Efficient Electron-hole Separation Research Articles

Photogenerated carriers transfer in Pd/TiO2-AgO heterojunction and its photocatalytic behaviors on oxidative dehydrogenation of ethane to ethylene

Photocatalytic oxidative dehydrogenation of ethane to ethylene with a high selectivity is an attractive reaction. In this study, different types of heterojunctions between Pd/TiO2 and a second metal oxide semiconductor were designed and synthesized to realize high activity conversion of C2H6 to C2H4. Pd/TiO2-AgO heterojunction was proved with best reaction performance. The addition of AgO facilitated the activation of reactant molecules. It enhanced directional transfer of electron-hole pairs and separation efficiency of photogenerated carriers. Pd/TiO2-5 % AgO heterojunction was proved with the best separation ability of photogenerated carriers and the largest number of surface hydroxyl groups. Detailed charge transfer path and reaction mechanism were proposed and discussed.

Facile preparation of ZIF-67 on TiO2 and enhancement photocathodic protection for 316L stainless steel

Photocathodic protection (PCP) anticorrosion using sunlight is a green and sustainable technology. However, the ease of carriers compounding and the low light utilization are still the main restraints to its development. To develop an effective photoanode, a metal-organic framework (MOF, i.e., ZIF-67) material is electrodeposited and grown in-situ on TiO2 nanorods. The morphological structure, light absorption properties, photoelectrochemical properties and cathodic protection principle of ZIF-67/TiO2 photoanode are analysed by SEM, PL, I-V and EIS. The material characterization and light absorption characteristics show that the photoanode has good light absorption performance and higher electron hole separation efficiency. Photoelectrochemical test shows that ZIF-67/TiO2 photoanode has excellent photocathodic protection for 316L stainless steel (316L SS). ZTRs-60 has the optimal protection effect. Under simulated sunlight, the OCP of 316L SS coupled ZTRs-60 is -0.41 V vs. Ag/AgCl, and the current density of the I-t curve can reach 20 μA/cm2. EIS and Tafel tests show that the photogenerated electrons transfer to the stainless steel surface, which promotes the cathode polarization process and alleviates the metal corrosion.

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

Research progress on ZnO/MoS2/rGO ternary photocatalysts

Energy shortages and environmental pollution have become one of the important global issues, and semiconductor photocatalytic technology is considered one of the most effective means to solve these problems. As a new and efficient green material, ZnO has attracted wide attention. ZnO is widely used in the field of photocatalysis due to its non-toxicity, low cost, environmental friendliness, adjustable band gap, high electron density, and chemical stability. However, the recombination of photogenerated charge carriers in ZnO hinders its practical application and lowers the utilization efficiency of visible light. On the other hand, molybdenum disulfide/reduced graphene oxide (MoS2/rGO), as a binary non-precious metal co-catalyst, has a larger specific surface area, suitable band gap width, and visible light response capability compared to a single-phase graphene co-catalyst. Therefore, introducing the MoS2/rGO co-catalyst into the ZnO system can provide more active sites, reduce the probability of photogenerated charge carrier recombination, and improve the utilization efficiency of visible light. In this review, we summarize the hydrothermal synthesis methods for preparing this highly demanded nanocomposite material, including one-step and stepwise methods. Subsequently, we elaborate on the mechanism of enhancing light absorption and achieving efficient electron-hole separation behavior in the ternary system heterojunction structure during the photocatalytic process. Due to its significant advantages, this ternary system heterojunction structure has been widely applied in the field of photocatalysis, including applications such as pollutant degradation, sterilization, and water splitting.

