Abundant Oxygen Functional Groups Research Articles

Achieving unprecedented cyclability of flowless zinc-bromine battery by nitrogen-doped mesoporous carbon on thick graphite felt electrode

The flowless zinc-bromine battery (FLZBB) is non-flammable as it is based on an aqueous electrolyte and is considered an alternative to redox flow batteries because of its cost-effectiveness using a simple cell platform. However, it faces challenges related to self-discharge caused by the crossover of bromine (Br2) and polybromide anions (Brn+2-) formed at the positive electrode during the charging process. The self-discharge reaction consumes the charging active materials, thereby decreasing battery performance and lifespan. To address the critical issues, this study introduces the development of a revolutionary positive electrode: a nitrogen-doped mesoporous carbon-coated thick graphite felt (NMC/GF). This positive electrode effectively suppresses the crossover of active materials and prevents the self-discharge reaction. The mesopores, strategically embedded with nitrogen sites, serve as a stronghold, capturing and immobilizing bromine and polybromide anions, significantly reducing their undesirable effects. Furthermore, we enhanced the electrochemical performance of the NMC/GF electrode by modifying it to be ultrahydrophilic. Abundant oxygen and nitrogen functional groups were incorporated onto the electrode, resulting in an amplified affinity with the aqueous electrolyte. This modification led to improved bromine redox reaction kinetics. Demonstrating an excellent Coulombic efficiency surpassing 96 % and an energy efficiency of over 76 % at a current density of 20 mA cm−2 with a high-rate areal capacity of 2 mAh cm−2, this novel positive electrode achieves a previously unattained milestone; cyclability unprecedentedly extended to 10,000 cycles. The development of NMC/GF positive electrodes further advances the FLZBB system, and large-area scale-up research of these carbon electrodes makes looking forward to practical uses in energy storage systems.

ZIF-8/balsa wood derived N-doped porous carbon as self-supporting electro-Fenton cathode for efficient antibiotics degradation

Efficient electrochemical advanced oxidation processes (EAOPs) based on carbon catalysts are highly promising candidates for green environmental remediation technologies. Wood derived N-doped porous carbon (WNPC) was prepared the balsa wood with in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) was used as precursor. WNPC acted as self-supporting electric Fenton cathode with high yield and selectivity (96 %) of in-situ H2O2 generation, which effectively avoided the use binder for powder material. Owing to abundant N-doping and oxygen functional groups, the H2O2 yield of WNPC was three times that of balsa wood derived carbon (WC) in electro-Fenton system. The graphite-N promoted the electron transfer, while the pyridinic-N could enhance the selectivity of the 2e-ORR for H2O2 generation. Furthermore, the specific surface area of WNPC was 10 times of WC, with improved hydrophilicity and accelerated electron transfer. The removal efficiency of tetracycline hydrochloride (TC) achieved 91 % within 120 min in electro-Fenton system with WNPC and Fe2+, which was much higher than that with WC (63 %). Free radical scavenging and electron paramagnetic resonance experiments confirmed that ·OH and O2–· were the main active substances for TC degradation in electro-Fenton system. In addition, WNPC has good stability, reusability, and comparable degradation performance of various organic pollutants, and also had efficient degradation performance with actual water. This research proposed a novel strategy to construct efficient electro-Fenton catalyst with wood as precursor, which provides an advancing electrocatalytic methods to achieve efficient and environmentally conscious water purification.

Growing ZIF-L seeds in graphene oxide interlayers towards synthesizing efficient cation sieving membranes

Designing and synthesizing membranes with fast and selective cation transport remains extremely challenging. Herein, ZGO membranes are conceived via a two-dimensional zeolitic imidazolate framework (ZIF-L) in situ grown on graphene oxide (GO), with ZIF-L as an interlayer that increases both vertical interlayer spacing and lateral tortuous path spacing of GO, thus improving the stability, selectivity, and ion permeation of the ZGO lamellar membrane. Structural analyses reveal that GO surfaces with abundant oxygen functional groups favored the formation of ZIF-L with 316 crystal planes and offered a high ion-accessible surface area. More importantly, the ZGO membrane delivers an excellent K+ permeability of 86.9 mmol m−2 h−1 and K+/Mg2+ selectivity up to 266, outperforming state-of-the-art GO-based membranes. Furthermore, molecular simulations confirm that the hydrogen bonding between hydrated cations and polar functional groups of ZGO membranes substantially restricted the dynamical transport of bivalent cation, and thus led to excellent cation selectivity. These results open a pathway to developing membranes for fast and highly selective ion separations in the future.

