Highest Hydrogen Production Rate Research Articles

High-loaded sub-6 nm Cu catalyst with superior hydrothermal-stability and efficiency for aqueous phase reforming of methanol to hydrogen

Developing an efficient, hydrothermally stable and non-noble metal catalyst is a key for application of aqueous-phase reforming of methanol (APRM) to produce hydrogen in situ. Herein, a Cu@NC catalyst with high metal loading (44.9 wt %) and sub-6 nm Cu nanoparticle size was synthesized by pyrolyzing Cu-chitosan chelates. The coordination between metal ions (Cu2+) and amine functional groups in chitosan enabled high metallic dispersion in Cu-chitosan chelates. After pyrolysis, the Cu nanoparticles were embedded in N-doped carbon (NC) matrix. This confinement effect ensured remarkable hydrothermal stability for the Cu@NC catalyst. As a result, a high hydrogen production rate of 34.0 μmol·gcat−1·s−1 was obtained over Cu@NC-200 catalyst, about 12.6 times higher than that of a traditionally impregnated Cu/C catalyst. Notably, no deactivation and aggregation of Cu nanoparticle were observed after 200 h’ running in APRM, indicating excellent hydrothermal stability of the Cu@NC catalyst. Thus, this work developed a simple strategy to prepare an efficient and robust catalyst that could work well under hash hydrothermal conditions for application of APRM on the compact mobile devices.

Highly Active Palladium-Decorated Reduced Graphene Oxides for Heterogeneous Catalysis and Electrocatalysis: Hydrogen Production from Formaldehyde and Electrochemical Formaldehyde Detection.

The exploitation of highly efficient and stable hydrogen generation from chemical storage of formaldehyde (FA) is of great significance to the sustainable development of the future. Moreover, developing an accurate, rapid, reliable, and cost-effective catalyst for electrochemical detection of FA in solution is appealing. Herein, we report rational construction of Pd nanoparticles decorated reduced graphene oxides (Pd/rGO) nanohybrids not only as robust catalysts to produce hydrogen from alkaline FA solution and but also electrocatalysts for electrochemical detection of FA. By optimizing the reaction parameters including FA concentration, NaOH concentration and reaction temperature, Pd/rGO with Pd loading of 0.5 wt% could exhibit a high hydrogen production rate of 272 mL g−1min−1 at room temperature of 25 °C, which is 3.2 times that of conventional Pd NPs. In addition, as-prepared Pd/rGO nanohybrids modified glassy carbon (GC) electrodes are used as FA-detected electrochemical sensors. A sensitive oxidation peak with a current density of 8.38 mA/cm2 was observed at 0.12 V (vs. Ag/AgCl) in 0.5 M NaOH containing 10 mM FA over Pd/rGO catalysts with Pd loading of 0.5 wt%. The results showed the prepared Pd/rGO nanocatalyst not only exhibited efficient and stable hydrogen production from alkaline FA solution but also had good electrocatalytic properties with respect to formaldehyde electrooxidation as a result of the synergistic effect of Pd NPs and rGO nanosheets.

Dark-fermentative hydrogen production from synthetic lignocellulose hydrolysate by a mixed bacterial culture: The relationship between hydraulic retention time and pH conditions

This study assessed the effect of hydraulic retention time (HRT) ranging from 24 to 3 h on continuous dark-fermentative H2 production in four bioreactors operated at pH 5.0, 5.5, 6.0 and 6.5. A mixture of cellobiose, xylose and arabinose was used as the substrate. The highest hydrogen production rate between HRTs of 24 and 12 h was observed at pH 6.5, while at HRT below 12 h at pH 6.0. At a HRT of 3 h it reached 11.4 L H2/L-d. Thus, the optimum pH for H2 production depends on the HRT. The highest sugar utilization was obtained at pH 6.0 and 6.5 and decreased in the following order: cellobiose > xylose > arabinose. The pH conditions, in contrast to HRT, were found to have a significant influence on the bacterial composition. Low diversity in bacterial culture dominated by the Clostridium genus allows for stable and high H2 production performance.

