In-situ construction method of in-vivo capacitance function material and application of in-vivo capacitance function material in hydrogen production

Abstract

The invention discloses an in-situ construction method of an in-vivo capacitance functional material and application of the in-vivo capacitance functional material in hydrogen production, and belongs to the field of catalysis. According to the method, the enzyme catalysis capability of dissimilatory metal reducing bacteria S.oneidensis MR-1 is utilized, and the in-vivo capacitance function material S.oneidensis MR-1-CdS / RGO is constructed in situ. The living body capacitance function material can be well used as a light-dark alternating electronic converter, and can realize the capacitance performance on the time scale, namely hydrogen is produced and redundant electrons are stored during illumination, and the electrons are released to continuously produce hydrogen after a light source is removed. Researches find that the capacitive performance benefits from a CdS / RGO material, an extracellular polymer (EPS) secreted by bacteria and an intracellular NAD < + > / NADH redox couple of bacteria. The living body capacitance functional material constructed by the method can realize illumination hydrogen production, and hydrogen can be continuously produced after a light source is removed.

Description

Technical Field

[0001] The invention belongs to the field of catalysis, and in particular relates to an in-situ construction method of a living capacitor functional material and an application thereof in hydrogen production. Background Art

[0002] In the field of catalysis, the use of purely chemically synthesized semiconductor materials such as CdS or CdS / RGO for photocatalytic hydrogen production will produce a large amount of pollutants and easily cause secondary pollution. The use of biological-material coupling systems for photocatalytic hydrogen production is a relatively environmentally friendly and sustainable method developed in recent years. The reported biological-material coupling systems for photocatalytic hydrogen production include two systems: chemical synthesis of semiconductors followed by addition and biological in situ construction. The former still involves the generation of pollutants and the problem of easy secondary pollution.

[0003] The microorganisms involved in the biological in situ construction of the biological-material coupling system can synthesize semiconductors with photocatalytic activity under mild conditions. Considering the photosensitivity of semiconductor materials, the large specific surface area of ​​carbon materials and the catalytic function of microbial enzymes, the microorganisms of the present invention synthesize CdS / RGO / SW in situ, wherein the carbon material is the link between the semiconductor material and the organism, and the living functional material has capacitive properties. That is, hydrogen is produced and electrons are stored during illumination, and electrons are released and hydrogen is continuously produced after the light source is removed. Compared with the reported continuous illumination conditions, the living capacitive functional material S. oneidensis MR-1-CdS / RGO in this study has higher biological activity, stronger hydrogen production rate and sustainability under light-dark alternation conditions, better conforms to the changes in daily sunlight alternation between day and night, and has the potential for practical application. And compared with the reported mixing of chemically synthesized materials and microorganisms, the present invention has stronger performance in photocatalysis and capacitive hydrogen production. Summary of the invention

[0004] In view of this, the present invention provides an in-situ construction method of a living capacitor functional material and its application in hydrogen production. The present invention utilizes the reduction ability of microorganisms to synthesize the photosensitizer CdS NPs in situ and construct a living capacitor functional material S.oneidensis MR-1-CdS / RGO. The living capacitor functional material has the ability to produce hydrogen and store electrons when illuminated, and release electrons in the dark to continuously produce hydrogen, and its capacitance performance comes from the solid phase material CdS / RGO, the extracellular polymer EPS and the intracellular redox couple NAD + / NADH and other substances.

[0005] The in-situ construction method of the living capacitor functional material of the present invention comprises the following steps:

[0006] Step 1: Cultivate the dissimilatory metal-reducing bacteria in LB medium until the early stage of the plateau;

[0007] Step 2: The dissimilatory metal-reducing bacteria cultured to the early stage of the platform in step 1 are resuspended in a culture medium containing thiosulfate for anaerobically cultured, and then Cd(II)-EDTA and graphene oxide GO are added to the culture system. Anaerobically culture is performed until Cd(II) is completely converted into CdS NPs semiconductors, thereby constructing a living capacitor functional material S. oneidensis MR-1-CdS / RGO.

[0008] Furthermore, in step 1, the dissimilatory metal-reducing bacteria stored at -80°C were streaked on a plate, cultured aerobically for 48 h, and then single colonies were selected in LB liquid culture medium, cultured aerobically for 12 h, and then transferred to fresh LB liquid culture medium at a ratio of 1:10, and continued to be cultured aerobically for 12 h.