Preparation of highly adsorptive biochar by sequential iron impregnation under refluxing and pyrolysis at low temperature for removal of tetracycline

Iron-doping modification is a prevailing approach for improving adsorption capability of biochar with environmental friendliness, but usually requires high temperature and suffers from iron aggregation. Herein, a highly adsorptive biochar was manufactured via sequential disperse impregnation of iron by refluxing and pyrolysis at low temperature for eliminating tetracycline (TC) from aqueous solution. Iron oxides and hydroxides were impregnated and stably dispersed on the carbon matrix as pyrolyzed at 200 °C, meanwhile abundant oxygen and nitrogen functional groups were generated on surface. The iron-doped biochar exhibited up to 891.37 mg/g adsorption capacity at pH 5, and could be recycled with high adsorption capability. The adsorption of TC should be mostly contributed to the hydrogen bonding of N/O functional groups and the hydrogen bonding/coordination of iron oxides/hydroxides. This would provide a valuable guide for dispersedly doping iron and conserving functional groups on biochar, and a super iron-doped biochar was prepared with superior recyclability.

Phoshporic acid actived biochar for efficient removal of paclobutrazol and alleviating its phytotoxicity to mung bean

Using biochar to absorb organic pollutants in water and soil is a simple and efficient method. However, most biochar is typically prepared at high temperatures (>500 ℃), resulting in low yield and high production costs and hence limiting its practical applications. This study aimed to prepare biochar (P-BC) through low-temperature (280 ℃) phosphoric acid assisted pyrolysis of cotton stalks. P-BC possessed a large specific surface area (389.96 m2·g−1) and contained abundant oxygen functional groups as well as phosphorous and nitrogen nutrient elements. This study applied P-BC to remove paclobutrazol (PBZ) from water and remediate PBZ-polluted soil. The water adsorption capacity of P-BC was 192.89 mg·g−1. The adsorption mechanisms of P-BC included pore filling, hydrogen bonding, weak electrostatic effects, and π-π interactions. Adding 1 % P-BC to soil contaminated with 10 mg·kg−1 PBZ could alleviate PBZ induced phytotoxicity in mung bean seedlings, ensuring the normal growth of roots and plants.

Biomorphic porous carbon derived from reed with enriched oxygen-functional groups for high-performance supercapacitors

Biomass derived porous carbons have been widely used as remarkable supercapacitor electrodes. To investigate the effects of biomass pretreatment on structures and properties of derived porous carbons, we proposed baking-mediated carbonization method firstly and prepared reed-derived oxygen-doped porous carbons. The baking pretreatment is proved to protect the oxygen functional groups from escaping in the reed-derived porous carbons. The resultant OPC800-B2 bio‑carbon shows a large Brunauer-Emmett-Teller (BET) surface area of 1650 m2·g−1, especially with abundant oxygen functional groups of 9.63 at.%, which can promote the ion transportation and enhance the capacitive performance. As supercapacitor electrode, OPC800-B2 exhibits a specific capacitance of up to 336.4 F·g−1 at 1 A·g−1, greatly higher than that of OPC800 without using baking pretreatment. The symmetric two-electrode device assembled with OPC800-B2 in sodium sulfate (Na2SO4) electrolyte affords a superb energy density of 18.66 Wh·kg−1 at a power density of 450 W·kg−1. An excellent cycling stability of 93 % is also observed after 10,000 cycles. The outstanding electrochemical behaviors are attributed to the microporous features with sufficient oxygen-active functional groups caused by baking-mediated preparation engineering. This simple and non-polluting approach provides a feasible and cost-effective way to synthesize the functional biomass-derived porous carbons for energy applications.