Principal component analysis and response surface methodology: optimization for H2 evolution from water catalyzed adopting V–Bi under visible light

Energy generation by photocatalytic water splitting with semiconductors under visible light is an effective method for generating pollution-free energy. In this work, a highly efficient vanadium pentoxide (V2O5)-based composite photocatalyst was prepared by hydrothermal calcination. The preparation conditions were optimized using single factor experiments, factor analysis (FA), principal component analysis (PCA), and response surface method (Design Expert). The results showed that the optimal preparation conditions were 6% Bi2S3 loading, 10 h hydrothermal time, 175.0°C hydrothermal temperature, 4.0 h calcination time, and a calcination temperature of 400.0°C. The results of FA and PCA analysis showed that the hydrothermal temperature, calcination time, and calcination temperature were the three main influencing factors. According to the optimization analysis using the response surface method, the highest hydrogen production rate (590.151 μmol/(g۰h)) was obtained at a hydrothermal temperature of 168.74°C, a calcination time of 3.97 h, and a calcination temperature of 390.15°C. The quantum yield of the catalyst was 27.71%.

Synergetic photocatalytic and thermocatalytic aqueous phase reforming of methanol for hydrogen production based on noble metal/photosensitive supports catalysts

To overcome high Gibbs free energy and low reaction rate of thermal catalytic and photocatalytic hydrogen production from methanol-H2O mixture, photo-thermal synergistic catalysis (PC-TC) reforming has proved to be an effective strategy owing to the photo-assited thermal synergistic effect to accelerate the step controlling kinetic behavior. In order to efficiently produce H2, proper photosensitive catalysts which absorb light energy and also show efficient thermal catalytic (TC) performance need to be developed. To study the designing principle for catalysts, herein we incorporate Pt/Pd and three different supports which show similar band gaps (ZnO, CeO2, and P25) through the in-situ photo-deposition, which act as catalysts for PC-TC methanol aqueous reforming. The resultant 0.1%Pt/P25 catalyst exhibits H2 evolution activity ∼3.1 times than that of the TC condition and ∼5.5 times than that of the photocatalytic reforming (PC) condition in the proposed PC-TC process; meanwhile 0.1%Pt/ZnO and 01%Pt/CeO2 under PC-TC condition show ∼1.3 times and ∼2.0 times than that of the catalytic performance under TC condition. The physical characterizations prove that the metal-support interaction and the supports may be key factors for the catalytic performance. The active intermediate trapping experiments demonstrate possible intermediates in the PC-TC process and established reaction mechanisms to explain the synergetic effect for improved efficiency of hydrogen production. These findings may open up a new avenue of designing catalysts based on semiconductors for the PC-TC reforming of methanol-water to produce hydrogen in a high-efficiency and low-cost way, serving the needs of the future hydrogen economy.

Identifying the realistic catalyst for aqueous phase reforming of methanol over Pt supported by lanthanum nickel perovskite catalyst

In-situ supply of H2 by aqueous phase reforming (APR) of methanol is promising but still challenging due to the unsatisfied activity and stability of catalyst. Herein, we prepared lanthanum nickel perovskite supporting Pt catalysts and evaluated their performance in methanol APR. A transformation from lanthanum nickel perovskite into LaCO3OH happened after APR. The characterizations results reveal that these two perovskite catalysts transformed into LaCO3OH supporting Pt and NiOx structure. We further prepared Pt-NiOx/LaCO3OH catalyst to verify it. Combining with temperature programmed surface reaction, a possible mechanism is proposed. The transformed catalyst possessed more metallic Pt sites and more abundant active OH groups, which are beneficial for methanol decomposition and CO shift, respectively. In addition, although the structure transformation happened for perovskite supporting Pt catalyst, it presented extremely excellent stability with only 7% loss of its highest rate of hydrogen production after 315 h on stream.

Single-atom Ir and Ru anchored on graphitic carbon nitride for efficient and stable electrocatalytic/photocatalytic hydrogen evolution

