Carbon-based Composite Materials Research Articles

Low-temperature subcritical water dechlorination composites of waste PVC/coal fly ash with powerful sensing activity for chemiluminescent detection of acetamiprid and imidacloprid

Pesticide residues in agricultural products are serious threat to people's health. Real-time monitoring of pesticides residues in the environment and agricultural products posed challenges to sustainable methods with high analytical performance for pesticide detection. Herein, waste PVC/coal fly ash (the mass ratio of PVC and coal fly ash was 4:1) was dechlorinated in subcritical water at low temperature to achieve nearly 100 % dechlorination of PVC and obtain carbon-based composite materials (CM-Fe/Al/Si-dPVC) with strong sening activity. For CM-Fe/Al/Si-dPVC, CFe bonding resulted in strong electron migration, and nano/μm SiO2 and Al2O3 doping in the layered polyene C matrix provided large specific surface area, and silicon hydroxyl created good heterogeneous catalytic interfaces. CM-Fe/Al/Si-dPVC could strongly trigger luminol chemiluminescence (CL) reaction and produce intense CL signals. Neonicotinoid pesticides (acetamiprid and imidacloprid) bonded with CM-Fe/Al/Si-dPVC through coordination chelation and hydrogen bonding, which shielded the catalytic active site and increased the Fermi level of system, thus quenching CL reaction. Inspired by these, a cheap CL assay was constructed for detecting neonicotinoids combinations of acetamiprid and imidacloprid (NICs). The detection limits of NICs were 0.7 ng/L. Satisfactory recoveries were obtained for real agricultural products and environmental samples. The results of life cycle evaluation (LCA) revealed that the strategy had significantly small global warming potential (GWP). This work presented a sustainable method with environmental benefits for the detection of neonicotinoids, and also opened up new way for the recycling of organic solid wastes.

In situ loading of ZnO on hierarchical porous carbon derived from banana-peel waste to enrich mechanism for microwave absorption

Biomass has received widespread attention due to its easy availability, low cost, and environmental friendliness as an electromagnetic wave absorber candidate. Inspired by the natural porosity of biomass, the three-dimensional (3D) porous carbon materials derived from banana peels were prepared via coordination and pyrolysis carbonization. A conductive network of biomass-zinc complexes was constructed by introducing Zn2+ to coordinate with organic polymers. Hierarchical porous carbon/ZnO composites with a 3D skeleton network were obtained, which demonstrated outstanding electromagnetic wave absorption performance with an effective absorption bandwidth (EAB) of 6.72GHz and the reflection loss (RL) of -44.18dB. The banana peel-derived porous carbon (BPC) embedded with ZnO particles brings about conductive loss and interface polarization, further enriching the microwave loss mechanisms. This work offers a fresh idea for creating a green, sustainable, and high-value functional carbon-based composite material.

Perovskite Nanowire-Based Electrochemical Sensing for Selective and Rapid Detection of Hydrogen Peroxide

Nanowires possess inherent advantages in improving the reduction of boundary stacking defects and enhancing charge transfer or migration. Here, we synthesized all-inorganic perovskite nanowires CsPbBr3 (PVSK NW) and obtained CsPb1-xSnxBr3 (PVSK-Sn NW) and CsPb1-xGexBr3 (PVSK-Ge NW) nanowires through doping with different elements (Sn and Ge). Elemental doping endows the nanowires with unique narrow fluorescence spectra, high optical absorption coefficients, tunable optical bandgaps, and high carrier mobility. Introducing different perovskite nanowires into carbon-based composite materials (super p/Nafion) can overcome the challenges of hydrogen peroxide (H2O2) detection sensitivity and matrix interference. H2O2 in PBS (phosphate buffered saline) solution (pH 7.0) was detected by current analysis i-t curve mode. The results demonstrate that the addition of perovskite nanowires exhibits a high level of detection sensitivity for H2O2 electrochemical reduction. Particularly, the linear concentration range detected by PVSK-Sn NW is 1-6000µM, with a detection limit of 0.12µM. Even in the presence of interfering molecules (ascorbic acid, uric acid, glucose), the detection of H2O2 maintains high sensitivity and selectivity. This study overcomes the limitations of perovskite materials in water-based detection, enhancing their future commercial applications as sensing devices.