Acid modification on ZnIn2S4 with sulfur vacancy for highly efficient photocatalytic reduction of Cr(VI)

Anion vacancies caused by acid treatment over photocatalysts have significant influences on photocatalytic processes. In this study, the ZnIn2S4 (denoted as ZIS) nanoflower samples were synthesized using a one-step hydrothermal process and then impregnated with different amounts of nitric acid solutions. The gathered samples were characterized using XRD, SEM, XPS, BET, and EPR, and their photocatalytic reduction activity of Cr(VI) was also studied. Owing to defect structures, the removal of Cr(VI) of sulfur-rich vacancies ZIS-NA-3 reached nearly 100% within 90 min under simulated solar light, which was about 3 times greater than that of the original ZIS. In summary, this study confirmed that nitric acid treatment could form a defect state on the surface of catalysts, enhancing the light absorption range and improving the electron-hole pair separation efficiency. Furthermore, the stability and recycling of the ZIS-NA-3 catalysts were evaluated. This work offered a simple surface modification technique for constructing high-activity photocatalysts so as to achieve the purpose of removal from polluted wastewater containing Cr(VI).

A covalent organic framework integrating photocatalytic center and electron reservoir for photocatalytic CO2 reduction to HCOOH

Direct and efficient photocatalytic conversion of CO2 into fuels and high value-added chemicals under sunlight is of great significance in alleviating the energy crisis and environmental issues. Covalent organic frameworks (COFs) have attracted much attention in the photocatalytic field as materials that can be pre-designed on demand. Taking advantage of the pre-designable properties of COFs materials, the integration of organic building blocks with photocatalytic activity and photoelectron-resident properties into frameworks can improve the electron-hole separation efficiency and photocatalytic performance. Here, we report a newly designed COF (COF-TVBT-N) with triazine and alkenyl groups that can be used as a photocatalyst to accomplish the photoreduction of CO2 to HCOOH under simulated sunlight without the assistance of metal sites and photosensitizers. Furthermore, we unambiguously reveal that the photocatalytic active center in COF-TVBT-N is TVBT through the combination of experiments and theoretical calculations. DFT calculations suggest that the adsorption of H near the active center is beneficial for the adsorption and photoreduction of CO2 in this photocatalytic system. The photoexcitation process and photocatalytic CO2 reduction mechanism of COF-TVBT-N are also reasonably deduced based on DFT calculations. This work provides ideas for the design of COFs as photocatalysts for CO2 reduction and gives insights into the mechanism of CO2 conversion to HCOOH.

Narrow Bandgap Schottky Heterojunction Sonosensitizer with High Electron-Hole Separation Boosted Sonodynamic Therapy in Bladder Cancer.

Sonodynamic therapy (SDT) is applied to bladder cancer (BC) given its advantages of high depth of tissue penetration and nontoxicity due to the unique anatomical location of the bladder near the abdominal surface. However, low electron-hole separation efficiency and wide bandgap of sonosensitizers limit the effectiveness of SDT. This study aims to develop a TiO2-Ru-PEG Schottky heterojunction sonosensitizer with high electron-hole separation and narrow bandgap for SDT in BC. Density functional theory (DFT) calculations and experiments collectively demonstrate that the bandgap of TiO2-Ru-PEG is reduced due to the Schottky heterojunction with the characteristic of crystalline-amorphous interface formed by the deposition of ruthenium (Ru) within the shell layer of TiO2. Thanks to the enhancement of oxygen adsorption and the efficient separation of electron-hole pairs, TiO2-Ru-PEG promotes the generation of reactive oxygen species (ROS) under ultrasound (US) irradiation, resulting in cell cycle arrest and apoptosis of bladder tumor cells. The in vivo results prove that TiO2-Ru-PEG boosted the subcutaneous and orthotopic bladder tumor models while exhibiting good safety. This study adopts the ruthenium complex for optimizing sonosensitizers, contributing to the progress of SDT improvement strategies and presenting a paradigm for BC therapy.

