3N4 Composite Photocatalysts Research Articles

Microwave-assisted synthesis of ZnIn2S4/g-C3N4 heterojunction photocatalysts for efficient visible light photocatalytic hydrogen evolution

A series of ZnIn2S4/g-C3N4 composite photocatalysts for photosplitting water into H2 have been prepared by a microwave-assisted method for the first time. The pH medium in the preparation of the photocatalysts is found to have a strong influence on the photocatalytic activity of ZnIn2S4/g-C3N4, and 387μmol/h of H2 evolution rate is achieved for ZnIn2S4/20wt% g-C3N4 obtained in the neutral medium. Furthermore, the 〈100〉 crystal facet is revealed to be essential for the ZnIn2S4/g-C3N4 heterojunction formation. A preliminary mechanism is suggested that this heterojunction is beneficial for the interfacial photogenerated carrier separation and transfer, thus leading to better photocatalytic activity.

Efficient water disinfection with Ag2WO4-doped mesoporous g-C3N4 under visible light

Ag2WO4/g-C3N4 composite photocatalyst was synthesized by polymerization of thiourea and ammonia chloride combined with the deposition-precipitation method, which was applied as an efficient visible-light driven photocatalyst for inactivating Escherichia coli (E. coli). The physicochemical properties of these photocatalysts were systematically characterized by various techniques such as SEM, TEM, XRD, FT-IR, BET, UV–vis DRS and PL. The synthesized photocatalysts exhibited outstandingly enhanced photocatalytic disinfection efficiency compared with that of pure g-C3N4 and Ag2WO4 under visible light. Furthermore, the optimal mass ratio of the Ag2WO4 to g-C3N4 was 5wt%, and a number of live bacteria could be completely inactivated with Ag2WO4(5%)/g-C3N4 (100μg/mL) after 90min under visible light irradiation. The high disinfection efficiency is due to the synergetic effect between g-C3N4 and Ag2WO4, including a good distribution of Ag2WO4 particles on the surface of g-C3N4 and an improved separation rate of photogenerated electron-hole pairs. The enhanced disinfection mechanism was also investigated using photogenerated current densities and electrochemical impedance spectroscopy (EIS). Considering the bulk availability and excellent disinfection activity of Ag2WO4/g-C3N4 composite, it is a promising solar-driven photocatalyst for cleaning the microbial contaminated water.

Enhanced photocatalytic activity of TiO2 nanoparticles using WS2/g-C3N4 hybrid as co-catalyst

TiO2/WS2/g-C3N4 composite photocatalysts were synthesized by a liquid-exfoliation-solvothermal method. In this process, the WS2/g-C3N4 nano-sheets were prepared by liquid-exfoliation method from the bulk WS2 and C3N4 in the alcohol system, and then the TiO2 nanoparticles (NPs) grew on the WS2/g-C3N4 nano-sheets by in-situ synthesized technique. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic degradation of methyl orange (MO). The results showed that the as-prepared samples exhibited higher photocatalytic activities as compared to the pure TiO2, g-C3N4 and TiO2/g-C3N4 composite. The enhanced photocatalytic activities of TiO2/WS2/g-C3N4 photocatalysts could be attributed to the synergistic effect of heterostructure between TiO2 NPs and WS2/g-C3N4 nano-sheets, which could efficiently improve the separation of photogenerated electron/hole pairs and utilization efficiency of photons. The quenching tests of radicals indicated that ·O−2 had crucial effect on degradation of MO, which demonstrated that ·O−2 was the main active radical in photocatalytic reaction process.

Synthesis and characterization of novel Ag2CO3/g-C3N4 composite photocatalysts with excellent solar photocatalytic activity and mechanism insight

The photocatalytic performance of g-C3N4 is greatly limits by its inherent drawbacks, thus it is urgent to boost the photocatalytic activity of g-C3N4. Constructing Z-scheme composite photocatalysts has received great interesting in the photocatalysis field because of its great potential to promote the catalytic activity of photocatalysts by accelerating the separation of the photo-induced charge pairs. In this study, a series of Z-scheme Ag2CO3/g-C3N4composites were fabricated and characterized by X-ray diffraction patterns (XRD), inductively coupled plasma (ICP) spectroscopy, particle size analyzer, UV–vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), surface photovoltage spectroscopy (SPS),electron spin-resonance (ESR) spectroscopy and scavenger experiments. The corresponding photocatalytic performance toward methyl orange (MO) decolorization were investigated under the simulated sunlight irradiation. The results reveal that the Ag2CO3/g-C3N4composites display higher photocatalytic activity than the bare g-C3N4. The photocatalytic activity of the 7% molar ratio of Ag/g-C3N4 composite is more than 15 times of that of the bare g-C3N4. Based on the results of ESR and SPS, a Z-scheme separation and transfer scheme of the photo-induced charge pairs of Ag2CO3/g-C3N4 was proposed. This study sheds light on understanding the Z-scheme charge transfer mechanism.