Structural optimization and electrocatalytic hydrogen production performance of carbon-based composites: A mini-review

The energy demand has increased significantly in recent years and it is urgent to develop a renewable energy system that is highly efficient and non-noble metal-based. Hydrogen energy is an environmentally friendly energy source with abundant resources, which can be used to solve the problem of high energy demand without greenhouse gas emissions. However, the development of catalysts for hydrogen production technology by electrolysis of water is slow, mainly due to the complexity of the electrolysis hydrogen generation process, low hydrogen production efficiency, weak electrode material activity and high cost. Among the non-noble metal-based catalysts, carbon-based materials have high conductivity, tunable chemical bonding, and easily modified morphology, making them beneficial to achieving efficient hydrogen production, though pure carbon composites suffer from few surface-active sites and unmoderated hydrogen bonding energy, which need to be further optimized. The principle of electrocatalytic hydrogen production from the perspectives of reaction thermodynamics and kinetics is analyzed and discussed in this paper. Thermodynamics of electrocatalytic hydrogen production is reflected by the Gibbs free energy of hydrogen adsorption (ΔGH*) and electrode potential (E). Reaction kinetics of the electrocatalytic hydrogen production process are reflected by overpotential, Tafel slope and exchange current density. Structural optimization methods of carbon-based composite materials and hydrogen production performance after structural optimization are also summarized. Structural optimization methods of carbon-based composite materials mainly include introducing active sites, improving conductivity, increasing specific surface area and introducing self-supporting materials. Finally, prospects are proposed for the development direction and existing problems of electrocatalytic hydrogen production performance of carbon-based composites.

Porous carbon network-based composite phase change materials with heat storage capacity and thermal management functions

Porous carbon network-based phase change composites have been widely used in energy storage and thermal management related fields. At present, the demand of energy crisis for photothermal energy storage and the prevention and management of thermal abuse of electronic equipment constantly promote the development of carbon-based composite phase change materials (PCMs). Therefore, a series of new composite materials filled with PCMs and polyethylene glycol (PEG) and added with flame-retardant magnesium hydroxide were developed, which makes the composites show certain flame-retardant ability in high-temperature environments. The results show that the thermal conductivity increases from 0.25 to 0.94 W/m·K, and the latent heat of phase change remains at 142.7 J/g. In addition, due to the capillary effect caused by the synergistic effect of multi-pore carbon (MPC) structure and cellulose macromolecular chain, the composite material has good shape stability, which effectively prevents the leakage behavior of PCMs during solid-liquid phase change. Moreover, the absorbance of the composite material can reach 1.28 L/(g cm) in the ultraviolet–visible light range of 200 nm–800 nm, and its photothermal conversion efficiency can reach 90.8 %. Therefore, this material has a broad application prospect in the thermal management of electronic equipment and photothermal energy storage devices.

Carbon composites as an Avante garde material in mitigating dyes and heavy metal pollution

Abstract Depletion of potable water availability is threatening the whole biota, owing to the presence of anthropogenic compounds and hazardous chemicals above the permissible levels. Although many conventional methods exist, the development of innovative technologies is critical for wastewater treatment and recycling. Carbon composites have recently seen widespread use across a variety of industries due to their distinctive and superior properties. These carbon composites are easily integrated into many stages of the treatment process, making them efficient, cost-effective, and environmentally friendly. This chapter discusses the importance and effectiveness of carbon-based composite materials in removing toxic dyes and heavy metal contaminants from the environment. Carbon composites are classified according to their sources, preparation methods, and applications. This chapter also discusses various research perspectives on carbon composites, particularly from an environmental and financial standpoint.

Combustion-Assisted construction of Defect-Enriched hierarchical carbon composites towards efficient Low-Frequency electromagnetic wave absorption

