Triphenylphosphine ruthenium photocatalyst for hydrogen production

Abstract

The present disclosure discloses a photocatalyst for hydrogen production from water. The photocatalyst comprises triphenylphosphine ruthenium (RuP) complex. The RuP complex is a co-catalyst with graphitic carbon nitride. The present disclosure also discloses a method of synthesizing a photocatalyst for hydrogen production from water. The method comprises forming a suspension of graphitic carbon nitride; adding triphenylphosphine ruthenium complex (RuP) to the suspension; and drying the suspension to form dried graphitic carbon nitride integrated with RuP.

Claims

1. A photocatalyst for hydrogen production from water, the photocatalyst comprising: triphenylphosphine ruthenium (RuP) complex; wherein the RuP complex is a co-catalyst with graphitic carbon nitride, wherein the graphitic carbon nitride is combined with titanium carbide (Ti.sub.3C.sub.2) MXenes.

2. A photocatalyst as claimed in claim 1, wherein the graphitic carbon nitride is exfoliated graphitic carbon nitride.

3. A photocatalyst as claimed in claim 1, wherein the RuP complex is anchored on the graphitic carbon nitride.

4. A photocatalyst as claimed in claim 1, wherein the graphitic carbon nitride is graphitic carbon nitride nanosheets.

5. A photocatalyst as claimed in claim 1, wherein the titanium carbide MXenes comprise titanium dioxide (TiO.sub.2) nanodots.

6. A photocatalyst as claimed in claim 5, wherein the titanium dioxide nanodots are formed by etching.

7. A photocatalyst as claimed in claim 6, wherein the etching comprises treatment with hydrofluoric acid (HF).

8. A method of producing hydrogen from water, the method comprising: feeding water through a photoreactor, the photoreactor comprising a photocatalyst as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The manner in which the above-recited features of the present invention is understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present disclosure and are therefore not to be considered limiting of its scope, for the present disclosure may admit to other equally effective embodiments.

(2) FIG. 1 shows a method of synthesizing RuP loaded exfoliated graphitic carbon nitride (ECN) photocatalysts according to an embodiment of the present disclosure.

(3) FIG. 2 shows a method of synthesizing RuP loaded ECN and titanium carbide nanocomposite according to an embodiment of the present disclosure.

(4) FIG. 3 shows a photoreactor according to an embodiment of the present disclosure.

(5) FIGS. 4a-4d graphically show the effect of varying photocatalyst parameters on the yield of hydrogen according to an embodiment of the present disclosure.

(6) FIGS. 5a-5b show the effect of varying titanium carbide parameters on the yield of hydrogen according to an embodiment of the present disclosure.

(7) FIG. 6 shows the effect of various etching and irradiation time on the yield of hydrogen according to an embodiment of the present disclosure.

(8) FIG. 7 shows the effect of RuP and titanium carbide loading on the yield of hydrogen according to an embodiment of the present disclosure.

(9) FIG. 8 shows the effect of sacrificial reagent on the yield of hydrogen according to an embodiment of the present disclosure.

(10) FIG. 9 shows the effect of irradiation time and sacrificial reagent on the yield of hydrogen according to an embodiment of the present disclosure.

(11) FIG. 10 shows a diagram of a photoreactor according to an embodiment of the present disclosure.

(12) The foregoing and other objects, features and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of preferred embodiments, when read together with the accompanying drawings.

DETAILED DESCRIPTION

(13) The present disclosure relates to the field of photocatalysts and more particularly to triphenylphosphine ruthenium photocatalysts for hydrogen production.

(14) The principles of the present invention and their advantages are best understood by referring to FIG. 1 to FIG. 9. In the following detailed description of illustrative or exemplary embodiments of the disclosure, specific embodiments in which the disclosure may be practiced are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and equivalents thereof. References within the specification to one embodiment, an embodiment, embodiments, or one or more embodiments are intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure.

(15) FIG. 1 shows a method of synthesizing RuP loaded exfoliated graphitic carbon nitride (ECN) photocatalysts according to an embodiment of the present disclosure.

