naf) ionomer is sprayed onto this layer to modulate the microenvironment and achieve moderate hydrophobicity. In contrast, the bottom layer consists of bare PTFE fibers with high hydrophobicity. The elaborate structural configuration and asymmetric hydrophobicity feature of the optimized membrane photocatalyst (designated as 2L-mCN/F-Naf; F, PTFE) allow most mCN to be exposed with gas-liquid-solid triple-phase interfaces and enable rapid mass transfer of gaseous O2 within the hierarchical membrane, thus increasing the local O2 concentration near the mCN photocatalyst. As a result, the optimized 2L-mCN/F-Naf membrane photocatalyst shows remarkable photocatalytic H2O2 production activity, achieving a rate of 5.38 mmol g-1 h-1 under visible light irradiation.

Single Zn Atoms with Acetate-Anion-Enabled Asymmetric Coordination for Efficient H2 O2 Photosynthesis.

Exploring unique single-atom sites capable of efficiently reducing O2 to H2 O2 while being inert to H2 O2 decomposition under light conditions is significant for H2 O2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn-N3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N4 sites when sulfate (SO4 ) is adopted (CN/Zn-SO4 ). Both experimental and theoretical investigations demonstrate that the Zn-N3 O moiety exhibits higher intrinsic activity for O2 reduction to H2 O2 than the Zn-N4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H2 O2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H2 O2 production activity under visible light irradiation.

Single Zn Atoms with Acetate‐Anion‐Enabled Asymmetric Coordination for Efficient H2O2 Photosynthesis

AbstractExploring unique single‐atom sites capable of efficiently reducing O2 to H2O2 while being inert to H2O2 decomposition under light conditions is significant for H2O2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single‐Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single‐Zn sites on CN, forming asymmetric Zn−N3O moiety on CN (denoted as CN/Zn−OAc), in contrast to the obtained Zn−N4 sites when sulfate (SO4) is adopted (CN/Zn−SO4). Both experimental and theoretical investigations demonstrate that the Zn−N3O moiety exhibits higher intrinsic activity for O2 reduction to H2O2 than the Zn−N4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H2O2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn−OAc catalyst exhibits significantly improved photocatalytic H2O2 production activity under visible light irradiation.

Synergy of oxygen vacancies and Bi nanoparticles on BiOBr nanosheets for enhanced photocatalytic H2O2 production

In situ Bi nanoparticle modified BiOBr nanosheets with tuned OVs were prepared via a facile one-pot solvothermal method. Benefiting from the in situ Bi modification and moderate surface OVs, the as-prepared photocatalysts showed enhanced H2O2 production activity.

Dual built-in spontaneous electric fields in an S-scheme heterojunction for enhanced photocatalytic H2O2 production

A facile photodeposition method was used to selectively modify Cu2O and MnOOH on BiVO4. The improved H2O2-production activity was mainly attributed to the dual built-in electric field in the BiVO4/Cu2O S-scheme heterojunction.

Reconstruction of D‐Π‐A Polymer Accelerating Photocatalytic Degradation of BPA and Production of H2O2

AbstractAdvanced oxidation processes (AOPs) using hydroxyl radicals (•OH) as oxidizing agents are a promising technology. Herein, a feasible strategy is developed to initially construct carbazole‐based D‐π‐A type conjugated polymer (PBNCZ) via the oxidative coupling. Additionally, introducing ─COO− through Cyano hydrolysis extends its conjugated structure and improves the energy band structure, which greatly facilitates the generation of •OH as well as the enrichment of pollutants. Detailed experiments and theoretical calculations have proved that the introduction of ─COO− enhances the adsorption of O2 and bisphenol A (BPA), optimizing the reaction path of •OH. Thus, it completely decomposes 10 ppm of BPA within just 10 min, exceeding all previously organic photocatalysts. Meanwhile, the efficiency of photocatalytic H2O2 production by PBNCZ‐COO− reaches 1719.03 µmol h−1 g−1 under visible light. This multifunctional material with high adsorption capacity, photodegradation efficiency, and photocatalytic H2O2 production activity provides a solid foundation for the preparation of organic photocatalysts.