Due to the high intrinsic conductivity of graphitized carbon-based composite materials, it induces a serious skin effect of incident electromagnetic waves, which deteriorates impedance matching and limits the wave absorption performance in the low-frequency regions. The introduction of defects can change the electrical and physical and chemical properties of carbon-based materials, affect the density of skin current, and thereby improve the overall performance of carbon-based absorbers. Therefore, it is important to develop a simple, low-cost, and fast preparation method for defect-rich structures. Herein, the defect-enriched hierarchical composites have been synthesized successfully via the soaking-burning-annealing process. The combustion treatment introduced numerous defects and oxygen vacancies while inducing a non-graphitization transition that reduced conductivity and improved electromagnetic balance in the low-frequency region. As expected, the charred sample exhibited notable enhancements in reflection loss (RL) and the effective absorption bandwidth within the low-frequency range of 2–8 GHz. The value of RL reached −52.2 dB, marking a 199 % increase over the unburned sample, while the effective absorption bandwidth increased by 28 % to 2.70 GHz. Even at a filling rate of only 10 %, the RLmin values of the optimal sample were lower than −30 dB across the S, C, X, and Ku bands. Additionally, the combination-induced defects led to phonon scattering, thereby reducing the thermal conductivity of the material. Thus, combustion can enhance the low-frequency microwave properties and thermal insulation of carbon-layered composites.

Current On-Skin Flexible Sensors, Materials, Manufacturing Approaches, and Study Trends for Health Monitoring: A Review.

Due to an ever-increasing amount of the population focusing more on their personal health, thanks to rising living standards, there is a pressing need to improve personal healthcare devices. These devices presently require laborious, time-consuming, and convoluted procedures that heavily rely on cumbersome equipment, causing discomfort and pain for the patients during invasive methods such as sample-gathering, blood sampling, and other traditional benchtop techniques. The solution lies in the development of new flexible sensors with temperature, humidity, strain, pressure, and sweat detection and monitoring capabilities, mimicking some of the sensory capabilities of the skin. In this review, a comprehensive presentation of the themes regarding flexible sensors, chosen materials, manufacturing processes, and trends was made. It was concluded that carbon-based composite materials, along with graphene and its derivates, have garnered significant interest due to their electromechanical stability, extraordinary electrical conductivity, high specific surface area, variety, and relatively low cost.

The Microstructure and Thermal Conductive Behavior of Three-Dimensional Carbon/Carbon Composites with Ultrahigh Thermal Conductivity.

Carbon-based composite materials, denoted as C/C composites and possessing high thermal conductivity, were synthesized utilizing a three-dimensional (3D) preform methodology. This involved the orthogonal weaving of mesophase pitch-based fibers in an X (Y) direction derived from low-temperature carbonization, and commercial PAN-based carbon fibers in a Z direction. The 3D preforms were saturated with mesophase pitch in their raw state through a hot-pressing process, which was executed under relatively low pressure at a predetermined temperature. Further densification was achieved by successive stages of mesophase pitch impregnation (MPI), followed by impregnation with coal pitch under high pressure (IPI). The microstructure and thermal conductivity of the C/C composites were systematically examined using a suite of analytical techniques, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and PLM, amongst others. The findings suggest that the volumetric fraction of fibers and the directional alignment of the mesophase pitch molecules can be enhanced via hot pressing. The high graphitization degree of the mesophase pitch matrix results in an increased microcrystalline size and thus improved thermal conductivity of the C/C composite. Conversely, the orientation of the medium-temperature coal pitch matrix is relatively low, which compensates for the structural inadequacies of the composite material, albeit contributing minimally to the thermal conductivity of the resultant C/C composites. Following several stages of impregnation with mesophase pitch and subsequent impregnation with medium-temperature coal pitch, the 3D C/C composites yielded a density of 1.83 and 2.02 g/cm3. The thermal conductivity in the X (Y) direction was found to be 358 and 400 W/(m·K), respectively.

Solution-Plasma Synthesis and Characterization of Transition Metals and N-Containing Carbon-Carbon Nanotube Composites.

Lithium-air batteries (LABs) have a theoretically high energy density. However, LABs have some issues, such as low energy efficiency, short life cycle, and high overpotential in charge-discharge cycles. To solve these issues electrocatalytic materials were developed for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which significantly affect battery performance. In this study, we aimed to synthesize electrocatalytic N-doped carbon-based composite materials with solution plasma (SP) using Co or Ni as electrodes from organic solvents containing cup-stacked carbon nanotubes (CSCNTs), iron (II) phthalocyanine (FePc), and N-nethyl-2-pyrrolidinone (NMP). The synthesized N-doped carbon-based composite materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). TEM observation and XPS measurements revealed that the synthesized carbon materials contained elemental N, Fe, and electrode-derived Co or Ni, leading to the successful synthesis of N-doped carbon-based composite materials. The electrocatalytic activity for ORR of the synthesized carbon-based composite materials was also evaluated using electrochemical measurements. The electrochemical measurements demonstrated that the electrocatalytic performance for ORR of N-doped carbon-based composite material including Fe and Co showed superiority to that of N-doped carbon-based composite material including Fe and Ni. The difference in the electrocatalytic performance for ORR is discussed regarding the difference in the specific surface area and the presence ratio of chemical bonding species.