In-situ fabrication of CuS/g-C3N4 nanocomposites with enhanced photocatalytic H2-production activity via photoinduced interfacial charge transfer

In this work, novel CuS/g-C3N4 composite photocatalysts were successfully prepared via a simple in-situ growth method. CuS nanoparticles, with an average diameter of ca.10 nm, were well dispersed on the surface of g-C3N4, revealing that g-C3N4 nanosheets were promising support for in-situ growth of nanosize materials. The CuS/g-C3N4 composites exhibited highly enhanced visible light photocatalytic H2 evolution from water-splitting compared to pure g-C3N4. The optimum photocatalytic activity of 2 wt% CuS/g-C3N4 composite photocatalytic H2 evolution was about 13.76 times higher than pure g-C3N4. The enhanced photocatalytic activity is attributed to the interfacial charge transfer (IFCT). In this system, electrons in the valence band (VB) of g-C3N4 can transfer directly to CuS clusters, causing the reduction of partial CuS to Cu2S, which can act as an electron sink and co-catalyst to promote the separation and transfer of photo-generated electrons. The accumulated photoinduced electrons in CuS/Cu2S clusters could effectively reduce H+ to produce H2. This work provides a possibility for constructing low-cost CuS as a substitute for noble metals in the photocatalytic production of H2 via a facile method based on g-C3N4.

C60/graphene/g-C3N4 composite photocatalyst and mutually- reinforcing synergy to improve hydrogen production in splitting water under visible light radiation

g-C3N4 as a new metal-free photocatalytic material for water splitting has attracted much attention in recent years, but its photocatalytic efficiency needs further improvement. Here we synthesized novel C60/graphene/g-C3N4 composite photocatalytic materials with high hydrogen generation ability for water splitting under visible light radiation (λ>420nm). These materials take full advantage of the electron conduction expressing of graphene and the superior-strong electron-attracting ability of C60. The mutually-reinforcing synergy between graphene and C60 improves the migration and utilization efficiency of photo-generated electrons and accelerates the separation of photo-generated charges, thus significantly enhancing the hydrogen generation capacity of g-C3N4. The hydrogen production amount and rate of C60/graphene/g-C3N4 (10mg/L C60 and graphene) after 10h are 5449.5µmol/g and 545µmol/g/h, which is 539.6 times of pure g-C3N4 under the same condition. The values are 50.8 and 4.24 times of graphene/g-C3N4 (10mg/L graphene) and C60/g-C3N4 (10mg/L C60), respectively. The apparent quantum yield of C60/graphene/g-C3N4 (10mg/L C60 and graphene) in 97h is about 7.2%. The improvement of hydrogen generation activity in 97h suggests the high long-time stability of C60/graphene/g-C3N4 in photocatalytic water spitting. The photocatalytic ability of C60/graphene/g-C3N4 can be controlled by regulating the addition of graphene and C60. The mutually-reinforcing synergy between graphene and C60 was proved by X-ray photoelectron spectroscopy, photoluminescence spectrum and organic electron acceptors of MV2+. Thus, the joint action of C60 and graphene promotes the migration, separation and utilization of photo-generated electrons, which is responsible for the significant enhancement of photocatalytic performance.