Peroxymonosulfate enhanced photocatalytic degradation of organic dye by metal-free TpTt-COF under visible light irradiation

Recently, the activation of persulfate (PDS) by non-metallic photocatalysts under visible light has attracted significant interest in applications in environmental remediation. This study presents a pioneering investigation into the combined application of the TpTt-COF and PMS for visible light degradation of organic dyes. Synthesized orange TpTt-COF monomers exhibit exceptional crystallinity, a 2D structure, and notable stability in harsh conditions. The broad visible light absorption around a wavelength of 708 nm. The TpTt-COF emerges as a promising candidate for photocatalytic dye degradation. The study addresses high charge recombination in the TpTt-COF, highlighting the crucial role of its electron donor and acceptor for the PMS activation. Comparative analyses against traditional photocatalytic materials, such as the metal-free carbon-based material g-C3N4 and transition metal-containing TiO2, demonstrate TpTt-COF's superior performance, generating diverse free radicals. In simulated experiments, the TpTt-COF's degradation rate surpasses PMS-combined g-C3N4 by 13.9 times. and 1.6 times higher than the TpTt-COF alone. Remarkably, the TpTt-COF maintains high activity under harsh environments. Investigations into the degradation mechanism and the TpTt-COF's reusability reveal its efficiency and stability. Under visible light, TpTt-COF facilitates efficient electron–hole separation. Combining the TpTt-COF with PMS produces various radicals, ensuring effective separation and a synergistic effect. Radical quenching experiments confirm the pivotal role of O2-· radicals, while ·OH and SO4-· radicals intensify the degradation. After five cycles, TpTt-COF maintains an impressive 83.2% degradation efficiency. This study introduces an efficient photocatalytic system mediated by PMS and valuable insights into governing mechanisms for organic pollutant degradation in water environments.

2D Copper–Porphyrin Metal–Organic Framework Nanosheet‐Photosensitized TiO2 for Efficiently Broadband Light‐Driven Conversion of CO2 to CH4

The effective utilization of light is crucial in the use of the solar energy for CO2 conversion into valuable fuels and chemicals, in which improving the photocatalytic materials’ capacity to absorb light is a key. Herein, a 2D copper–porphyrin metal−organic framework (MOF)‐photosensitized titania, TiO2/Zn–CuTCPP, is reported, which can absorb wide range of light and photoreduce CO2 with high efficiency under full spectrum irradiation. Fluorescence spectral analysis elucidates the relationship between the photocatalytic activity and the electron–hole separation efficiency. In addition, mechanistic information obtained from electron paramagnetic resonance and in situ infrared analyses demonstrates that the presence of Cu–N4 site in the MOF structure is conducive to the generation of hydrogen free radicals (•H), which plays a key role in the formation of intermediates, thus facilitating the hydrogenation in the reaction process. Consequently, TiO2/Zn–CuTCPP significantly enhances the photocatalytic conversion of CO2 into CH4 with a yield 14 times higher than that of P25.

Layered double hydroxides derived prussian blue analogue nanocage confining NiCoP nanoparticles as efficient bifunctional electrocatalyst

Designing novel electrocatalysts with excellent catalytic activity for efficient water splitting is necessary to achieve the large-scale H2/O2 production from renewable resources. In this study, a facile hydrothermal method followed by low-temperature phosphorylation treatment was employed to fabricate a nanocage of prussian blue analogue encapsulating NiCoP nanoparticles (NiCoP@PBA), which was derived from the layered double hydroxide precursor. As a bifunctional non-precious metal electrocatalyst, NiCoP@PBA demonstrates superior performance in KOH electrolyte water splitting, with overpotentials of 59 mV for electrocatalytic hydrogen evolution reaction (HER) and 263 mV for oxygen evolution reaction (OER) at 10 mA cm−2. The catalyst also exhibits low Tafel slopes of 54 mV dec−1 for HER and 120 mV dec−1 for OER, reflecting efficient charge transfer kinetics. DFT simulations show that the Co–N moieties at the heterogeneous interface of NiCoP@PBA can optimize the surface electron distribution and energy states, thus facilitating efficient electron-hole pair separation, significantly enhancing catalytic activity for both HER and OER process, and significantly extending the electrocatalyst's service life. Our approach can be extended to more non-precious metal electrocatalysts, which is significant for the design of efficient bifunctional water splitting electrocatalysts.