Manganese dioxide (MnO2) and biomass-derived carbon-based electroactive composite materials for supercapacitor applications

This review highlights the importance of MnO2 & biomass-derived carbon materials and composites made from them for energy storage applications.

Green-engineered clay- and carbon-based composite materials for the adsorption of benzene from air

Benzene is a carcinogenic volatile organic compound (VOC) that is ubiquitously detected in enclosed spaces due to emissions from cooking activities, building materials, and cleaning products. To remove benzene and other VOCs from indoor air and protect public health, traditional fabric filters have been modified to contain activated carbons to enhance the filtration efficacy. In this study, composites derived from natural clay minerals and activated carbon were individually green-engineered with chlorophylls and were attached to the surface of filter materials. These systems were assessed for their adsorption of benzene from air using in vitro and in silico methods. Isothermal, thermodynamic, and kinetic experiments indicated that all green-engineered composites had improved binding profiles for benzene, as demonstrated by increased binding affinities (Kf ≥ 900 vs 472) and lower values of Gibbs free energy (ΔG = −16.8 vs −15.2) compared to activated carbon. Adsorption of benzene to all composites was achieved quickly (< 30 min), and the green-engineered composites also showed low levels of desorption (≤ 25%). While free chlorophyll is known to be photosensitive, chlorophylls in the green-engineered composites showed photostability and maintained high binding rates (≥ 70%). Additionally, the in silico simulations demonstrated the significant contribution of chlorophyll for the overall binding of benzene in clay systems and that chlorophyll could contribute to benzene binding in the carbon-based systems. Together, these studies indicated that novel, green-engineered composite materials can be effective filter sorbents to enhance the removal of benzene from air.

Antibacterial properties of metal nanoparticles–incorporated activated carbon composites produced from waste biomass precursor

Activated carbon-based composite materials, together with the well known antibacterial activity of metal nanoparticles, urged the performance of this study to prepare new antibacterial materials with antimicrobial activity, as an important step in fighting pathogenic organisms. Activated carbon derived from a waste source - almond shells - were combined with metal (Ag, Cu, Mg) nanoparticles, in order to obtain metal composite with desirable characteristics. The composites were obtained using one-step high-temperature hydro-pyrolysis and further impregnation of the metal from water solution. Investigation of the structure, chemical composition and morphology of obtained composites was carried out by scanning electron microscopy, XRD, XPS, elemental and BET analysis, before testing their antimicrobial activity. Strongest antibacterial effect against E. coli was observed when 10 % Cu Activated Carbon Composite (ACCCu) was used attaining 100 % reduction of microbial count even at the starting point. ACCAg, ACCMg and activated carbon only, demonstrated such effect after 24 h. Best results after treatment of S. aureus were achieved with ACCAg and ACCCu after 24 h.The results indicate that the antibacterial activity depends on the contact time, bacterial species, nature of the metal and metal concentration. The novel metal nanoparticles-incorporated activated carbon composites demonstrated very good antibacterial activity. The investigation provides novel materials with antibacterial properties for further development and potential application in hygiene devices.

Advanced 3D-architected carbon-based photothermoelectric energy harvesters for self-powered and responsive magnetic and UV sensing

Towards solving the technical challenges of self-powering wireless sensor networks (WSNs), feasibility studies of high-efficiency energy harvesters are expected to be break-through technologies. Herein, we propose a closed-loop self-powering system, for which we design a novel 3D-architecture carbon-based photothermoelectric organic composite phase-changing material (PCM) energy harvester for self-powered and responsive magnetic and UV sensing by infusing with Fe3O4 nanoparticles and tetradecanol as PCM. The closed-loop system possesses excellent energy storage, conversion efficiency up to 89.83 % as well as photothermoelectric conversion capacity with maximum output voltage and current of 196.6 mV and 8.64 mA, respectively. More importantly, the voltage provided by the phase-change-based photothermoelectricity enables it to be used as a microcapacitor with a specific capacitance of 31.05 F/g at 0.01 A/g. Moreover, it is responds to magnetic field and UV radiation with high sensitivity, the average response time being 1 s. This potential breakthrough composite paves way for use in a variety of high-energy self-powered agile sensing WSNs applications.