[0009] The dissimilatory metal-reducing bacteria is the wild-type WT strain of S. oneidensis MR-1.

[0010] In step 2, the culture medium containing thiosulfate is based on LB liquid culture medium, to which thiosulfate is added, the concentration of thiosulfate is between 0.1-5 mM, and the thiosulfate is sodium thiosulfate.

[0011] In step 2, the concentration of Cd(II)-EDTA is between 0.1-5 mM and is the same as the concentration of the added thiosulfate.

[0012] In step 2, the concentration of graphene oxide GO in the culture system is between 10-500 mg / L.

[0013] Furthermore, in step 2, the anaerobic culture time with thiosulfate is 6-12 h; the culture time after adding Cd(II)-EDTA and graphene oxide GO is 6-12 h.

[0014] The concentrations of sodium thiosulfate, Cd(II)-EDTA and graphene oxide GO affect the performance, especially the bacterial activity and enzyme function. After optimization, the present invention uses 0.3mM sodium thiosulfate, 0.3mM Cd(II)-EDTA and 50mg / L graphene oxide GO.

[0015] In step 2, the anaerobic culture is achieved by exposing the culture medium to nitrogen for 30 minutes.

[0016] Application of the living capacitor functional material of the present invention in hydrogen production.

[0017] Specifically, the living capacitor functional material S. oneidensis MR-1-CdS / RGO is transferred into a liquid inorganic salt culture medium that has been fully aerated with nitrogen, and catalytic hydrogen production is carried out under light or light-dark cycle conditions.

[0018] When catalyzing hydrogen production under light-dark cycle conditions, the light-dark time ratio is 1:1.

[0019] Furthermore, during the light-dark cycle, the reaction lasted for 2 h in the light and 2 h in the dark.

[0020] In the present invention, a xenon lamp was used as the light source in the experiment, and the light intensity was 20 mW / cm 2 .

[0021] The components of the liquid inorganic salt culture medium are: NaCl 5-6 g / L, NH4Cl 1-2 g / L, KCl 0.05-0.1 g / L, HEPES 11-12 g / L, β-sodium glycerophosphate 0.5-0.8 g / L, sodium lactate 15-25 mM, trace elements 1 mL trace element mother solution / L culture medium, and ascorbic acid 9-11 mM.

[0022] In the following examples, the composition of the liquid inorganic salt culture medium is shown in Table 1 below (the final pH is adjusted to 6.7).

[0023]

[0024] The formula composition of the trace element mother solution is shown in Table 2.

[0025]

[0026] During the experiment of the present invention, the following control groups were set up for comparison: a living capacitor functional material S. oneidensis MR-1-CdS / RGO dark group and a pure material CdS / RGO control group that inhibits microbial activity.

[0027] Although the photocatalytic hydrogen production using the assembly of microorganisms and semiconductor materials has been reported, the continuous exposure to light causes high toxicity to the microorganisms, is unsustainable, and does not conform to the actual law that sunlight alternates between light and dark cycles.

[0028] Therefore, the present invention biologically in situ self-assembles a living capacitor functional material S. oneidensis MR-1-CdS / RGO, utilizes the biological reduction ability of S. oneidensis MR-1, in situ constructs a living material contacted by microorganisms, CdS NPs and reduced graphene oxide RGO, and uses it to produce hydrogen in a light-dark cycle.

[0029] Compared with the reported hydrogen production methods, the present invention has the following advantages:

[0030] The present invention can recycle heavy metal ions while synthesizing sulfide semiconductor materials in situ in an environmentally friendly and mild microbial enzyme catalytic manner. It does not involve toxic solvents and is simple to operate and pollution-free. Compared with the reported continuous illumination conditions, the living capacitor functional material S. oneidensis MR-1-CdS / RGO in this study has higher biological activity, stronger hydrogen production rate and sustainability under light-dark alternation conditions, better conforms to the daily changes in sunlight day and night, and has the potential for practical application. Compared with the reported mixture of chemically synthesized materials and microorganisms, the present invention has stronger performance in photocatalysis and capacitive hydrogen production. The living capacitor functional material S. oneidensis MR-1-CdS / RGO constructed in situ by the present invention has the performance of producing hydrogen and storing electrons under illumination, and releasing electrons in the dark to continuously produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 OD after transfer culture of the living capacitor functional material S. oneidensisMR-1-CdS / RGO constructed under different precursor concentration conditions in Example 1 600 Value (reflecting microbial activity).