(16) Graphitic carbon nitride 104 is produced using a melamine 100 precursor. The melamine 100 precursor is thermally decomposed 102 at 550 C. for 2 hours to arrive at graphitic carbon nitride 104.

(17) For the synthesis of exfoliated graphitic carbon nitride (ECN) 110, a mixture of melamine and urea 106 is used. Melamine and urea 106 in equal amounts are mixed and placed in a ceramic crucible before being heated 108 to 550 C. for the duration of 2 hours. The gas produced by the decomposition of urea is used to exfoliate graphitic carbon nitride layers and produce defective graphitic carbon nitride with oxygen vacancies. The product obtained is grinded to a fine powder and is given name exfoliated graphitic carbon nitride (ECN).

(18) The source of ruthenium is tris (triphenylphosphine) ruthenium (ii) dichloride, named RuP 114. By using an impregnation technique, RuP 114 was added to ECN. To achieve uniform dispersion, 0.5 g of ECN powder is disseminated in 20 mL of methanol and agitated for 2 hours 118. The ECN suspension is then combined with RuP 114, dissolved in methanol 112 (RuP-methanol solution 116), and agitated 148 for a further 2 hours at room temperature. The final product is oven dried 120 at 100 C. and is given name RuP/ECN. FIG. 1 shows the schematic representation for the synthesis of RuP loaded ECN nanosheets 122.

(19) FIG. 2 shows a method of synthesizing RuP loaded ECN and titanium carbide nanocomposite according to an embodiment of the present disclosure.

(20) In the figure descriptions, like reference numerals denote like features. For example, feature 206 of FIG. 2 represents a like feature 106 of FIG. 1 (melamine and urea mixture, in this case).

(21) Similar to the process in FIG. 1, melamine and urea mixture 206 is exfoliated 208 to produce ECN 210.

(22) RuP 214 is dissolved in methanol 212 and agitated 248 with a solution of ECN 210 (which itself is ECN powder in methanol and agitated 218).

(23) The final product is oven dried 220 at 100 C. is given name RuP/ECN.

(24) Titanium aluminum carbide (Ti.sub.3AlC.sub.2) MAX 224 is etched 226 for 24 hours to arrive at multilayered titanium carbide (Ti.sub.3C.sub.2) MXenes 228. Ti.sub.3C.sub.2 MXenes are found to possess numerous characteristics, including great potential for charge carrier separation, higher surface hydrophilicity, mechanical, chemical, and thermal stability.

(25) Further etching 232 of Ti.sub.3C.sub.2 MXenes 228 for 48 additional hours, obtained Ti.sub.3C.sub.2 MXenes 234 with in-situ converted Ti.sub.3C.sub.2 to Ti.sub.3C.sub.2@TiO.sub.2.

(26) The multi-layered Ti.sub.3C.sub.2 with in-situ grown TiO.sub.2 nanoparticles are obtained through the hydrofluoric acid (HF) etching process.

(27) In embodiments of the present disclosure, the ECN/TiO.sub.2 Z-scheme heterojunction formation with the synergistic effect of RuP/Ti.sub.3C.sub.2 has been found to have a positive impact on maximizing solar hydrogen production. The reaction mechanism is proposed based on characterization results, in which the RuP role is to excite electrons to ECN, whereas Ti.sub.3C.sub.2 works as a sink to trap electrons from ECN/TiO.sub.2, enabling significantly enhanced charge carrier separation. The higher photocatalytic activity is because of promoted reaction kinetics and proficient charge carrier separation in binary cocatalysts with in-situ grown nanoparticles of TiO.sub.2 230, enabling higher hydrogen production. Thus, dual function composite photocatalysts according to an embodiment of the present disclosure accelerate oxidation and reduction reactions through a multi-step process.

(28) The RuP-embedded Ti.sub.3C.sub.2@TiO.sub.2/ECN nanocomposite is synthesized through an impregnation approach. Initially, Ti.sub.3C.sub.2 234 is dispersed in a methanol solution, and then RuP/ECN is dispersed in a methanol solution and is added 226 to get good interface interaction. The mixture was agitated for an additional two hours after adding the ruthenium precursor, which had been dissolved in methanol. After drying at 100 C. (overnight), the product is denoted as RuP loaded Ti.sub.3C.sub.2@TiO.sub.2/ECN heterojunction.