Boosting of electromagnetic wave absorption properties by multiple reinforcement mechanisms of metals in FeNi3/MoS2@NSAPC composites

The prominence of electromagnetic wave pollution problems in military construction and people development has promoted extensive research on electromagnetic wave-absorbing materials. In this paper, a multi-metal-loaded N, S co-doped carbon-based composite wave-absorbing material has been prepared and converted into FeNi3/MoS2@NSAPC through heat treatment on this basis. FeNi3 and MoS2 construct a multiple loss mechanism to enhance the N, S double-doped carbon-based wave-absorbing material, which demonstrates by the effective absorption. The EAB of FeNi3/MoS2@NSAPC is broadened, and the RLmin is improved. The results show that a RLmin = -60.66 dB obtains at a sample thickness of 1.4 mm, an absorber doping of 15 wt%, and an EAB of 5.19 GHz. This work explains the enhancement effect of metal in the “metal/heteroatom/carbon” composite system. It provides a basis for the study of Ni- or Mo-doped carbon-based wave-absorbing materials.

Coupling Carbon-Based Composite Phase Change Materials with a Polyurethane Sponge for Sustained and Efficient Solar-Driven Cleanup of Viscous Crude Oil Spill.

The efficient cleanup of crude oil spills is a worldwide problem due to their high viscosity and low fluidity. Under the assistance of solar radiation, adsorbents with in situ heating function are becoming the ideal candidates to solve this problem. In this study, a new strategy coupling a polyurethane (PU) sponge with phase change materials (PCMs) is proposed to realize the efficient utilization of solar energy and crude oil cleanup. Wormlike carbon nanotubes/mesoporous carbon (CNTs/MC) with a core-shell structure was used to encapsulate polyethylene glycol (PEG), which was then introduced into the PU sponge for photothermal conversion and thermal storage. After coating with a polydimethylsiloxane (PDMS) layer, the sponge was further endowed with hydrophobic characteristics. Additionally, PDMS can function as a binder between PEG@CNTs/MC and sponge skeleton. The resulting PEG@CNTs/MC/PU/PDMS (named as PEG@CMPP) exhibited excellent photothermal conversion and high absorption capacity for high-viscosity crude oil. Most importantly, thanks to the heat storage properties of PEG, the stored heat can be sustainably transferred to the surrounding crude oil to promote its continuous absorption even under insufficient light intensity conditions. The crude oil absorption capacity of PEG@CMPP-3 reached approximately 0.96 g/cm3 even after the light source was removed, which manifested the distinctive advantages compared to the conventional photothermal adsorbent. The proposed approach integrates the high efficiency of solar-assisted heating and energy-conserving advantage, thereby providing a feasible strategy for highly efficient remediation of viscous crude oil spills.

Carbon-based EM functional materials and multi-band microwave devices: Current progress and perspectives

Owing to their low electromagnetic pollution, high flexibility, tunability, and environmentally friendly properties, carbon-based EM functional materials are considered to be potential candidates for the designs of next-generation microwave devices. The purpose of this review is to survey and systematize the growing body of literature on carbon-based microwave devices and to help establish better guidelines for future research and development on the subject. So far, research on the application of carbon-based functional materials in microwave device design has been actively carried out. At present, the carbon materials widely used in electronic devices mainly include graphene, carbon nanotubes (CNTs), and MXene. Here, we systematically review the applications of different carbon-based functional materials in metamaterial absorbers, metasurfaces, antennas, and flexible sensors, and also introduce the application of carbon-based composite functional materials. Microwave devices based on the above materials show great promise in areas such as 6G, wireless body area networks, and wearable health monitoring devices. Although microwave devices designed based on some carbon-based functional materials are currently only in the ideal simulation stage, as the production system of new materials matures, it can be assumed that more opportunities for the development of the next generation of microwave devices will be provided. Last but not least, the development of carbon-based EM functional materials in multi-band microwave devices is summarized, and the new tendency is prospected.