BiOCl/BiOBr composites for efficient photocatalytic carbon dioxide reduction

BiOBr (BOB) photocatalysts have low photocatalytic CO2 reduction performance due to their low electron-hole pair separation efficiency. To improve this problem, BiOCl (BOCl) is used as a co-catalyst. BOCl is loaded into BOB to form BiOCl/BiOBr (BOCl/BOB) type Ⅰ heterojunction, which enhances the photocatalytic CO2 reduction performance of BOB by promoting the separation of photogenerated electrons and holes. The results of TPR and PL experiments show that the 20% BOCl/BOB composites have the highest photogenerated carrier separation rate, and the results of CO2 reduction experiments show that 20% BOCl/BOB composites have the best photocatalytic CO2 reduction performance of 7.353 μmolg−1h−1, which is 3.22 and 1.99 times higher than pure BOB and BOCl, respectively. This work provides an effective reference for the development of modified photocatalysts.

NH2-UiO-66 modification BiOBr enhancement photoreduction CO2 to CO

As a typical semiconductor catalyst, BiOBr has an advisable bandgap, superior light absorption properties, and a unique laminated structure. However, the slow electron-hole separation rate results in poor CO2 reduction performance. To enhance the photocatalytic efficiency of BiOBr, this study constructs BiOBr heterojunctions with Lewis basic groups by loading NH2-UiO-66 on BiOBr. The BiOBr/NH2-UiO-66 heterojunction have been built and possess stronger light response, larger specific surface area and electron-hole separation efficiency compared to pure BiOBr and NH2-UiO-66. The optimal BiOBr/NH2-UiO-66 displays that the CO yield is 9.19 μmol g-1h−1, which is 4 times higher than pure BiOBr.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3.

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Dynamic Ag-mediated electron transfer confined ZnO nanorods for boosted photocatalytic bacterial disinfection

Infectious diseases, particularly bacterial infections, pose a global crisis with significant impacts on public health and economic stability due to the emergence of multi-drug resistance and limitations in existing therapeutic options. The present study focused on the development of photocatalytic disinfectant and silver-decorated hexagonal zinc oxide nanorods (Ag/ZnO NRs) were fabricated through an ultrasonic-assisted solvothermal method, and investigated for the photocatalytic inactivation on E. coli. The morphological, structural, and optical characteristics of the fabricated Ag/ZnO NRs were systematically studied through various analytical techniques. Here, 3%Ag/ZnO NRs showed 96.9% inactivation of E. coli within 120 min of visible light irradiation. The excellent inactivation efficiency of the photocatalyst could be attributed to the higher charge carrier mobility, efficient electron-hole pair separation, and highvisible light harvesting ability. The Schottky heterojunction was proposed as a possible mechanism for the photoinactivation of E. coli. Further, the impacts of different dosages of nanocomposites (NCs) and varying pH on bacterial inactivation were studied under visible light exposure. The reusability and stability of the NCs were investigatedfor 6 consecutive cycles of photoinactivation and it showed excellent efficiency (91.16%) of the photocatalyst for prolonged usage. The real-time application was assessed using reclaimed wastewaterand the influence on the organic matter was determined using COD analysis. The proposed study offers a significant point reference for the practical application of photocatalysis forthe inactivation of antibiotic-resistant microbes present in water bodies and environmental wastewater.