(29) FIG. 3 shows a photoreactor according to an embodiment of the present disclosure. The photoreactor comprises a solution containing photocatalyst 350 according to an embodiment of the present disclosure.

(30) Transmitted light 303 passes into the photoreactor to initiate the reaction process. Typically, some light 301 is reflected off the reactor surface.

(31) In embodiments, the photoreactor is a flat wall photoreactor. In embodiments, the photoreactor is an annular photoreactor.

(32) The photoreactor of FIG. 3 is figurative and does not show all of the conventional details of typical photoreactors.

(33) In embodiments of the present disclosure, there is provided a dye sensitized solar cell comprising a photocatalyst according to embodiments of the present disclosure.

(34) To validate the method, EDX mapping was used to further explore the distribution of the elements in the RuP loaded ECN samples. In mapping photos, the consistent and excellent distribution of RuP over ECN was readily discernible, and confirmed the existence of Ru, C, N, and O components in the RuP/ECN composite. These findings support the effective synthesis of RuP/ECN composite and would be useful for efficient charge carrier separation with improved light distribution.

(35) TEM analysis was conducted to further investigate the morphology of the ECN and RuP-loaded ECN samples, and the results show morphology of ECN. It was observed that ECN has a 2D layered structure, in which graphitic carbon nitride sheets are exfoliated, giving obvious gaps between the layers. The morphology of RuP/ECM composite reveals an exfoliated structure of ECN, where each layer is separated from the others, providing openings for light to penetrate. The analysis shows that RuP particles are entirely distributed over the ECN surface to provide good interface interaction between both the materials. High-resolution TEM (HRTEM) images reveal an amorphous structure of ECN with the presence of RuP. The presence of RuP was clearly observed in high resolution images which further confirmed the successful fabrication of the RuP/ECN composite.

(36) Live fast Fourier transform (FFT) images were used to calculate lattice spacing and their values were found to be 0.32 nm, which corresponds to graphitic carbon nitride.

(37) All these findings demonstrate that RuP/ECN nanotextures can successfully be fabricated according to embodiments of the present disclosure, and that they would be useful for the efficient separation of photoinduced carriers to maximize photocatalytic performance.

(38) Experimentation: RuP/ECN

(39) Photocatalytic water splitting was carried out using a slurry photoreactor system in which specific amount of catalyst (100 mg) was uniformly dispersed using magnetic stirrer. Methanol (5 vol %) was utilized as the sacrificial reagent for the photocatalyst screening. When exposed to low power visible light of 35 W with an intensity of 20 mW/cm2, performance assessment of pure and modified photocatalysts was compared in relation to hydrogen production.

(40) FIGS. 4a-4d graphically show the effect of varying photocatalyst parameters on the yield of hydrogen according to an embodiment of the present disclosure.

(41) The morphological effect of graphitic carbon nitride (CN) and graphitic carbon nitride nanosheets (ECN) for photocatalytic hydrogen generation was first calculated. Photocatalytic hydrogen development over CN and ECN samples at various irradiation time is presented in FIG. 4a. Using CN, the yield of hydrogen of 25 umole was achieved after 3 h of irradiation time 407, whereas ECN produces 24% more hydrogen yield (31 umole 405) compared to CN photocatalyst. The greatest hydrogen yield using ECN was 103 umol g.sup.1h.sup.1, which is 1.24 times more than utilizing bulk CN nanosheets. This demonstrates that the ECN structure has more advantages for producing a larger yield of hydrogen. Evidently, less charge recombination and higher BET surface area allowed for greater hydrogen evolution under visible light. The performance of ECN was further compared with the standard TiO.sub.2 (P25), and the results are shown in FIG. 4b. Initially, lower amount of hydrogen was produced over the TiO.sub.2, however, it was significantly higher than ECN over the irradiation time, with the TiO.sub.2 hydrogen yield 409 being almost triple that of the ECN 411 by 120 minutes. As the TiO.sub.2 (P25) has the nanoparticles (<21 nm) with mesoporous structure and higher surface area, thus, it was more promising to enhance hydrogen production. The performance of pure CN can be made more efficient when modified with some types of metals and other cocatalysts. Comparatively, pure TiO.sub.2 is more efficient than pristine CN due to more charge recombination in CN.