Fabrication of N, O dual-doped ultra-microporous carbon from microalgae for efficient CO2 capture via deep eutectic solvent-assisted hydrothermal carbonization

A novel approach for porous carbon fabrication from microalgae is presented for efficient CO2 capture. Microalgae-derived hydrochar is produced through deep eutectic solvent-assisted hydrothermal carbonization (DES-HTC), followed by chemical activation to obtain N, O dual-doped ultra-microporous carbon. The finalized carbon exhibited high nitrogen content (3.92%), oxygen content (21.46%), and ultra-micropore volume (0.25 cm3/g). Subsequently, it exhibited excellent CO2 adsorption capacity (4.37 mmol/g) and CO2/N2 selectivity (32) at 25 °C and 1 bar. Equilibrium and in-situ FTIR spectra of CO2 adsorption substantiated that the synergy between the abundant oxygen and nitrogen functional groups and the ample ultra-micropores significantly enhanced the capacity. Characterization of hydrochar indicated that the addition of DES during HTC effectively accelerated the Maillard reaction, facilitating the insertion of nitrogen and oxygen atoms into the carbon matrix and reducing their loss in subsequent chemical activation. Furthermore, DES was found to increase thermally unstable oxygen functional groups during HTC, promoting in ultra-micropore formation during activation. These findings provide a framework for advancing microalgae-based carbon materials in CO2 capture applications.

Facile and sustainable synthesis of sugarcane-derived binderless self-supported porous carbon membrane for advanced electrode materials

Powder biomass-derived electrodes have been extensively explored and used in capacitor devices, but there are still problems in practice, such as complicated electrode assembly processes and insufficient capacitance with larger current density. We proposed an advanced approach for producing porous carbon membranes derived from sugarcane that could be directly mounted as flexible binderless self-supported electrodes. A sugarcane-derived porous carbon membrane (SPCM) was simply prepared by freeze-drying followed and carbonization with KOH as an activator. The specific surface area of SPCM was 459.5 m² g−1, and the main elements were N (2.05 at%), O (21.45 at%), and C (73.62 at%). Compared with other biomass materials, it possessed a highly porous, multi-level structure and contained abundant nitrogen and oxygen functional groups, which facilitate ion adsorption and rapid electron transfer. Consequently, the symmetrical SPCM electrodes exhibit favorable electrochemical characteristics, at a current density of 0.5 A g−1, the specific capacitance measured at 248.0 F g−1. Additionally, the energy density reached 8.6 Wh kg−1 at a power density of 83.3 W kg−1, and the power density of 1666.7 W kg−1 was attained at an energy density of 1.9 Wh kg−1.

Microwave-assisted green synthesis of monodispersed carbon micro-spheres and their antibacterial activity

Well-dispersed mono-carbon microspheres were synthesized via the hydrothermal carbonization of ascorbic acid (AA) using a microwave reactor without adding any catalyst. The synthesized materials were characterized by various microscopic and spectroscopic techniques (e.g., SEM, TEM, XRD, Raman, XPS, EDX, and FTIR spectroscopy), showing that the formed carbon spheres (CSs) exhibited uniform morphology and surface structure with abundant oxygen functional groups. The dimension of the formed CSs could be easily tuned by altering the AA concentration, reaction time, and temperature. A mechanism for the formation of the CSs was proposed, and their antibacterial activities were also investigated against two bacterial strains, showing the inhibition rate of 94% for E. coli and 100% for S. aureus. This biocidal activity was achieved with the pure CSs produced from the inexpensive AA (Vitamin C) via a rapid green process without any further surface modification or doping, thus promising for myriad surface coating, medical and environmental applications.

Oxidized Graphitic-C3N4 with an Extended π-System for Enhanced Photoelectrochemical Property and Behavior

In this work, an oxidized g-C3N4 film was successfully synthesized using a two-step acid treatment and electrophoretic deposition method. The delocalized π-system of the oxidized g-C3N4 film was extended via an annealing treatment. We investigated the influence of hydrogen bonding reversibility and the oxidation treatment of g-C3N4 on the photoelectrochemical property and photocathodic protection for 304 stainless steel (304 SS). The resulting oxidized g-C3N4 photoelectrode with an extended π-system presents a remarkably enhanced photogenerated electron transfer capability from the photoelectrode to 304 SS (photoinduced OCP negative shift of −0.55 VAgCl) compared with oxidized g-C3N4 and protonated g-C3N4. The oxidation of g-C3N4 facilitates the formation of a porous structure and the introduction of abundant oxygen functional groups, which could promote the effective separation and transport of photogenerated electron–hole pairs. The hydrogen bonding reversibility contributes to the extension of the delocalized π-conjugation system, which could enhance light absorption efficiency. Meanwhile, the annealing treatment is beneficial for prolonging the lifetime of photoelectrons, which could reduce the recombination rate of charge carriers. In addition, to understand how the oxidation treatment and annealing treatment affect the charge transfer behavior, the electronic band structure was investigated, and we found that the oxidized g-C3N4 film with an extended π-system possesses a more negative conduction band position, which could reduce the energy barrier of the photogenerated electron transfer.