Renewable energy-powered water electrolysis and photocatalytic water splitting are two promising approaches to green hydrogen production. Electrocatalysts and photocatalysts are essential components determining the performance of water electrolyzers and photocatalytic reactors, respectively. Currently, there is a pressing need to develop efficient and stable electrocatalysts and photocatalysts for large-scale deployment of these devices to reach carbon neutrality. Herein, we report the synthesis of single-atom Ir and Ru anchored on mesoporous graphitic carbon nitride (Ir-g-CN and Ru-g-CN), which can be used as electrocatalysts and photocatalysts for the hydrogen evolution reaction (HER). Remarkably, Ru-g-CN shows a high turnover frequency (TOF) of 12.9 and 5.1 s−1 at an overpotential (η) of 100 mV in 0.5 M H2SO4 and 1.0 M KOH, respectively, outperforming Ir-g-CN, commercial Pt/C benchmark and many other advanced HER catalysts reported recently. Moreover, Ru-g-CN can deliver an exceptionally high mass activity of 24.55 and 8.78 A mg−1 at η = 100 mV in acidic and alkaline solutions, meanwhile exhibiting a high apparent current density, which is favorable for practical applications. Additionally, both Ru-g-CN and Ir-g-CN show outstanding catalytic stability, continuously catalyzing the HER in acidic and alkaline conditions for 120 h with minimal degradation. Besides, when used for photocatalytic water splitting, Ru-g-CN can achieve a high hydrogen production rate of 489.7 mmol H2 gRu−1 h−1, and shows good photocatalytic stability. Our density functional theory (DFT) calculations demonstrate that loading Ir and Ru single-atoms on g-CN alters the electronic structure, resulting in a reduced bandgap and improved electrical conductivity, facilitating electron transfer during the catalysis. Moreover, the Gibbs free energy of hydrogen adsorption on Ru-g-CN and Ir-g-CN is also substantially lowered, enhancing HER performance.

Extracting high-purity hydrogen via sodium looping-based formic acid dehydrogenation

Formic acid (FA) has been considered as a prospective hydrogen carrier for its potentials to realize hydrogen storage, transportation, and in-situ supply under mild conditions. However, the application of FA dehydrogenation is limited by its unsatisfactory hydrogen concentration and carbon monoxide selectivity. Herein, a sodium looping-based (Na 2 CO 3 ↔NaHCO 3 ) formic acid dehydrogenation (SLFAD) system is proposed for high-purity hydrogen production with ultra-low CO generation via the Na 2 CO 3 ↔NaHCO 3 looping. The SLFAD system consists of three parts, which are FA dehydrogenation reactor (FADR), sorption-enhanced carbon oxide removal reactor (CORR), and sodium-based sorbent regeneration reactor (SSRR). Experimental results proved that no sodium formate and sodium oxalate was formed under NaHCO 3 reduction by H 2 . A comprehensive assessment of the system was carried out to preliminary verify the feasibility and optimize the operation parameters of the SLFAD system. Results indicated that a maximum hydrogen concentration of 97.905 vol%, a minimum CO concentration of 11.97 ppm, and a high hydrogen production rate of 0.99989 kmol H 2 h −1 can be obtained under the conditions of atmospheric pressure, FADR temperature at 80 °C, H 2 O/HCOOH = 1.2, CORR temperature at 80 °C, and Na 2 CO 3 /HCOOH = 1.0. • A sodium looping based formic acid dehydrogenation (SLFAD) concept was proposed. • A high hydrogen concentration of 97.90 vol% can be obtained at low temperatures. • Carbon monoxide concentration can be restricted to be 11.97 ppm via SLFAD process. • Sodium-based absorbent can be regenerated with the achievement of CO 2 capture.

A strategy of mid-temperature natural gas based chemical looping reforming for hydrogen production

Steam methane reforming (SMR) needs the reaction heat at a temperature above 800 °C provided by the combustion of natural gas and suffers from adverse environmental impact and the hydrogen separated from other chemicals needs extra energy penalty. In order to avoid the expensive cost and high power consumption caused by capturing CO 2 after combustion in SMR, natural gas Chemical Looping Reforming (CLR) is proposed, where the chemical looping combustion of metal oxides replaced the direct combustion of NG to convert natural gas to hydrogen and carbon dioxide. Although CO 2 can be separated with less energy penalty when combustion, CLR still require higher temperature heat for the hydrogen production and cause the poor sintering of oxygen carriers (OC). Here, we report a high-rate hydrogen production and low-energy penalty of strategy by natural gas chemical-looping process with both metallic oxide reduction and metal oxidation coupled with steam. Fe 3 O 4 is employed as an oxygen carrier. Different from the common chemical looping reforming, the double side reactions of both the reduction and oxidization enable to provide the hydrogen in the range of 500–600 °C under the atmospheric pressure. Furthermore, the CO 2 is absorbed and captured with reduction reaction simultaneously. Through the thermodynamic analysis and irreversibility analysis of hydrogen production by natural gas via chemical looping reforming at atmospheric pressure, we provide a possibility of hydrogen production from methane at moderate temperature. The reported results in this paper should be viewed as optimistic due to several idealized assumptions: Considering that the chemical looping reaction is carried out at the equilibrium temperature of 500 °C, and complete CO 2 capture can be achieved. It is assumed that the unreacted methane and hydrogen are completely separated by physical adsorption. This paper may have the potential of saving the natural gas consumption required to produce 1 m 3 H 2 and reducing the cost of hydrogen production. • A mid-temperature chemical looping reforming hydrogen production method via natural gas was proposed. • We provide a possibility of methane hydrogen production from more than 800 °C to about 500 °C under atmospheric pressure. • This paper may have the potential of saving the natural gas consumption and reducing the cost of hydrogen production. • It would be combined with medium-temperature industrial waste heat or parabolic trough concentrating solar energy.