Precipitation dispersion of various ratios of BiOI/BiOCl nanocomposite over g-C 3 N 4 for promoted visible light nanophotocatalyst used in removal of acid orange 7 from water

Abstract BiOI-BiOCl/g-C3N4 composite photocatalysts with different weight percentages of BiOI and BiOCl were synthesized by a facile precipitation method at room temperature. The synthesized composites were well characterized by XRD, EDX, FTIR, TEM, BET, FESEM and UV–vis DRS techniques. The results indicated that the successful combination of three components greatly enhanced visible light absorption. Among prepared samples, the BiOI(50)-BiOCl(30)/C3N4(20) composite exhibited superior photocatalytic activity for degradation of acid orange 7 under visible light irradiation. The degradation efficiency was found to be 97.4% for this composite. Also, surface ionization behaviour of photocatalyst was investigated and the pHPZC of the BiOI(50)-BiOCl(30)/C3N4(20) was found to be 6. The increased photocatalytic activity of this composite is mainly attributed to the efficient separation and transfer of photogenerated electron-hole pairs originating from the formation of multi-heterojunction structure between BiOCl, BiOI and g-C3N4. To find the optimum condition for photocatalysis, the effects of pH, photocatalyst loading, initial concentration of the model contaminant were investigated. Also, photostability of BiOI(50)-BiOCl(30)/C3N4(20) was examined and possible photocatalytic mechanism for degradation of acid orange 7 was proposed.

Fabrication of novel visible-light-driven AgI/g-C3N4 composites with enhanced visible-light photocatalytic activity for diclofenac degradation

A visible-light-driven heterostructured AgI/g-C3N4 was prepared by a deposition-precipitation method. The composition, structure, morphology, and optical properties of the photocatalyst were characterized by Brunauer-Emmett-Teller method (BET), X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), scanning electron microscope (SEM), UV–vis diffused reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), photocurrent, and electrochemical impedance spectroscopy (EIS), respectively. AgI/g-C3N4 composite photocatalysts exhibited higher photocatalytic activities than those of AgI nanoparticles and g-C3N4 in the degradation of diclofenac (a model anti-inflammatory medicine) under visible light irradiation (λ≥400nm). When the mass molar ratio of AgI was 45% in AgI/g-C3N4, the reaction rate constant of diclofenac degradation reached 0.561min−1, which was almost 12.5 and 43.2 times higher than that achieved by AgI (0.045min−1) and g-C3N4 (0.013min−1). The h+ and O2- were pinpointed as the main reactive species in the photocatalytic reaction using their obligate radical scavengers. Diclofenac was completely degraded and partly mineralized during the photodegradation. The main intermediates were determined by liquid chromatograph mass spectrometer (LC-MS), and toxicological assessments were carried out to evaluate the change of toxicity in the degradation process. In addition, the photocatalysts showed excellent stability over multiple reaction cycles. Finally, a possible photocatalytic and charge separation mechanism was proposed.

Novel visible-light-driven Z-scheme Bi12GeO20/g-C3N4 photocatalyst: Oxygen-induced pathway of organic pollutants degradation and proton assisted electron transfer mechanism of Cr(VI) reduction

We successfully synthesized novel solid state Z-scheme visible-light-driven Bi12GeO20/g-C3N4 composite photocatalysts and investigated their photocatalytic activities for degradation of microcystin-LR and RhB, and for reduction of aqueous Cr(VI). The TEM and HRTEM images clearly showed the heterogeneous nanostructures at the interface between Bi12GeO20 and g-C3N4. The as-prepared Bi12GeO20/g-C3N4 composites exhibited enhanced photocatalytic activities for the degradation of microcystin-LR and RhB aqueous solution and reduction of aqueous Cr(VI) as compared to the pure Bi12GeO20 and g-C3N4 under visible-light irradiation. On the basis of the radical species trapping experiments and ESR analyses, O2− and h+ were confirmed to be the mainly active species involved in the degradation of organic pollutants and this reaction was identified to be an oxygen-induced pathway. Meanwhile, combined with the in situ ATR-FTIR spectroscopy and kinetic isotope effect investigations, the photocatalytic reduction of aqueous Cr(VI) was identified as a proton assisted electron transfer reaction. Moreover, the enhanced photocatalytic activities of the Bi12GeO20/g-C3N4 composites can be attributed to the improved photo-absorption properties and effective separation of photo-induced charge carriers caused by the Z-scheme system of the as-prepared Bi12GeO20/g-C3N4 composites.