(42) FIG. 4c shows the photocatalytic hydrogen generation over several RuP loaded ECN samples. Compared to CN and ECN samples, hydrogen yield was significantly enhanced with RuP loading. Using 2% RuP, hydrogen yield was raised to 140 umol with the ECN sample. However, a significant quantity of hydrogen was produced when ECN was loaded with optimized 3% RuP loading 413 (176 umol), which was 6.1 and 8.6 times more than utilizing pristine ECN sample, respectively. 5% RuP loading is represented by the line 415, which is slightly lower than the 3% loading 413. Due to increased electron generation over the ECN under visible light irradiation because of RuP photosensitizer, the hydrogen yield over RuP/ECN was clearly improved. However, the yield of hydrogen is negatively impacted by loading over 4 wt % RuP loading. The increasing RuP loading increased the blackish color of ECN, which lowers light penetration into the slurry system.

(43) In embodiments of the present disclosure, the loading of RuP is between 2% and 5%.

(44) The photocatalytic performance of RuP/ECN was further investigated using 5 vol % concentrations of methanol, ethanol, and glycerol as sacrificial reagents. FIG. 4d illustrates the performance comparison of these three reagents for photocatalytic hydrogen generation. While pure water generated 48 umol of hydrogen over a 3RuP/ECN (the 3 representing 3% loading) photocatalyst after 4 h of irradiation time, the addition of sacrificial reagents such as glycerol, methanol, and ethanol improved the hydrogen production. The use of glycerol resulted in a hydrogen production of 69.5 umol, a 1.45-fold improvement over using water only. Methanol 417 has produced the maximum hydrogen yield of 176 umol, which is 1.23, 2.53, and 3.67 times greater than the yields obtained with ethanol 419, glycerol, and pure water, respectively.

(45) The presence of a sacrificial reagent can increase the number of protons (H+) produced during the water splitting process. Therefore, in addition to generating the protons and electrons required for hydrogen reduction, the sacrificial reagent also traps holes to prevent the recombination of charges. Sacrificial reagent, in general, traps holes and is useful for producing electrons, resulting in an abundance of protons (H+) and electrons (e) for the reduction reaction to produce hydrogen. As a result, lower hydrogen yield with water can be attributed to more recombination of electron-hole pairs rather and lower proton (H+) generation.

(46) Experimentation: RuP-embedded Ti.sub.3C.sub.2@TiO.sub.2/ECN

(47) Field emission scanning electron microscopy (FESEM) was used to explore further the surface morphology and composition data of Ti.sub.3AlC.sub.2, Ti.sub.3C.sub.2, ECN, and their composites.

(48) Stacks of sheets are visible in the compact block structure of Ti.sub.3AlC.sub.2. Ti.sub.3C.sub.2 MXene was produced in a 2D layered structure after being etched with hydrofluoric acid (HF) for 24 h, as illustrated in FIG. 2. The Ti.sub.3C.sub.2 presents an accordion-like structure, in which 2D nanosheets are loosely stacked to give multilayered nanotexture. As a result, Ti.sub.3C.sub.2 may be seen to have a multilayer structure with a smooth surface and very few particles of TiO.sub.2 produced on the layered surface.

(49) When the etching duration is extended to 48 hours, more TiO.sub.2 nanoparticles are produced. This is due to the conversion of Ti.sub.3C.sub.2 MXene to TiO.sub.2 at the prolonged etching time, and it can work as a semiconductor to have photoinduced charge carriers. This can provide more active sites and surface functional groups with TiO.sub.2 nanoparticles (NPs) to work as the binder to make it easier to interact with other materials and reactants.

(50) Very small-size TiO.sub.2 NPs embedded over 2D layered stricture were achieved without destroying the original structure of MXene according to embodiments of the present disclosure.