MoS2 and Fe2O3 co-modify g-C3N4 to improve the performance of photocatalytic hydrogen production

Photocatalytic hydrogen production as a technology to solve energy and environmental problems exhibits great prospect and the exploration of new photocatalytic materials is crucial. In this research, the ternary composite catalyst of MoS2/Fe2O3/g-C3N4 was successfully prepared by a hydrothermal method, and then a series of characterizations were conducted. The characterization results demonstrated that the composite catalyst had better photocatalytic performance and experiment results had confirmed that the MoS2/Fe2O3/g-C3N4 composite catalyst had a higher hydrogen production rate than the single-component catalyst g-C3N4, which was 7.82 mmol g−1 h−1, about 5 times higher than the catalyst g-C3N4 (1.56 mmol g−1 h−1). The improvement of its photocatalytic activity can be mainly attributed to its enhanced absorption of visible light and the increase of the specific surface area, which provided more reactive sites for the composite catalyst. The successful preparation of composite catalyst provided more channels for carrier migration and reduced the recombination of photogenerated electrons and holes. Meanwhile, the composite catalyst also showed higher stability and repeatability.

A Novel Chemical-Electrochemical Hydrogen Production from Coal Slurry by a Two-Step Process: Oxidation of Coal by Ferric Ions and Electroreduction of Hydrogen Ions.

Hydrogen production from the electrolysis of coal slurry is a promising approach under the condition of low voltage (0.8–1.2 V) and medium temperature. However, the rate of hydrogen production is slugged by poor anode kinetics, under an electrochemical condition that results from the collision of the coal particles with the anode surface. This paper reports a novel process that consists of two steps: the oxidation of the coal slurry by ferric ions(III) in a hydrothermal reactor at a temperature of 120–160 °C and the electro-oxidation of ferric ions(II) in the electrochemical cell to produce hydrogen. This technique circumvents the technical issues experienced in the conventional coal slurry electrolysis process by adopting a two-step process consisting of solid–liquid reactions instead of solid–solid reactions. This indirect oxidation process produced a current density of 120 mA/cm2 at room temperature and a voltage of 1 V, which is higher than the values reported in the conventional processes. An investigation of the oxidation mechanism was carried out via scanning electron microscopy, Fourier-transform infrared spectroscopy and elemental analysis. The results obtained showed that the oxidation of coal by ferric ions occurs from the surface to the inner parts of the coal particles in a stepwise manner. It was also revealed that the ferric ions in the media increased the active interfaces both of the coal particles and of the anode electrode. This explains the high hydrogen production rate obtained from this process. This novel discovery can pave the way for the commercialization of coal slurry electrolysis.

Hydrogen production activity of MoS2-ZnIn2S4 nanocomposite under visible light irradiation

In this manuscript, we report the synthesis of MoS2-ZnIn2S4 nanocomposite by using methods including hydrothermal and chemical aqueous method under low temperature. The prepared MoS2-ZnIn2S4 composite sample was characterized by X-ray powder diffraction(XRDfield emission scanning electron microscopy (FESEM). The photocatalytic activities for H2 production were investigated under the visible light of MoS2-ZnIn2S4 nanocomposite. The result indicates that H2 production rate of ZnIn2S4 increase by adding of MoS2 as co-catalyst and MoS2-ZnIn2S4 nanocomposite show higher rate of hydrogen production under. pure ZnIn2S4 sample shows a very low rate of H2 production activity (30 μ mol. g-1h−1) however MoS2/ZnIn2S4 composite shows approximately 3 times higher rate of H2 production activity (97.36 μ mol. g-1h−1. The synergistic combination of increased specific surface area, efficient electron hole pair separation, and amplified catalytic active sites is primarily responsible for the increased rate of H2 production activity. This work contributes a high potential of developing of low cost and low temperature or template free synthesised semiconductor for hydrogen production.