Electrochemical Fine-Tuning of the Chemoresponsiveness of Langmuir-Blodgett Graphene Oxide Films.

Graphene oxide has been widely deployed in electrical sensors for monitoring physical, chemical, and biological processes. The presence of abundant oxygen functional groups makes it an ideal substrate for integrating biological functional units to assemblies. However, the introduction of this type of defects on the surface of graphene has a deleterious effect on its electrical properties. Therefore, adjusting the surface chemistry of graphene oxide is of utmost relevance for addressing the immobilization of biomolecules, while preserving its electrochemical integrity. Herein, we describe the direct immobilization of glucose oxidase onto graphene oxide-based electrodes prepared by Langmuir-Blodgett assembly. Electrochemical reduction of graphene oxide allowed to control its surface chemistry and, by this, regulate the nature and density of binding sites for the enzyme and the overall responsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectron spectroscopy, surface plasmon resonance, and electrochemical measurements were used to characterize the compositional and functional features of these biointerfaces. Covalent binding between amine groups on glucose oxidase and epoxy and carbonyl groups on the surface of graphene oxide was successfully used to build up stable and active enzymatic assemblies. This approach constitutes a simple, quick, and efficient route to locally address functional proteins at interfaces without the need for additives or complex modifiers to direct the adsorption process.

Engineering of the microstructures of enzymatic hydrolysis lignin-derived hard carbon anodes for sodium-ion batteries

Hard carbon is considered as the most commercially applicable anode for sodium-ion batteries. Lignin has the characteristics of sustainable, low cost, high carbon content (>60%) and abundant oxygen functional groups, which is expected to be used as a promising candidate precursor for low-cost hard carbons. The structure and electrochemical performances of hard carbons could be regulated by adjusting carbonization temperature. The microstructure and electrochemical performance of LDHC anode are highly dependent on the carbonization temperature. Increasing carbonization temperature could reduce specific surface area and improve initial coulombic efficiency. The slope and plateau capacity of the LDHC anode could also be adjusted by changing the carbonization temperature. The LDHC prepared at 1200 °C showed the best sodium-ion storage performance, with an initial coulombic efficiency of 78.9% and a reversible sodium-ion storage capacity of 284.7 mAh g−1.

Wet-Process-Modified Blue-Green Algae Biochar by K2FeO4 for the Efficient Adsorption of Cr(VI) from Water

Iron-modified biochar adsorbent shows its promise for removing Cr(VI) from water. However, the traditional dry-grinding modification methods to prepare iron-modified biochar (DFeBC) usually result in the aggregation of iron oxide particles, thus impeding the adsorption capacity. Herein, blue-green algae waste derived biochar modified in a wet process by K2FeO4 (WFeBC) was developed, and it showed well-distributed iron oxide on the surface of the biochar. As a result, WFeBC displayed a larger theoretical adsorption capacity of 66.22 mg/g than that of DFeBC (48.54 mg/g). It was found that the uniform-distributed iron oxide and abundant oxygen functional groups of WFeBC played an important role in the removal process of Cr(VI). In the adsorption process, the reduction of Cr(VI) to Cr(III) by Fe(II) promoted the removal of hexavalent chromium. The Cr(VI) will be attracted by protonated oxygen functional groups through electrostatic interaction and complexation in an acid environment. All the results show that the wet modification of biochar by K2FeO4 can effectively improve the removal ability of WFeBC to Cr(VI).