A signal amplification strategy based on hexametaphosphate-stabilized BiVO4@CdS heterojunction with Mg2+-modulated surface charge for CEA detection

An ultrasensitive sensor with excellent photoelectrochemical (PEC) properties was developed based on the combination of electrostatic interactions between the hexametaphosphate (HMP)-coated BiVO4@CdS novel photoelectric material and the electron donor. Compared with the conventional BiVO4@CdS photoactive material, the HMP-modified BiVO4@CdS not only increases the stability, but also utilizes the electrostatic interactions between the negative charge carried by the phosphate group and the electron donor, which results to a significant increase in the photoelectric conversion ability after Mg2+ incubation. Specifically, carcinoembryonic antigen (CEA)-targeted immunorecognition was combined with MgCO3 antibody labelling inspired by the ability of HMP to complex with Mg2+. The released Mg2+ from the MgCO3 tag could neutralize the negative charge on the surface of BiVO4@CdS-HMP, and the electrostatic repulsion with the electron donor was suppressed, accelerating the electron transfer, and thus improving the electron-hole separation efficiency. A sensitive detection capability was demonstrated with CEA as the model target. Featuring a wide linear detection range with a detection limit as low as 60 fg/mL, this work provides a fresh perspective on the development of high-performance PEC biosensors.

Modulating interface internal electric field for efficient charge separation in Co3O4/M-TiO2 p-n junction

The practical application of photocatalysis in water purification is restricted by the high electron-hole recombination efficiency. Herein, a Co3O4/M-TiO2 p-n composite catalyst with internal electric field (IEF) modulation was constructed. Because of the large number of oxygen vacancies (OVs) within Co3O4/M-TiO2, which could redistribute extra electrons to adjacent Co sites through the strong electron absorption effect of Co. Consequently, the charge distribution at the interface of Co3O4/M-TiO2 have been changed, forming positive and negative charge regions on M-TiO2 and Co3O4, respectively. Compared with Co3O4/P25, the amount of OVs in Co3O4/M-TiO2 is significantly increased, making the charge distribution at the interface more uneven and resulting in a significantly increased IEF intensity of Co3O4/M-TiO2 by 1.9 times. A series of photoelectric chemical experiments showed that driven by powerful IEF, the photogenerated electron-hole separation efficiency of Co3O4/M-TiO2 is significantly improved. In the photocatalysis-peroxymonosulfate (PMS) oxidation coupling system, Co3O4/M-TiO2 achieved high efficiency degradation of tetracycline hydrochloride (93.6 %) within 30 min, and a synergistic degradation mechanism of photocatalysis and PMS oxidation was proposed. This study provides a novel perspective on the construction of heterojunctions possessing strong internal electric fields.

Ulva lactuca L. extract bio-templated fabrication of CuO/ZnFe2O4 nanocomposites for photodegradation organic dye pollutants and in vitro biological activities

In this present work, a novel CuO/ZnFe2O4 nanocomposites has been fabricated via hydrothermal-assisted synthesis using Ulva lactuca L. extract as both a reducing and capping agent A comprehensive investigation such as structural, morphological, optical, and electronic properties of the CuO/ZnFe2O4 NCs were investigated in details. The photocatalytic efficacy of the prepared CuO/ZnFe2O4 NCs was assessed for Congo red (CR) dye degradation and the experimental results demonstrate the CuO/ZnFe2O4 NCs exhibits superior photocatalytic activity (91.13% k=0.03289 min−1) compared to pure CuO and ZnFe2O4 catalysts under 120 min of visible light irradiation. Additionally, the CuO/ZnFe2O4 NCs exhibited excellent long-term recycling stability over four consecutive cycles. This enhanced photocatalytic performance of CuO/ZnFe2O4 NCs was attributed to the synergism between CuO and ZnFe2O4, which facilitate the exceptional properties such as large specific area, a wide visible-light absorption range, and efficient electron-hole separation. Furthermore, the prepared CuO/ZnFe2O4 NCs were evaluated for their in vitro antibacterial and anticancer properties. The results of the disc diffusion assay with CuO/ZnFe2O4 NCs as an antibacterial agent demonstrated a highest zone of inhibition of 18.23 ± 0.30 mm for Bacillus subtilis and 19.83 ± 0.76 mm Escherichia coli. Moreover, in vitro cytotoxicity assessments using the MTT assay indicated a 64.94% cytotoxic activity against HT-29 colon cancer cells. The multifunctional advantages of Ulva lactuca L. extract-mediated green CuO/ZnFe2O4 NCs hold significant promise for environmental remediation and in vitro-based therapeutic applications.