[0032] Figure 2 The scanning electron microscope (SEM) (A) of the living capacitor functional material S. oneidensis MR-1-CdS / RGO in Example 1 and the statistical results of the biosynthesized CdS particle size (B) are shown.

[0033] Figure 3 The scanning electron microscope (SEM) (A) and corresponding mapping (B) results of the living capacitor functional material S. oneidensis MR-1-CdS / RGO in Example 1.

[0034] Figure 4 (A) and (B) are the Raman spectra (Raman) and X-ray diffraction (XRD) results of various materials purified in Example 1, respectively; Figure 4 (C) is the photoluminescence spectrum (PL) results of CdS / RGO / SW, CdS / SW, RGO / SW, CdS / RGO and CdS in Example 1.

[0035] Figure 5 The hydrogen production of each living material and inactivated group in Example 2 changes with time under pure darkness (A) and light-dark cycle (B); Figure 5 (CD) Correspondence Figure 5 (AB) Photocatalytic, capacitive and dark hydrogen production rates of each living material and inactivated group.

[0036] Figure 6(A) is the intracellular NADH / NAD of bacteria in the living capacitor functional material S. oneidensis MR-1-CdS / RGO system under the light-dark cycle conditions of Example 3 + changes; Figure 6 (BD) are the cyclic voltammetry (CV) curves and statistical capacitance results of different purified materials; Figure 6 (E) CV results of the inactivated material CdS / RGO at different scanning speeds; Figure 6 (F) is the constant current charge-discharge (GCD) curve of the inactivated material CdS / RGO at different scanning currents; Figure 6 (G) EAC / EDC results of different purified materials; Figure 6 (H) UV-vis results of different living material groups; Figure 6 (I) is the EAC / EDC result of EPS.

[0037] Figure 7 (A) is the OD after transfer culture of the living capacitor functional material S. oneidensis MR-1-CdS / RGO using different construction methods (biological in situ method or chemical addition method) in comparative example 1 600 value (reflecting microbial activity); Figure 7 (B) The hydrogen production per unit liquid volume of the light-dark alternating and continuous illumination groups after 96 hours of reaction.

[0038] Figure 8 The SEM (A) and CdS particle size statistics (B) of the chemically synthesized material CdS / RGO in Comparative Example 2 are shown in FIG. Figure 8 (C)Figure shows the XRD results of CdS / RGO.

[0039] Fig. 9 The hydrogen production of S. oneidensis MR-1-CdS / RGO, a capacitor functional material constructed by biological in situ method and chemical addition method, changes over time in pure darkness (A) or light-dark cycle (B); Fig. 9 (C) Correspondence Fig. 9 (AB) Photocatalytic, capacitive and dark hydrogen production rates of each group. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below. The following content is only an example and explanation of the concept of the present invention. The technicians in the relevant technical field make various modifications or supplements to the specific implementation cases described or replace them with similar methods. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0041] The present invention utilizes a microbial enzyme system to construct in situ a living capacitor functional material S.oneidensis MR-1-CdS / RGO, which can realize hydrogen production and storage of photoelectrons during illumination, and release the stored photoelectrons in darkness to continuously produce hydrogen. Compared with most existing chemical methods for hydrogen production, the present invention has mild reaction conditions and is environmentally friendly; compared with most existing photocatalytic biological-material coupling systems for hydrogen production, the present invention has high microbial activity, better photocatalytic and capacitor sustainable hydrogen production performance, and complies with the law of daily solar light-dark alternation.

[0042] The present invention uses a commercially available wild-type strain (WT) of dissimilatory metal-reducing bacteria S. oneidensis MR-1, and its commercial serial number information is as follows: Shewanella oneidensis ATCC 700550, MR-1; Taxonomy ID: 211586).

[0043] The following further describes the in-situ construction method of a living capacitor functional material provided by the present invention and its application in hydrogen production.