Enhanced efficiency and stability of Co0.5Cd0.5S/g-C3N4 composite photo-catalysts for hydrogen evolution from water under visible light irradiation

A simple hydrothermal process was developed to synthesize Co0.5Cd0.5S/g-C3N4 composite photocatalysts. The crystal structure and surface morphology were characterized with XRD and TEM. The chemical state on the material surface, the chemical structure as well as the ultraviolet–visible light response of the photocatalyst were investigated with XPS and UV–vis DRS. The hydrogen production experiments indicated that the Co0.5Cd0.5S catalyst exhibits enhanced efficiency and stability with the addition of g-C3N4, which effectively inhibited the occurrence of photo-corrosion and promoted the separation efficiency of the photogenerated electron–hole pairs. The highest rate of H2 generation from the composite catalyst is up to 6.31 mmol g−1 h−1 under visible light (λ > 400 nm).

Highly efficient visible-light photocatalytic performance based on novel AgI/g-C3N4 composite photocatalysts

A novel AgI/g-C3N4 composite photocatalysts with enhanced visible-light photocatalytic pollutants degradation activity were synthesized by a facile ultrasonication-precipitation method. The composite photocatalysts were characterized by XRD, FESEM, FTIR, XPS, DRS and basic test. The results proved that the AgI/g-C3N4 composite photocatalysts exhibit excellent photocatalytic performance and favorable stability towards Methylene blue (MB) degradation in aqueous solution under visible light (λ>420nm). Approximately 97.5% of MB was degraded after 1h of irradiation using the best catalyst. Superior stability was also achieved in the cyclic runs, indicating that the as-prepared composite photocatalyst has potential application for treatment of organic-dye-contaminated wastewaters.

In situ hydrothermal synthesis and enhanced photocatalytic H2-evolution performance of suspended rGO/g-C3N4 photocatalysts

The combination of graphene and semiconductor photocatalysts such as graphitic carbon nitride (g-C3N4) has been widely demonstrated as an effective strategy to improve the H2-evolution performance of photocatalysts. However, owing to the hydrophobicity of graphene, the green synthesis of well-suspended graphene/g-C3N4 in the absence of surfactant or additives is still a challenge. In this study, the suspended reduced-graphene-oxide-modified g-C3N4 (rGO/g-C3N4) photocatalysts were fabricated through an in situ hydrothermal synthesis route, which includes a facile preparation of well-coupled GO/g-C3N4 precursor and its following in situ transformation to form the rGO/g-C3N4 by a hydrothermal reduction method. It was found that the obtained rGO/g-C3N4 photocatalysts showed a cotton-like structure and could be well suspended in water owing to the well coupling between rGO and g-C3N4 nanosheets, which is quite favorable for the photocatalytic reactions in an aqueous solution system. After loading Pt cocatalyst as the active site for H2 evolution reaction, the rGO/g-C3N4 composite photocatalysts exhibited an obviously improved performance (ca. 23.7%) by the addition of a small amount of rGO (0.08%), compared with the pure g-C3N4. The improved photocatalytic H2-evolution performance of rGO/g-C3N4 composite can be attributed the synergistic effect of rGO nanosheets and Pt nanoparticles, namely, rGO nanosheet acts as an electron-transfer mediator to rapidly capture the photogenerated electrons from the g-C3N4 and then transfer to the Pt cocatalyst, while the Pt nanoparticle functions as a reduction active site to promote the H2-evolution reaction effectively. Considering its green preparation and high photocatalytic performance, the present synthesis route of suspended rGO/g-C3N4 may provide new insights into design and fabrication for other composite materials with various potential applications.

BiVO4/g-C3N4 composite visible-light photocatalyst for effective elimination of aqueous organic pollutants

BiVO4/g-C3N4 composite photocatalysts were successfully synthesized by sonification and the chemical structures of BiVO4/g-C3N4 heterostructures are characterized systematically. The photocatalytic activity of BiVO4/g-C3N4 for rhodamine B (RhB) and p-nitrophenol (PNP) degradation is evaluated under visible light irradiation. It has been found that the novel BiVO4/g-C3N4 composites exhibit excellent catalytic activities towards RhB and PNP degradation, and these BiVO4/g-C3N4 composites are much more active compared with that of pure g-C3N4. Activity enhancement after BiVO4 introducing is mainly attributed to the better optical absorption ability over the well contacted structure in heterojunctions, good adsorption ability of organic contaminants and lower recombination rate of electron-hole pairs. In addition, in BiVO4/g-C3N4-based visible-light system OH radical, not active in pure g-C3N4 system, is also found to be active species for pollutants degradation, which may be another evidence for the enhanced photocatalytic activity by BiVO4 introduction. Furthermore, the most active 10wt.% BiVO4/g-C3N4 photocatalyst exhibits enough catalytic stability in recycle test, showing great potential as cost-effective heterogeneous visible-light photocatalyst for aqueous organic contaminants elimination in future applications.