High hydrogen production rate from potassium borohydride hydrolysis with an efficient catalyst: CNT@Ru(0)

High hydrogen production rate from potassium borohydride hydrolysis with an efficient catalyst: CNT@Ru(0)

Effect of Natural Buffer on Biohydrogen Production

Hydrogen is the promising ideal energy carrier with no emission but water on its combustible in the next generation. Hydrogen production using biological methods is greener than other methods using fossil fuel. One of the major factors affecting the operation of biohydrogen production is pH level in bioreactors. Restrain of declining pH is expected to increase hydrogen production. Pretreatment is one key factor in successful biohydrogen fermentation using mixed microbes. This study aims to investigate the natural buffer effect on biohydrogen using hot compressed water pretreatment. This batch fermentation experiment was operated in a 110 mL glass reactor with 3.75 g/L glucose as substrate. Mixed culture was obtained from cow dung compost treated with hot compressed water pretreatment at 150 ºC, 0.5 MPa for 40 minutes. Fine dried eggshell powder and calcinated eggshell were added with 1 g/L, 3 g/L, and 5 g/L concentrations as buffer agents. The result showed that the addition of 1 g/L eggshell obtained the highest hydrogen production rate of 0.92 mol H2/mol glucose. Butyric acid and acetic acid are recognized as an indicator of hydrogen production and the Butyric/Acetic molar ratio over 2.6 as efficient biohydrogen fermentation. The highest B/A ratio in this experiment was 4.62 on 3g/L addition of eggshell powder.

Noble-metal-free p-n heterojunction of iron(III) hydroxide and graphitic carbon nitride for hydrogen evolution reaction

Realizing efficient photocatalytic hydrogen production of graphitic carbon nitride (g-C 3 N 4 ) in the absence of precious metals is one of the urgent research topics for industrial application. In this work, efficient p-n heterojunction of iron(III) hydroxide and graphitic carbon nitride (Fe(OH) 3 /g-C 3 N 4 ) for hydrogen production were successfully constructed using the electrostatic attraction self-assembly method. The Fe(OH) 3 /g-C 3 N 4 heterojunction could harvest more visible light, suppress recombination and boost transmission rate of the carriers. As expected, without participation of any precious metal, the highest hydrogen production rate (733 μmol h −1 g −1 ) was 51.2 folds higher than the unmodified g-C 3 N 4 at λ > 400 nm, which is superior to many previous results. Additionally, a possible reaction mechanism was proposed according to energy band analysis as well as the experimental photocatalytic activity results. To the energy and environmental studies fields, this work suggests a novel approach to design high efficiency photocatalysts using abundant and inexpensive metals instead of precious metals.

Effect of phosphating on NiAl-LDH layered double hydroxide form S-scheme heterojunction for photocatalytic hydrogen evolution

NiAl-LDH was completely phosphate to obtain Ni2P with strong adsorption characteristics, and a simple physical stirring method was used to fix Ni2P in the 3D layered double hydroxide NiAl-LDH layer to obtain a new type of Ni2P@NiAl-LDH (NNP) S-scheme heterojunction catalyst. The Ni2P obtained by phosphating process can provide 3D reaction sites for photoelectrons and absord photogenerated carriers to participate in the photocatalytic reaction. Moreover, the S-scheme interface heterojunction can directionally change the transfer path of electric charges and improve the effective utilization of electrons. The hydrogen evolution test results show that the hydrogen production of the composite material NNP-3 (Ni2P-15%@NiAl-LDH) within 5 h can reach 107.62 μmol (2152.4 μmolg−1 h−1), 17.27 times and 2.59 times of NiAl-LDH and Ni2P, respectively. And after 25 h hydrogen production cycle, the composite catalyst still has a high hydrogen production rate and showed strong stability. Optical tests show that the composite material Ni2P@NiAl-LDH (NNP) has a strong visible light capturing ability and can increase the absorption range of visible light. Photochemical tests show that the use of Ni2P to modify NiAl-LDH can reduce the overpotential of hydrogen evolution, accelerate the transfer of photoelectrons and improve the utilization of electrons. This research provides a new idea for improving the performance of NiAl-LDH using the phosphating process, and provides an effective method for NiAl-LDH to participate in the photocatalytic hydrogen evolution technology with high efficiency.