Metal-free electro-Fenton degradation of perfluorooctanoic acid with efficient ordered mesoporous carbon catalyst

Heterogeneous electro-Fenton with in situ generated H2O2 and •OH is a cost-effective method for the degradation of refractory organic pollutants, in which the catalyst is an important factor affecting its degradation performance. Metal-free catalysts can avoid the potential risk of metal dissolution. However, it remains great challenge to develop efficient metal-free catalyst for electro-Fenton. Herein, ordered mesoporous carbon (OMC) was designed as a bifunctional catalyst for efficient H2O2 and •OH generation in electro-Fenton. The electro-Fenton system showed fast perfluorooctanoic acid (PFOA) degradation with kinetics constant of 1.26 h−1 and high total organic carbon (TOC) removal efficiency of 84.0 % after 3 h reaction. The •OH was the main species responsible for PFOA degradation. Its generation was promoted by the abundant oxygen functional groups such as C-O-C and the nano-confinement effect of mesoporous channels on OMCs. This study indicated that OMC is an efficient catalyst for metal-free electro-Fenton system.

Enhanced flow-through electro-Fenton process based on rGO aerogel cathode: Essential role of sodium tetrapolyphosphate

As a promising advanced oxidation process, electro-Fenton (EF) technology could in-situ generate H2O2 through 2e- oxygen reduction reaction (ORR), and then activate H2O2 into reactive oxygen species to degrade the organic pollutants in wastewater. However, its practical application is limited by the sluggish ORR kinetics and acidic condition (pH < 3), which requires external addition of acids, ferrous salts (FeII) or even H2O2. To improve the efficiency of wastewater treatment, targeted development on EF technology based on specific application scenario is also critical. In this contribution, a flow through EF system was developed to remove the antibiotic pollutants in the meat processing wastewater, where the EF process was significantly enhanced by the reduced graphene oxides (rGO) aerogel cathode and the presence of polyphosphates (PPs). The interconnected 3D porous configuration of rGO aerogel with abundant oxygen functional groups greatly facilitated the mass and electron transfer during the flow-through EF process. Meanwhile, the formation of PPs film on the surface of sacrificial iron anode ensured continuous releasing of FeII under near-neutral condition without rusting, and the generation of FeII-PPs complexes effectively compensated the production of H2O2 via the pathway of molecular oxygen activation. Moreover, 99.9% of phosphorus can be recycled and reused in the flow-through EF system by coupling the nanofiltration technology, enabling efficient removal of antibiotics and utilization of PPs in the wastewater.

Hydrogen Stabilization and Activation of Dry-Quenched Coke for High-Rate-Performance Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) have rapidly come to dominate the market owing to their high power and energy densities. However, several factors have considerably limited their widespread commercial application, including high cost, poor high-rate performance, and complex synthetic conditions. Herein, we use earth-abundant and low-cost dry-quenched coke (DQC) to prepare low-crystalline carbon as anode material for LIBs and tailor the carbon skeleton via a facile green and sustainable hydrogen treatment. In particular, DQC is initially pyrolyzed at 1000 °C, followed by hydrogen treatment at 600 °C to obtain C−1000 H2−600. The resultant C−1000 H2−600 possesses abundant active defect sites and oxygen functional groups, endowing it with high-rate capabilities (C−1000 H2−600 vs. commercial graphite: 223.98 vs. 198.5 mAh g−1 at 1 A g−1 with a capacity retention of about 72.79% vs. 58.05%, 196.97 vs. 109.1 mAh g−1 at 2 A g−1 for 64.01% vs. 31.91%), and a stable cycling life (205.5 mAh g−1 for 1000 cycles at 2 A g−1) for LIBs. This proves that as a simple moderator, hydrogen effectively tailors the microstructure and surface-active sites of carbon materials and transforms low-cost DQC into high-value advanced carbon anodes by a green and sustainable route to improve the lithium storage performance.

Intrinsic Carbon Defects for the Electrosynthesis of H2O2.

Carbon materials have manifested promising potential in electrochemical reduction of O2 to H2O2. The oxygen functional groups have been identified as the catalytic sites. However, the intrinsic carbon defects abundant in carbon materials have often been neglected. Herein, a three-dimensional carbon framework with abundant intrinsic defects and oxygen functional groups (the oxygen content and chemical states of oxygen are comparable to those of commercial carbon black) was introduced and exhibited outstanding catalytic activity and selectivity toward H2O2 electrosynthesis. Through a combination of in situ Raman spectroscopy and density functional theory calculations, the intrinsic carbon defects, such as zigzag edge and zigzag pentagon sites with optimal binding energy for OOH, were also determined to be active sites. It was further revealed that intrinsic carbon defects with large negative charge density and asymmetric spin density may have high activity toward H2O2 production.