Facile preparation of Z-scheme WO3/g-C3N4 composite photocatalyst with enhanced photocatalytic performance under visible light

Visible-light-driven WO3/g-C3N4 composites photocatalysts were synthesized via a facile one-step simultaneously heating procedure with urea as the main precursor. These prepared catalyst samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), transmission electron microscopy (TEM), N2 adsorption, ultraviolet-visible diffuse reflection spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the WO3/g-C3N4 composites was evaluated by the photo-degradation of Rhodamine B (RhB) under visible light irradiation. The results indicated that the composites with 25wt.% WO3 content exhibited highest photocatalytic activity compared to pure WO3, bare g-C3N4 and other WO3/g-C3N4 composites. The favorable photocatalytic activity of WO3/g-C3N4 composites was mainly attributed to the excellent surface properties, enhanced visible-light absorption and the desirable band positions. A possible Z-scheme photocatalytic mechanism was proposed based on structure and electrochemical characterizations results, which can well explain the enhanced migration rate of photogenerated electrons and holes in WO3/g-C3N4 heterojunctions.

In-situ synthesis of highly efficient visible light driven stannic oxide/graphitic carbon nitride heterostructured photocatalysts

Novel and efficient visible-light-driven stannic oxide/graphitic carbon nitride heterostructured photocatalysts are prepared via a simple in-situ solvothermal method. Characterization results demonstrate that there exist strong interactions between SnO2 nanoparticles and g-C3N4 matrix, which indicates the formation of SnO2/g-C3N4 heterojunction. The as-synthesized SnO2/g-C3N4 composite exhibits improved efficiency for photodegradation of rhodamine B in aqueous solutions, with an apparent rate constant 6.5 times higher than that of commercial TiO2 (Degussa P25). The enhanced photocatalytic activity is attributed to synergistic effect between SnO2 and g-C3N4, resulting in effective interfacial charge transfer and prolonged charge-hole separation time. Moreover, SnO2/g-C3N4 composite photocatalysts possess excellent durability and stability after 6 recycling runs, and a possible photocatalytic mechanism is also proposed. This research highlights the promising applications of two dimensional g-C3N4 based composite photocatalysts in the field of waste water disposal and environmental remediation.

W18O49 nanowires grown on g-C3N4 sheets with enhanced photocatalytic hydrogen evolution activity under visible light

A hybrid nanomaterial comprising of one-dimensional W18O49 nanowires grown on two-dimensional g-C3N4 sheets was prepared by a facile solvothermal process. Photocatalytic activity of these materials for H2 generation under visible light was evaluated. The optimum efficiency of W18O49/g-C3N4 composite photocatalyst at a mass content of 30% was up to 4.5 times as high as that of the pure g-C3N4. The significantly enhanced performance of W18O49/g-C3N4 composites was mainly attributed to the synergistic effect between the interface of W18O49 nanowires and g-C3N4 sheets, involving stronger light absorption in the visible range, faster transfer and more efficient separation of the photo-generated electron-hole pairs. In short, the W18O49/g-C3N4 hybrid nanomaterial was demonstrated to be an effective photocatalyst for H2 production.

Enhanced disinfection application of Ag-modified g-C3N4 composite under visible light

Ag/g-C3N4 composite photocatalyst, which was synthesized by thermal polymerization of melamine precursor combined with the photo-assisted reduction method, was applied as an efficient visible-light-driven photocatalyst for inactivating Escherichia coli (E. coli). The composite photocatalysts exhibited significantly enhanced photocatalytic disinfection efficiency than pure g-C3N4 powders. The mechanism of enhanced disinfection activity was systematically investigated by UV–visible diffuse reflectance spectra, photoluminescence spectra, and photo-electrochemical methods including photogenerated current densities, electrochemical impedance spectroscopy (EIS) spectra and Mott–Schottky plots. The enhanced photocatalytic bactericidal effect was attributed to the hybrid effect from Ag and g-C3N4, which resulted in enhanced adsorption of visible light, reduced recombination of free charges, rapid separation and transportation of photogenerated electrons–holes. The disinfection mechanism was studied by employing chemical scavengers and ESR technology, indicating the important role of h+ and e−. Considering the bulk availability and excellent disinfection activity of Ag/g-C3N4, it is a promising solar-driven photocatalyst for cleaning microbial contaminated water in practice.