(51) Furthermore, when the etching time was increased to 96 hours, the amount of TiO.sub.2 was decreased compared to its production after 48 hours. This was probably due to detaching TiO.sub.2 NPs from the Ti.sub.3C.sub.2 surface after a prolonged stirring time. However, it was observed that after increasing etching time, layered gaps between Ti.sub.3C.sub.2 sheets were increased, and TiO.sub.2 NPs were also grown at the surface of the Ti.sub.3C.sub.2 sheets within the galleries. This was possibly due to converting more Ti.sub.3C.sub.2 MXene to TiO.sub.2, sheets becoming thin, and their gaps increased over increasing etching time.

(52) FIGS. 5a-5b show the effect of varying titanium carbide parameters on the yield of hydrogen according to an embodiment of the present disclosure.

(53) The performance of the photocatalysts was tested in a slurry photoreactor system, in which 5-vol % sacrificial reagent (methanol) and 100 mg photocatalyst were used. The effect of etching time on the performance of Ti.sub.3C.sub.2 was investigated. For this purpose, Ti.sub.3C.sub.2 etched at three different times: 24, 48 and 96 hours, were tested for photocatalytic hydrogen production while keeping all other reaction parameters identical. As shown in FIG. 5a, HER (photocatalytic hydrogen evolution) reaction for hydrogen production was different at various durations of 24, 48, and 96 hours. Even though Ti.sub.3C.sub.2 has metallic characteristics and would not be expected to produce hydrogen, its photoactivity can be attributed to the photoactivation of TiO.sub.2 NPs grown over its surface, which results in the formation of charge carriers when exposed to light irradiation.

(54) More significantly, during etching for 24 hours, 125 umol g.sup.1 h.sup.1 of hydrogen was produced; this value increased to 182.5 umol g.sup.1 h.sup.1 when etching was conducted for 48 hours. The higher hydrogen production with increasing etching time was due to more formation of TiO.sub.2 NPs over the Ti.sub.3C.sub.2 surface, which works as the semiconductor to produce photoinduced electrons, whereas Ti.sub.3C.sub.2 works as a sink to trap electrons for the reduction reaction to produce hydrogen. Due to Ti.sub.3C.sub.2 metallic properties, its role in the generation of hydrogen can be attributed to the trapping of electrons from TiO.sub.2 CB that was developed on its surface during the HF etching process. However, a decline in hydrogen production was observed when etching time was increased above 48 hours. This was likely due to excessive production of TiO.sub.2 NPs, but they were detached from the Ti.sub.3C.sub.2 surface due to continuous stirring and during the washing process. These results are in good agreement with the characterization results supported by XRD, SEM, RAMAN and others. Thus, 48 h is the optimized etching time, giving the highest photocatalytic activity for hydrogen production.

(55) In embodiments of the present disclosure, the etching time is between 24 and 72 hours. In embodiments of the present disclosure, the etching time is between 36 and 60 hours.

(56) FIG. 5b illustrates the photocatalytic activity of Ti.sub.3C.sub.2/ECN composites with various loading amounts of Ti.sub.3C.sub.2, synthesized after 48 hours of etching time. Using pure ECN, hydrogen evolution was not substantial, perhaps because charge carriers had a shorter lifetime. More significantly, during etching for 24 hours, 125 umol g.sup.1 h.sup.1 of hydrogen was produced; this value increased to 182.5 umol g.sup.1 h.sup.1 when etching was conducted for 48 hours.

(57) The highest hydrogen evolution rate of 310 umol g.sup.1 h.sup.1 was obtained over 10 wt % Ti.sub.3C.sub.2 loading with ECN 423, which is 1.56, 1.55 and 2.34 times higher than it was produced using 15% Ti.sub.3C.sub.2, 5% Ti.sub.3C.sub.2 and pure ECN samples, respectively.

(58) Due to the metallic character of Ti.sub.3C.sub.2, a faster charge carrier separation over the ECN would be achieved, enabling an increase HER reaction for hydrogen production.

(59) FIG. 6 shows the effect of various etching and irradiation time on the yield of hydrogen according to an embodiment of the present disclosure.