Large‐Scale Solution‐Processed Ultrathin 2D Tri‐layer Heterostructures for Photodetector Applications

AbstractHeterojunction‐based photodetectors of 2D TMDs provide the solution‐processability and scalability to fabricate devices. In this study, we have produced photodetectors using a solution‐processable approach, focusing on the heterojunction of 2D transition metal dichalcogenides (TMDs). The photodetection properties of the fabricated devices have been thoroughly examined at two different wavelengths 660 nm and 785 nm. This hybrid 2D tri‐layer heterojunction strategy, employing a MoS2/MoSe2 heterojunction as the photosensitizer and a TiS2 layer as the conducting pathway, is fabricated to understand high‐performance photodetectors. A simple and low‐cost solution process was used to fabricate all the active layers of the photodetector. 2D TMDs were synthesized by liquid phase exfoliation which exhibits absorption in both visible as well as NIR spectral regions. The as‐fabricated photodetector shows a response time of 220 msec and responsivity of ~28 mA W−1 in the visible region and ~44 mA W−1 in the near IR region. This improved response of the as‐fabricated photodetector of tri‐layer heterojunction results from the effective decrease in recombination rate and efficient electron–hole separation.

Crystal surfaces cooperate with F ion migration to improve the photocatalytic performance of Z-type Ag-Ag2S/F-TiO2 composites

The TiO2 has the problems of low utilization of visible light and high photogenerated carrier recombination rate. The photocatalytic activity of TiO2 can be significantly improved by introducing F ion and narrow band gap material Ag2S. When F ions are present on the {001} surface of TiO2, surface F ions drive positively charged holes across the {001} surface, creating a synergistic effect that promotes the separation of electron-hole pairs. During the sample composite process, a certain amount of Ag will be precipitated to form an all-solid Z-type heterojunction structure of Ag2S, Ag and F-TiO2, which can improve the electron-hole separation efficiency. The results of XPS characterization confirmed the migration of F ion and the precipitation of Ag. The Ag2S/F-TiO2 composite sample was referred to as AT for short, and the corresponding ratio was 1:10,1:20,1:30,1:40, the optimal sample AT 1:20 degraded 95.6% tetracycline hydrochloride within 2 hours. This work simultaneously realizes TiO2 self-modification (synergistic effect of F ion migration and TiO2{001} crystal surface) and composite modification (formation of all-solid Z-type heterojunction), a new idea of studying TiO2 self-modified cooperative heterostructures is proposed, and the good application potential of AT nanocomposites in photocatalytic water treatment technology is demonstrated.

One-Step Synthesis of Alkali Metal-Hydroxyl Double Modified Graphite Phase Carbon Nitride and Photocatalytic Degradation of Phenolic Compounds

In this work, potassium ion-hydroxyl double modified graphite phase carbon nitride (KCN–OH) was synthesized in one step by alkali hydrothermal (AH) method. The as-prepared catalysts were characterized by XRD, FT-IR, UV–Vis, N2 adsorption, SEM, XPS, PL, ESR, TPD and EIS. The introduction of potassium ion causes the reduced crystal size, increased specific surface area and promoted electron–hole separation efficiency of as-prepared catalyst. The hydroxyl group not only further improves the electron–hole separation efficiency but, as the electron donor group, can also make stronger interaction between catalyst and acidic phenolic compounds. The photocatalytic degradation of phenol was investigated under visible light. The results show that the phenol degradation rate constant of KCN–OH is 0.22 h[Formula: see text] under visible light, which is over 3.7 and 2.0 times higher than that of neat g-C3N4 and single hydroxyl-modified g-C3N4. KCN–OH also displays outstanding catalytic and structural stability. The possible reaction mechanism is discussed in this paper.