The flux growth of single-crystalline CoTiO3 polyhedral particles and improved visible-light photocatalytic activity of heterostructured CoTiO3/g-C3N4 composites.

Highly crystalline and idiomorphic CoTiO3 single crystals with a well-defined polyhedral morphology were grown successfully for the first time by a facile flux method. Herein, the effects of the molten salt type and cobalt precursor on the phase composition, crystallization habit and morphology of the CoTiO3 products were also investigated. Importantly, using the flux-grown CoTiO3 crystal as the visible-light sensitizer due to its narrow band gap to couple with graphitic carbon nitride (g-C3N4) by a direct in situ thermal induced polycondensation route, novel CoTiO3/g-C3N4 composite photocatalysts were obtained. The as-synthesized samples were systematically characterized by XRD, EDS, SEM, TEM, SAED, HRTEM, FT-IR, XPS, DRS and PL techniques. The results revealed that CoTiO3 polyhedral crystals were closely combined with g-C3N4 nanosheets leading to the formation of a heterojunction structure at the interface between CoTiO3 and g-C3N4. Photocatalytic evaluation showed that the heterostructured CoTiO3/g-C3N4 composite exhibited much higher photocatalytic activity for the degradation of methyl orange under visible light irradiation than that of individual CoTiO3 and g-C3N4, which could be mainly ascribed to the synergistic effect between CoTiO3 and g-C3N4, including the enhanced visible-light harvesting ability and more efficient separation and longer lifetime of photogenerated charge carriers. Furthermore, the composite photocatalyst showed an excellent stability and reusability during four successive cycles. Finally, a possible mechanism responsible for the charge separation and improved photocatalytic activity was proposed.

Constructing a novel ternary Fe(III)/graphene/g-C3N4 composite photocatalyst with enhanced visible-light driven photocatalytic activity via interfacial charge transfer effect

Interfacial charge transfer effect (IFCT) was introduced into g-C3N4 by grafting Fe(III) species on its surface via a simple impregnation method. It has been shown that the obtained Fe(III)-grafted g-C3N4 photocatalyst exhibited enhanced visible-light absorption, reduced charge recombination and improved photocatalytic activity as compared with those of g-C3N4, due to the interfacial charge transfer between the Fe(III) species and g-C3N4. Furthermore, a novel ternary Fe(III)/graphene/g-C3N4 photocatalyst was successfully constructed by integrating graphene into the binary Fe(III)/g-C3N4 composite as the electron mediator. It has been found that the introduction of graphene made the Fe species show well distribution, smaller size and relatively high content in the ternary photocatalyst as compared with those in the binary one, revealing a synergistic effect between the Fe(III) species and graphene existed in the ternary photocatalyst. Consequently, the photocatalytic activity of the ternary Fe(III)/graphene/g-C3N4 photocatalyst was superior to that of the binary one, originating from its stronger visible-light absorption and more reduced charge combination. The ternary composite that consists of transition metal, graphene and g-C3N4 represents a new kind of high-efficiency visible-light-driven photocatalysts for water disinfection.

Disinfection capability of Ag/g-C3N4 composite photocatalysts under UV and visible light illumination

The biocidal capability of Ag/g-C3N4 composite photocatalysts against Escherichia coli was evaluated as a function of the Ag content of the material upon UV and visible light excitation. The Ag/g-C3N4 composite system shows significant biocidal activity, presenting a behavior with a strong dependence on the silver content as well as on the excitation wavelength. The physico-chemical characterization of the samples together with a Langmuir–Hinshelwood-type kinetic modelling of biocidal experiments and the (photoluminescence and electron paramagnetic resonance) analysis of charge handling properties of the solids were used to interpret the photocatalytic response of the composite materials. The overall analysis shows that the wavelength dependence observed for all Ag/g-C3N4 composite photocatalysts is strongly correlated with the semiconductor—metal heterojunction effect on charge separation, handling and recombination, indicating the key role of the cooperative action between the two components of the system. Such cooperative effect is studied along the sample series and discussed to be related to the efficient use of both hole and electron related species in the disinfection action.