[0044] Example 1: In situ construction of living capacitor functional material S. oneidensis MR-1-CdS / RGO by Shewanella oneidensis MR-1

[0045] (1) Construction of the living capacitor functional material S. oneidensis MR-1-CdS / RGO: The S. oneidensis MR-1 strain (wild type) cultured in LB medium to the early stage of the platform was resuspended in fresh LB anaerobic medium (initial OD 600 =0.2, nitrogen was exposed for 30 min and sealed). A certain concentration of sodium thiosulfate was added, and after anaerobic culture for 6 h, corresponding concentrations of Cd(II)-EDTA and graphene oxide GO were added, and anaerobic culture was continued for 12 h to obtain the living capacitor functional material S. oneidensis MR-1-CdS / RGO. The concentrations of the precursors such as sodium thiosulfate, Cd(II)-EDTA and graphene oxide GO added are shown in Table 3.

[0046]

[0047] (2) Optimization of conditions for the living capacitor functional material S. oneidensis MR-1-CdS / RGO: The groups with different precursor concentrations in (1) were transferred and cultured at a ratio of 1:100. The culture conditions were 200 rpm, 30°C, and 12 h. The OD600 absorbance was measured to determine the bacterial activity. Figure 1It is known that the optimized experimental conditions are the addition of 0.3 mM sodium thiosulfate, 0.3 mM Cd(II)-EDTA and 50 mg / L GO.

[0048] (3) Recovery of the living capacitor functional material S. oneidensis MR-1-CdS / RGO: The living capacitor functional material S. oneidensis MR-1-CdS / RGO optimized and constructed in (2) was collected by centrifugation and washed, then vacuum-freeze-dried and ground into powder for subsequent characterization such as XRD.

[0049] (4) Performance index tests were performed on the in-situ constructed living capacitor functional material S. oneidensis MR-1-CdS / RGO of this embodiment:

[0050] Scanning electron microscope (SEM) sample preparation: The living carbonaceous semiconductor material optimized in (2) was washed three times with PB buffer (pH = 7.2) by centrifugation, fixed with 2.5% glutaraldehyde, and kept at 4°C overnight. The next day, it was washed three times with PB buffer (PH = 7.2) by centrifugation, and then dehydrated with different concentrations of ethanol gradient (30%, 50%, 70%, 80%, 90%, 93%, 95%, 97%, 100%), and the living carbonaceous semiconductor material was soaked for 20 minutes at each concentration. Finally, the dehydrated living carbonaceous semiconductor material was dropped on a silicon wafer and observed with SEM. The centrifugation conditions involved in SEM sample preparation are 6000rpm, 5min, 4°C. Figure 2 (A) It can be seen that the CdS NPs synthesized in situ by microorganisms are distributed outside the cells in large quantities, and exist in two forms: riveted to the cell outer membrane and adhered to graphene. The microorganisms also adhere well to graphene. Figure 2 (B) Statistical analysis of particle size showed that the particle size of CdS NPs synthesized by biological method was about 28.10 nm. Figure 3 (AB) shows the scanning electron microscopy and corresponding energy spectrum results of the synthesized nanomaterials, which shows that the nanomaterials are composed of Cd and S elements, while the C and O elements reflect the microbial components well.

[0051] Raman spectroscopy (Raman) sample preparation: The living material obtained in (2) was purified, freeze-dried, ground into powder, resuspended in water, and then dropped onto a glass slide wrapped in tin foil. Under the conditions of 532 nm laser excitation, 50x objective, 10 mW laser power, 3 s exposure time, and 2 accumulations, the Raman spectrum of the mixed sample on the tin foil plate was obtained. The Raman shift range was 100 ~ 3000 cm -1Among them, the purification process is: first resuspend and wash with 2% sodium dodecyl sulfate (SDS, 55℃, water bath for 1 h) and proteinase K (100 ug / mL, 55℃, 0.5 h), and then ultrasonically disrupt (200 W, ultrasonic for 4 s, interval of 6 s, repeated 90 times) to lyse the bacteria and obtain the purified substance. Between different operations, the sample was washed with ultrapure water at least three times. I of graphene D / I G The value can reflect its redox state, Figure 4 (A) shows that graphene oxide was successfully reduced after microbial treatment. It is reported that RGO has a stronger conductivity than GO. The present invention relates to a relatively mild microbial method to successfully synthesize CdS NPs materials and RGO, and the nanomaterials, RGO and microorganisms are in close contact.

[0052] X-ray diffraction (XRD) sample preparation: The powdered solid sample in (3) was characterized. Figure 4 (B) is the XRD result, corresponding to the CdS card (PDF#10-0454), which once again proves the successful synthesis of CdS.