Shape-Memory-Alloys Enabled Actuatable Fiber Sensors via the Preform-to-Fiber Fabrication

Integrative actuators and sensors within a single active device offer compelling capabilities in developing robotics, prosthetic limbs, and minimally invasive surgical tools. However, instrumenting smart and active devices with miniaturized sizes for easy customizability and high yield is largely restricted by the current manufacturing technologies. Here, we report the development of flexible polymer-based actuatable fiber sensors, produced by the preform-to-fiber thermal drawing process. It has both mechanical actuation realized by the incorporated shape-memory alloy (SMA) wires and biochemical sensing provided by carbon-based composite materials. The tip of such a fiber could be actuated with a high spatiotemporal resolution by the shape-memory effect. And, its integrated carbon composite exhibits intrinsically high sensitivity toward electroactive molecules. Here, we showed it can selectively detect adrenaline as low as 100 nM with the coexistence of major interferent molecules. We succeeded in using such an actuatable fiber sensor to target the bifurcated vessel model and capture the localized adrenaline information. The actuatable fiber sensor technologies developed here can greatly push the technological advancement in the soft and flexible robotic fields to include additional functions on top of their pure mechanical behaviors and open possibilities for achieving closed-loop control for high-precision operations.

Deep eutectic solvent-assisted fabrication of bioinspired 3D carbon-calcium phosphate scaffolds for bone tissue engineering.

Tissue engineering is a burgeoning field focused on repairing damaged tissues through the combination of bodily cells with highly porous scaffold biomaterials, which serve as templates for tissue regeneration, thus facilitating the growth of new tissue. Carbon materials, constituting an emerging class of superior materials, are currently experiencing remarkable scientific and technological advancements. Consequently, the development of novel 3D carbon-based composite materials has become significant for biomedicine. There is an urgent need for the development of hybrids that will combine the unique bioactivity of ceramics with the performance of carbonaceous materials. Considering these requirements, herein, we propose a straightforward method of producing a 3D carbon-based scaffold that resembles the structural features of spongin, even on the nanometric level of their hierarchical organization. The modification of spongin with calcium phosphate was achieved in a deep eutectic solvent (choline chloride : urea, 1 : 2). The holistic characterization of the scaffolds confirms their remarkable structural features (i.e., porosity, connectivity), along with the biocompatibility of α-tricalcium phosphate (α-TCP), rendering them a promising candidate for stem cell-based tissue-engineering. Culturing human bone marrow mesenchymal stem cells (hMSC) on the surface of the biomimetic scaffold further verifies its growth-facilitating properties, promoting the differentiation of these cells in the osteogenesis direction. ALP activity was significantly higher in osteogenic medium compared to proliferation, indicating the differentiation of hMSC towards osteoblasts. However, no significant difference between C and C-αTCP in the same medium type was observed.

An Insight into Carbon Nanomaterial-Based Photocatalytic Water Splitting for Green Hydrogen Production

At present, the energy shortage and environmental pollution are the burning global issues. For centuries, fossil fuels have been used to meet worldwide energy demand. However, thousands of tons of greenhouse gases are released into the atmosphere when fossil fuels are burned, contributing to global warming. Therefore, green energy must replace fossil fuels, and hydrogen is a prime choice. Photocatalytic water splitting (PWS) under solar irradiation could address energy and environmental problems. In the past decade, solar photocatalysts have been used to manufacture sustainable fuels. Scientists are working to synthesize a reliable, affordable, and light-efficient photocatalyst. Developing efficient photocatalysts for water redox reactions in suspension is a key to solar energy conversion. Semiconductor nanoparticles can be used as photocatalysts to accelerate redox reactions to generate chemical fuel or electricity. Carbon materials are substantial photocatalysts for total WS under solar irradiation due to their high activity, high stability, low cost, easy production, and structural diversity. Carbon-based materials such as graphene, graphene oxide, graphitic carbon nitride, fullerenes, carbon nanotubes, and carbon quantum dots can be used as semiconductors, photosensitizers, cocatalysts, and support materials. This review comprehensively explains how carbon-based composite materials function as photocatalytic semiconductors for hydrogen production, the water-splitting mechanism, and the chemistry of redox reactions. Also, how heteroatom doping, defects and surface functionalities, etc., can influence the efficiency of carbon photocatalysts in H2 production. The challenges faced in the PWS process and future prospects are briefly discussed.