(60) Further research was done on how irradiation time and etching time affected the performance of optimized Ti.sub.3C.sub.2 with ECN, and the results are shown in FIG. 6. Initially, after one hour of irradiation time, the highest hydrogen yield was obtained using Ti.sub.3C.sub.2 produced after 96 hours of etching time. However, over the irradiation time, its performance was dropped. These results are expected due to the exfoliated Ti.sub.3C.sub.2 nanosheets with TiO.sub.2 NPs, enabling more light absorption and generation of charge carriers. However, due to less availability of TiO.sub.2 NPs and their dispatched during continuous stirring, charge separation was lower compared to Ti.sub.3C.sub.2 synthesized after 48 hours of irradiation time 425. More importantly, photocatalytic hydrogen production results resembled the previously discussed pristine Ti.sub.3C.sub.2 samples. This shows that no matter how much TiO.sub.2 is grown, it acts as an electron mediator, moving electrons from ECN towards Ti.sub.3C.sub.2 nanosheets to increase the reduction reaction to produce more hydrogen.

(61) FIG. 7 shows the effect of RuP and titanium carbide loading on the yield of hydrogen according to an embodiment of the present disclosure.

(62) The synergistic effect of RuP and Ti.sub.3C.sub.2@TiO.sub.2 with ECN was further explored using optimized 3 wt % RuP and 10 wt % Ti.sub.3C.sub.2 synthesized after 48 hours of etching time, and the results are shown in FIG. 7. In general, production of hydrogen was continuous with Ti.sub.3C.sub.2/ECN composite over the entire irradiation time; however, using RuP-based composite 427, photocatalytic activity declined after the third hour of reaction time. Using pure ECN, 305 umol g.sup.1 of hydrogen was produced, which was increased to 1760 and 1185 umol g.sup.1 when coupled with RuP and Ti.sub.3C.sub.2 MXene respectively after 4 hours. The maximum hydrogen production of 5315 umol g.sup.1 was obtained using RuP-Ti.sub.3C.sub.2/ECN composite 427 samples. This amount of hydrogen produced was 2.91, 5.16 and 18.01-fold more than using RuP/ECN, Ti.sub.3C.sub.2/ECN and ECN samples, respectively.

(63) Due to the synergistic interaction between RuP and Ti.sub.3C.sub.2 MXene and ECN, which allowed excited electrons to be transported to the CB of ECN by RuP and effectively trapped by Ti.sub.3C.sub.2, the photocatalytic activity for the formation of hydrogen was significantly increased. Furthermore, quantum yield (QY) of the pure and the composite was calculated based on production rate and photon flux utilization. Using RuP-Ti.sub.3C.sub.2/ECN, QY of 5.18% was obtained for hydrogen production, which was 2.91, 5.16 and 18.02 times higher than using RuP/ECN, Ti.sub.3C.sub.2/ECN and pure ECN samples, respectively.

(64) FIG. 8 shows the effect of sacrificial reagent on the yield of hydrogen according to an embodiment of the present disclosure.

(65) The performance comparison of Ti.sub.3C.sub.2/ECN and RuP-Ti.sub.3C.sub.2/ECN composites was further investigated using other sacrificial reagents; their results are presented in FIG. 8. In both cases, 5 vol % of methanol, glycerol and ethanol sacrificial reagents were used to examine the photocatalytic activity further. Using only water, 360 and 325 umol g.sup.1 hydrogen yields were produced with RuP-Ti.sub.3C/ECN and Ti.sub.3C/ECN, respectively, which was only 1.08 times higher when RuP was loaded to Ti.sub.3C/ECN composite. Using methanol as the sacrificial reagent, the performance of RuP-Ti.sub.3C.sub.2/ECN composite 429 was 7-fold higher than hydrogen produced over Ti.sub.3C.sub.2/ECN photocatalyst 431. Sacrificial reagents, significantly boost hydrogen yield, and their performance was higher in order methanol >ethanol >glycerol using both composite materials. The amount of hydrogen produced with methanol and RuP-Ti.sub.3C.sub.2/ECN composite was 12.1 folds higher than using only water. When ethanol was used, 1325 umol g.sup.1 of hydrogen was produced with RuP-Ti.sub.3C.sub.2/ECN composite, a 3.68-fold increase than when water alone was used and 3.23 times more when only Ti.sub.3C.sub.2/ECN was employed. Among the three sacrificial reagents, the lowest hydrogen amount was produced when glycerol was used with both the composite materials, whereas the performance of RuP-Ti.sub.3C.sub.2/ECN composite was 3.49-fold higher than using composite without RuP.