[0053] Test of transfer of photogenerated electrons between microorganisms and materials in living capacitor functional material S.oneidensis MR-1-CdS / RGO (PL spectrum): Steady-state photoluminescence (PL) spectrum is used to study the separation and transfer of carriers generated by light in a mixed system of biological materials or a material system. A series of living materials were synthesized according to the conditions optimized by (1) and (2), and a material control for bacterial inactivation was set up. The groups were divided into CdS / RGO / SW, CdS / SW, SW, CdS / RGO, and CdS. Figure 4 As shown in (C), the control bacteria SW has no intensity signal, while the photosensitizer CdS has the strongest intensity, indicating that the electrons and holes generated by CdS under photocatalysis are easy to recombine. Compared with CdS, the intensity of CdS / RGO and CdS / SW is reduced, and CdS / RGO / SW has the lowest intensity in the system containing materials, which shows that the introduction of RGO and SW is conducive to the separation of photogenerated electrons and holes. After the photoelectrons are generated by CdS, they are transferred to RGO and Shewanella SW, which makes it possible for the photoelectrons to enter the bacterial periplasmic space hydrogenase to produce hydrogen, and RGO is conducive to this process.

[0054] Example 2: Hydrogen production by light-dark cycle of living capacitor functional material S. oneidensis MR-1-CdS / RGO

[0055] (1) Construction of various living functional materials and control bacteria inactivation groups: According to the method of Example 1, different living capacitor functional materials were constructed, that is, with or without CdS or with or without RGO, and CdS / RGO / SW, CdS / SW, and RGO / SW groups were constructed. Pure Shewanella SW without materials was used as a control group; in addition, the living capacitor functional materials of different groups were ultrasonically crushed to inactivate (200 W, ultrasound for 4 s, interval of 6 s, repeated 90 times), and a control group for bacteria inactivation was obtained. The SW concentrations involved in the groups were all OD 600 = 0.2, the CdS concentration involved is 0.3 mM, and the RGO concentration involved is 50 mg / L.

[0056] (2) Light-dark cycle hydrogen production and capacitance performance experiment: The optimized living capacitance functional material S. oneidensis MR-1-CdS / RGO (0.3 mM CdS, 50 mg / L GO, OD 600 = 0.2) and the control set in Example 2 (1) are used for light-dark cycle hydrogen production and control pure darkness experiments. The composition of the liquid culture medium is shown in Tables 1 and 2. Figure 5 (A) and (C) show the hydrogen production results of each living functional material group under dark conditions, that is, the hydrogen production rate of CdS / SW is comparable to that of the control SW, about 0.12-0.17μmol / h / mg. The hydrogen production of CdS / RGO / SW is the highest, about 0.42μmol / h / mg, followed by RGO / SW, about 0.25μmol / h / mg, which indicates that RGO can improve the hydrogen production rate under dark conditions. Figure 5 As shown in (AC), under illumination, the hydrogen production rate of CdS / RGO / SW increased significantly to 6.48 μmol / h / mg, which was 15.4 times that under dark conditions, while there was no significant increase in the other groups. When the light source was removed, the hydrogen production rate of the CdS / RGO / SW group was still very high, about 3.04 μmol / h / mg, which was 0.47 times that under illumination, and there was no significant change in the other groups. The results show that the living capacitor functional material S. oneidensis MR-1-CdS / RGO has a good activation effect under light conditions, which promotes its continuous hydrogen production under dark conditions. In addition, in order to locate the hydrogen production site, different bio-material coupling bodies were treated with ultrasonic disruption to lyse cells, which are metabolically inactive but retain the photoactivity of CdS semiconductors, known as cleaved hybrids, as described in Example 2 (1), including CdS / RGO, CdS and RGO, and then a similar hydrogen production process as described above was carried out. Figure 5 (AB) and Figure 5The results of (D) show that the hydrogen production of the lysate group is negligible under dark and light-dark cycle conditions compared with the living material group. In summary, the living capacitive functional material S. oneidensis MR-1-CdS / RGO is a capacitor for light-activated and dark-sustained hydrogen production. In addition, the production of hydrogen is mediated by microorganisms rather than spontaneous abiotic reactions. Therefore, light-promoted and dark-sustained hydrogen production was achieved by coupling the biogenic CdS / RGO material with S. oneidensis MR-1.