A metal-/additive-free system for oxygen-mediated hydroxylation of benzene over polyfuran-functionalized hydrothermal carbocatalyst

Direct benzene hydroxylation with dioxygen (O2) is among the most promising alternative pathways for green phenol production, but efficient catalysis systems usually involve metal species or other additives such as sacrificial agents. In this work, we designed a carbon catalyst from the hydrothermal treatment of biomass-derived sucrose and constructed a metal-/additive free heterogeneous catalytic system for benzene hydroxylation to phenol with O2. The champion carbon sample gave a high phenol yield of 13.4%. The catalyst was facilely recovered and reused without apparent deactivation. There abundant oxygen functional groups such as phenolic and quinone carbonyl groups served as the active sites and polyfuran units accelerated the O2 adsorption and activation. The synergistic effect of these surficial organic groups is conducive to the formation of reactive oxygen species, hydroxyl radicals, which effectively oxidized the benzene to phenol.

A surface network based on oxidative graphene oxide for the determination of hydroquinone and catechol in ground and wastewater samples

A sensing network based on oxidative graphene oxide (OGO) fabricated onto a glassy carbon electrode (GCE) by consecutive anodic treatment of a native synthesized surface materials called the virgin graphene oxide (VGO). The proposed oxidative step is crucial to decrease stacking interactions and enrichment the surface materials with oxygenated functionalities that play significant roles in improving the surface conductivity and electron transfer kinetics. A primary result achieved by electrochemical impedance spectroscopy (EIS) showed an exceptional reactivity of OGO-GCE interpreted by estimating the apparent rate constant (kapp) of electron transfer kinetics that approaches 8.7 times over VGO-GCE. The differential pulse voltammetry (DPV) experimental data for the simultaneous determination of hydroquinone (HQ) and catechol (CC) verify the remarkable reactivity of the OGO-GCE compared to both bare GCE and VGO-GCE. The above supportive evidences underlines the significance of abundant oxygen functional groups for fast kinetics at OGO surface materials. The selectivity test of OGO-GCE in the determination of HQ and CC under optimal conditions was excellently achieved at which the detection limit (DL3σ) of HQ and CC were 0.114 μM and 0.124 μM, respectively. The successful analytical performance of OGO on two water samples suggested the application of robust, stable and promising materials for trace HQ and CC quantification.

Hydrochar-mediated photocatalyst Fe3O4/BiOBr@HC for highly efficient carbamazepine degradation under visible LED light irradiation

• Hydrochar-mediated Fe 3 O 4 /BiOBr@HC was synthesized by a hydrolysis method. • Efficient carbamazepine removal benefited from synergistic effect of Fe 3 O 4 and HC. • Faster charge separation and more active species generation occurred with help of HC. • Active species include superoxide radicals, hydroxyl radicals, and photogenerated holes. • Three degradation pathways were proposed to indirectly verify the role of active species. Construction of composite photocatalysts with high charge transfer efficiency and fast surface catalytic reaction has recently gained huge interest. In this work, a hydrochar microsphere-mediated photocatalyst Fe 3 O 4 /BiOBr@HC with rapid surface catalytic reaction and electron transfer was fabricated. Under visible-LED-light irradiation, removal of refractory analgesic carbamazepine (CBZ) and total organic carbon (TOC) reached 100% and 67.41%, respectively, by Fe 3 O 4 /BiOBr@HC20% within 40 min, demonstrating the excellent photocatalytic activity compared to other photocatalysts. The narrower band gap (2.02 eV) of Fe 3 O 4 /BiOBr@HC obviously improved the visible light absorption. The hydrochar with abundant surface oxygen functional groups provided more active oxygen species ·O 2 – (4.05 µM) and ·OH (107.8 nM), and acted as an electron bridge to promote the electron transfer of BiOBr and Fe 3 O 4 . Eleven main CBZ intermediates were identified and three degradation pathways were proposed to illustrate the contribution of superoxide radicals, hydroxyl radicals, and photogenerated holes to the photodegradation of CBZ. Furthermore, five-cycle reusing experiments revealed that Fe 3 O 4 /BiOBr@HC composite catalysts have excellent reusability and stability, indicating that they have a promising application future.