Unlocking the catalytic activities of 2H-phase Mo-based compounds via topological conversion reaction

Although 2H molybdenum disulfide (MoS2) layers are highly desirable for hydrogen evolution reaction (HER) owing to their high chemical stabilities and low cost, the inert basal plane and semiconducting nature severely hinder their practical applications. Here, the catalytic activities of 2H phase molybdenum-based compounds are unlocked via topological conversion reaction from Mo2GeC MAX phase to accordion-like molybdenum phosphosulphide. During the conversion reaction, phosphorus atoms can be implanted into the sandwich-like S-Mo-S planes and gradually substitute sulfur atoms, which are beneficial to optimize the electronic configuration and facilitate to absorb water molecules, unlocking the inert basal planes of 2H phase molybdenum-based compounds. The accordion-like molybdenum phosphosulphide exhibits high hydrogen production rates up to 288 mmol g−1 h−1 cm−2 at a high loading of 3 mg cm−2 and ultralong durability up to 35,000 cycles, satisfying the practical application for HER.

A new structure of Pt NF@Ni(OH)2/CdS heterojunction: Preparation, characterization and properties in photocatalytic hydrogen generation

A novel multi-heterostructured Pt NF@Ni(OH)2/CdS photocatalyst was applied in hydrogen generation from water splitting with (NH4)2SO3 acted as sacrifice. PtNi octahedral nano-particles (PtNi Octa) were synthesized by solvothermal method, and then etched with EDTA-2Na to obtain PtNi nanoframe (NF). The as-prepared PtNi NF was photodeposited on the surface of CdS in (NH4)2SO3 aqueous solution while the hydrogen photo-generation reaction took place. Since Ni ions are very active, easily combined with OH– to form Ni(OH)2, Pt NF@Ni(OH)2/CdS was formed gradually. The activity evaluation experiment reveals that Pt NF@Ni(OH)2/CdS exhibits a high hydrogen production rate of 44.05 mmol/h/g (QE = 58.89%, λ = 420 nm). The multi-heterostructure of Pt NF@Ni(OH)2/CdS photocatalyst was confirmed using XRD, TEM/EDS, XPS, PL, and ESR. The life spans of photo-induced electrons, in descending order, are Pt NF@Ni(OH)2/CdS > PtNi Octa/CdS > CdS, which explained the excellent photochemical and electrochemical properties of Pt NF@Ni(OH)2/CdS. This work provides a new strategy for photocatalyst designing.

Organic molecule embedded CdS nanocomposite for hydrogen generation from water: Effect of precursors’ concentrations

Organic molecule (Histidine) embedded cadmium sulfide (CdS) nanocomposites are prepared by the solvothermal method. CdS nanocomposite, prepared with 1:1 M ratio of S2− to Cd2+, shows the highest crystallinity and highest hydrogen production via water splitting. Optimization of Pt deposition indicates that 5.5 wt% of Pt deposition on CdS nanocomposite produces the highest amount of H2 gas. Moreover, the contents of histidine in CdS were changed from 0.0 to 2.5 mmol, and the result shows that CdS nanocomposite with 1 mmol of histidine has the highest rate of hydrogen production (21.35 mmol/g/h). This is one of the highest rates of hydrogen production from a single semiconductor photocatalyst system under visible light irradiation. These results indicate that organic molecules embedded CdS nanocomposites could be a promising photocatalyst for hydrogen production via water splitting.

Photocatalytic Properties of Amorphous N-Doped TiO2 Photocatalyst under Visible Light Irradiation

Amorphous TiO2 doped with N was characterized by its photocatalytic activity under visible light irradiation. The amorphous N-doped TiO2 was prepared by the sol-gel method through heat treatment at a low temperature. The photocatalyst showing activity in visible light despite heat treatment at low temperature can be applied to plastics and has excellent utility. The N-doped TiO2 appeared amorphous when heat-treated at 130 °C. It was converted into an anatase-type N-doped TiO2 when this was calcined at 500 °C. The photocatalyst showed photocatalytic activities in the photocatalytic decomposition of formaldehyde and methylene blue under visible light irradiation. The photocatalyst exhibited a higher rate of hydrogen production than that of TiO2 in photocatalytic decomposition of water under liquid-phase plasma irradiation. The bandgap of the amorphous N-doped TiO2 measured by investigation of optical properties was 2.4 eV. The lower bandgap induced the photocatalytic activities under visible light irradiation.