[0057] Example 3: Study on the capacitance mechanism of the living capacitor functional material S. oneidensis MR-1-CdS / RGO

[0058] (1) Intracellular NADH / NAD in bacteria + Changes of redox pairs under light-dark cycles: Figure 6 (A) shows the NADH and NAD under light-dark cycle + Relative content changes, when the light source is irradiated, NADH / NAD + The value gradually increases, and after removing the light source, NADH / NAD + The value gradually decreases. This indicates that when NAD + After the light source is removed, NADH is reduced again, that is, when exposed to light, the microorganisms give the excess photoelectrons to NAD. + It is converted into NADH to store electrons, and releases electrons in the dark. Therefore, the capacitance performance of the system is partly derived from the intracellular NADH / NAD + Buffering capacity of redox couple.

[0059] (2) Capacitive properties of materials: It has been reported that chemically synthesized GO and GO / metal composites have capacitive properties and can be used in capacitor design. This raises the question of whether biosynthesized RGO or CdS / RGO has capacitive properties. Figure 6 As shown in (BD), the cyclic voltammetry curves of GO and biogenic CdS / RGO, CdS and RGO at a scan rate of 100 mV / s were measured. GO and the background showed negligible current response, but the CV curves of biogenic RGO and CdS / RGO showed very high currents. Both had rectangular features, which are typical features of electric double layer (EDL) capacitors. The specific capacitances of biogenic RGO and CdS / RGO were 276.18 and 149.28 F, respectively. -1 , which is significantly higher than that of biogenic CdS (13.29 F -1 ) and GO (15.22F -1 ).also, Figure 6(E) The CV curve shape of biogenic CdS / RGO does not change significantly at different scanning speeds, indicating that biogenic CdS / RGO has stable capacitance. Figure 6 (F) shows the constant current charge-discharge (GCD) curves of bio-derived CdS / RGO at different current densities, which are symmetrical triangle curves, indicating that the bio-derived CdS / RGO capacitor has good reversibility and meets the EDL characteristics. In order to quantitatively evaluate the electron transfer capacity (ETC) of bio-derived CdS / RGO, CdS, RGO and chemical GO, two electrochemical parameters, namely, electron acceptance (EAC) and electron donation (EDC) capacity, were studied. Figure 6 (G), the EACs of biogenic CdS / RGO, CdS, RGO, and chemically synthesized GO are 0.43, 0.18, 0.86, and 0.29 mmol e, respectively. - / g, and EDC were 0.62, 0.13, 0.53 and 0.04 mmol e, respectively. - / g. The specific test process is: in a standard three-electrode system, mesh glassy carbon (RVC) is used as the working electrode, platinum wire electrode (Pt) is used as the counter electrode, Ag / AgCl electrode is used as the reference electrode, 0.1mM phosphate buffer (PB, pH = 7.0) is used as the electrolyte, and anthraquinone-2,6-disulfonic acid disodium (AQDS) and diquat (DQ) are used as mediators for electrochemical media. The electron acceptance / donation capacity (EAC / EDC) is obtained by mediated electrochemical oxidation (MEO) and mediated electrochemical reduction (MER). These results show that biogenic CdS / RGO has good capacitance and can achieve the purpose of storing and releasing electrons in the living capacitor functional material S. oneidensis MR-1-CdS / RGO.

[0060] (3) Capacitive properties of extracellular polymers (EPS): Figure 6 (H) is the UV-visible (UV-vis) spectrum of EPS. The peaks of riboflavin and c-type cytochrome with reversible redox properties are at 267 nm and 410 nm, respectively. The results show that the expression of riboflavin and c-type cytochrome in the EPS secreted by Shewanella in the living capacitor functional material S. oneidensis MR-1-CdS / RGO system is promoted. In order to quantitatively evaluate the electron exchange capacity of EPS released by Shewanella in the CdS / RGO / SW mixed system, the same operation as in Example 3 (2) was performed, as shown in FIG. Figure 6 As shown in (I), the EAC and EDC corresponding to EPS were 1.16 and 1.13 mmol e - / g. These results indicate that the EPS released by Shewanella in the CdS / RGO / SW mixed system also has the function of storing and releasing electrons.