(66) FIG. 9 shows the effect of irradiation time and sacrificial reagent on the yield of hydrogen according to an embodiment of the present disclosure.

(67) Further research on the impact of irradiation time on the performance of the RuP-Ti.sub.3C.sub.2/ECN composite with water, methanol, and ethanol as sacrificial reagents is shown in FIG. 9. Using water, continuous hydrogen production was obtained; however, with ethanol and methanol, it slightly declined after 3 hours of irradiation time. This could be because the reaction temperature is rising, which prevents reactants from adhering to the catalyst's surface, or it might be because methanol is consumed during photocatalysis. Comparatively, the highest hydrogen yield was produced with methanol as the sacrificial reagent over RuP-Ti.sub.3C.sub.2/ECN composite, which was 3.27, 3.46 and 12.1 folds higher than using ethanol, glycerol and water, respectively.

(68) RuP-Ti.sub.3C.sub.2/ECN composite according to embodiments of the present disclosure can be synthesized and utilized for photocatalytic hydrogen evolution. Compared to bulk CN, ECN was more efficient due to its layered structure with efficient charge separation. The performance of ECN was enhanced when coupled with Ti.sub.3C.sub.2 and RuP to construct Ti.sub.3C.sub.2/ECN, RuP/ECN and RuP-Ti.sub.3C.sub.2/ECN composites. Comparatively, TiO.sub.2 NPs embedded over Ti.sub.3C.sub.2 multilayered nanotexture after 48 hours of etching time were most efficient in promoting photocatalytic hydrogen evolution. Due to the minimal charge carrier recombination effect and efficient separation provided by the presence of highly conductive nanosheets, Ti.sub.3C.sub.2 produces significantly more hydrogen when mixed with ECN. On the other hand, RuP enables the injection of excited electrons to the CB of ECN, resulting in improved hydrogen production. The synergistic effect of RuP/Ti.sub.3C.sub.2 with ECN significantly enhances hydrogen production, whereas in embodiments, the highest yield of 5315 umol g.sup.1 is produced after 3 hours of reaction time. The composite is also stable to produce hydrogen in multiple cycles.

(69) FIG. 10 shows a diagram of a photoreactor according to an embodiment of the present disclosure.

(70) The photoreactor is an externally reflected photoreactor.

(71) The photoreactor consists of a cylindrical shell 514 which contains catalysts 504 and water solution to carry the photocatalysis reaction. A lamp 502 is placed inside the inner shell 516, which has a light intensity of 20 mW c.sup.2 and wavelength similar to that of solar energy. To maximize the concentration of light inside the slurry system, the outer cylindrical vessel 514 is covered with a parabolic reflector 506. Typically, 100 mL of water solution containing 5 percent methanol and the precise amount of photocatalyst 504 (100 mg) is added inside the reactor chamber. To dissipate the heat generated by the bulb, a water circulation system 510 is attached to the cylinder. The water circulation system 510 may be a magnetic stirrer. A parabolic reflector 506 is connected to the outside of the glass cylinder to reflect the light irradiations from the lamp 502, which allows for a systematic comparison of the photocatalytic system's performance with and without the reflector. Nitrogen 508 flows continuously, and after every hour, the byproducts are collected using gas sampling bags and are analyzed using gas analyzer 512 and gas chromatography (GC-TCD).

(72) It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. The disclosures and the description herein are intended to be illustrative and are not in any sense limiting the present disclosure, defined in scope by the following claims.

(73) Many changes, modifications, variations and other uses and applications of the present disclosure will become apparent to those skilled in the art after considering this specification and the accompanying drawings, which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications, which do not depart from the spirit and scope of the present disclosure, are deemed to be covered by the invention, which is to be limited only by the claims which follow.