[0061] In summary, the good capacitance performance of the living capacitor functional material CdS / RGO / SW is due to the EDL characteristics of the biogenic CdS / RGO, the reversible redox properties of EPS released by Shewanella, and the NAD + The result of the combined action of the conversion of / NADH redox pair.

[0062] Comparative Example 1: Comparison of bacterial activity and hydrogen production performance of the living capacitor functional material S. oneidensis MR-1-CdS / RGO under light-dark cycle and continuous illumination

[0063] (1) Bacterial activity of the living capacitor functional material S.oneidensis MR-1-CdS / RGO under light-dark cycle and continuous illumination: The living capacitor functional material S.oneidensis MR-1-CdS / RGO optimized and constructed in Example 1 was subjected to light-dark cycle (light-dark cycle alternating 12 h -12 h, 4 cycles, 96 h in total) and continuous illumination (96 h in total) experiments. After the catalytic reaction was completed, each group was transferred to culture at a ratio of 1:100, and the culture conditions were 200 rpm, 30°C, 12 h, and the OD was measured. 600 The absorbance value is used to determine the bacterial activity. Figure 7 (A) It is known that the activity of bacteria under light-dark cycle conditions is higher than that under continuous illumination, which indicates that a certain degree of dark alternation can help bacteria alleviate the toxic effects of photocatalysis.

[0064] (2) Comparison of hydrogen production performance of living capacitor functional material S. oneidensis MR-1-CdS / RGO under light-dark cycle and continuous illumination: Figure 7 (B) shows the hydrogen production per unit liquid volume of the light-dark alternation and continuous illumination groups in Comparative Example 1 (1) after 96 hours of reaction. The results show that the total hydrogen production of the light-dark alternation after long-term operation is higher than that of the continuous illumination, which is 296.56 and 203.89 mmol / L respectively. Combined with the bacterial activity results after the transfer culture of Comparative Example 1 (1), it further shows that the light-dark alternation helps to alleviate the toxic effects of continuous illumination on bacteria, thereby making the light-dark alternation group more sustainable in hydrogen production and ultimately higher in total hydrogen production.

[0065] Comparative Example 2: Comparison of the properties and performance of chemically synthesized CdS / RGO and biologically synthesized CdS / RGO

[0066] (1) Method for chemical synthesis of CdS / RGO: 0.514 g CdCl2·2.5H2O, 0.19 g thiourea, and 1 g polyvinyl pyrrolidone (PVP) were mixed in 50 mL ethylene glycol under stirring conditions, and then 2.5 mL GO mixed solution (150 mg GO / 15 mL ethylene glycol mixed solution) was added. After stirring, the mixture was subjected to hydrothermal reaction at 160°C for 12 h. Subsequently, the synthesized CdS / RGO (which has the same content and ratio as the precursor of biologically synthesized CdS / RGO, i.e., 0.3 mM CdS and 50 mg / L GO) was obtained by washing the mixture several times.

[0067] (2) Performance index test of the CdS / RGO material synthesized by chemical method in this example: Figure 8 The morphology characteristics of chemically synthesized CdS / RGO materials, its CdS particle size distribution and XRD results are shown. The results show that CdS in chemically synthesized materials is also in close contact with RGO, but its particle size is about 1037.9nm, which is much larger than the 28.14 nm of the biological method. Figure 8 (C) shows that the XRD of the chemically synthesized material corresponds to the CdS card (PDF#41-1049), which belongs to the hexagonal system; Figure 4 (B) XRD of biologically synthesized materials corresponds to CdS card (PDF#10-0454), which belongs to the cubic system. Cubic CdS is generally considered to have better photocatalytic performance due to its higher carrier migration rate and charge separation efficiency, as well as its excellent performance when forming heterojunctions. The above results show that biologically synthesized and chemically synthesized CdS / RGO are completely different materials, especially the photosensitizer CdS, which is reflected in many aspects such as morphology, particle size and crystal form.

[0068] (3) Construction of living capacitor functional material S. oneidensis MR-1-CdS / RGO from different sources of CdS / RGO (biosynthesized and chemically synthesized): For the in situ biological construction of living capacitor functional materials, the method was the same as in Example 1. A chemical comparison was set up, specifically, the chemically synthesized CdS / RGO in Comparative Example 2 (1) was mixed with Shewanella cultured to the late logarithmic stage according to the same concentration ratio as in Example 1 (OD600 = 0.2, CdS = 0.3 mM, RGO = 50 mg / L).

[0069] (4) Comparison of photocatalytic hydrogen production of living capacitor functional material S. oneidensis MR-1-CdS / RGO (CdS / RGO synthesized by biological method and chemical method): Fig. 9(AB) shows the hydrogen production of the capacitor functional material S.oneidensis MR-1-CdS / RGO constructed by the biological in-situ method and the chemical dosing method in pure darkness or light-dark cycle. The reaction conditions and operations are the same as in Example 2. The results show that the two have equivalent capabilities in the dark, about 0.41-0.49 μmol / h / mg. Under illumination, the hydrogen production rate of the biological in-situ construction group is 6.28 μmol / h / mg, which is higher than the 2.87 μmol / h / mg of the chemical dosing group, which are 14.9 and 7.0 times in the dark, respectively, indicating that the photocatalytic system constructed in situ by the biological method has better hydrogen production effect. When the light source is removed, the hydrogen production rate of the biological in-situ construction group is still very high, about 2.57 μmol / h / mg, which is 0.41 times that under illumination, while the chemical dosing group is 0.98 μmol / h / mg, which is 0.34 times that under illumination, which is lower than the biological method. The results show that the photocatalytic and capacitive properties of the living capacitor functional material S. oneidensis MR-1-CdS / RGO constructed by the biological in situ method are better than those by the chemical addition method. This is due to the better performance of the photosensitizer CdS in the biologically synthesized material and the better bio-material interface when the coupling system is constructed in situ.

[0070] In summary, compared with continuous illumination conditions, the living capacitor functional material S. oneidensis MR-1-CdS / RGO in this study has higher biological activity, stronger average hydrogen production rate and sustainability under light-dark alternation conditions, which better conforms to the daily changes of sunlight during the day and night, and has the potential for practical application. Compared with the chemical synthesis addition method, the living capacitor functional material S. oneidensis MR-1-CdS / RGO constructed based on biological in situ in the present invention has stronger performance in photocatalysis and capacitor hydrogen production.

[0071] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An application of a living carbonaceous semiconductor material in hydrogen production, characterized in that: The living capacitor functional material S.oneidensis MR-1-CdS / RGO was transferred into a liquid inorganic salt culture medium that was fully aerated with nitrogen, and catalytically produced hydrogen under light or light-dark cycle conditions; The living capacitor functional material S. oneidensis MR-1-CdS / RGO is prepared by a method comprising the following steps: Step 1: Cultivate the dissimilatory metal-reducing bacteria in LB medium until the early stage of the plateau; Step 2: The dissimilatory metal-reducing bacteria cultured to the early stage of the platform in step 1 are resuspended in a culture medium containing thiosulfate for anaerobically cultured, and then Cd(II)-EDTA and graphene oxide GO are added to the culture system. Anaerobically culture is performed until Cd(II) is completely converted into CdS NPs semiconductors, thereby constructing a living capacitor functional material S. oneidensis MR-1-CdS / RGO.

2. The use according to claim 1, characterized in that: In step 1, the dissimilatory metal-reducing bacteria stored at -80°C were streaked on a plate, cultured aerobically for 48 h, and then single colonies were selected and placed in LB liquid culture medium. After another 12 h of aerobic culture, they were transferred to fresh LB liquid culture medium at a ratio of 1:10 and continued to be cultured aerobically for 12 h.

3. The use according to claim 2, characterized in that: The dissimilatory metal-reducing bacteria is the wild-type WT strain of S. oneidensis MR-1.

4. The use according to claim 1, characterized in that: In step 2, the culture medium containing thiosulfate is based on LB liquid culture medium, to which thiosulfate is added, and the concentration of thiosulfate is between 0.1-5 mM.

5. The use according to claim 1, characterized in that: In step 2, the concentration of Cd(II)-EDTA in the culture system is between 0.1-5 mM.

6. The use according to claim 1, characterized in that: In step 2, the concentration of graphene oxide GO in the culture system is between 10-500 mg / L.

7. The use according to claim 1, characterized in that: In step 2, the anaerobic culture time with thiosulfate is 6-12 h.

8. The use according to claim 1, characterized in that: In step 2, the culture time after adding Cd(II)-EDTA and graphene oxide GO is 6-12 h.

9. The use according to claim 1, characterized in that: When catalyzing hydrogen production under light-dark cycle conditions, the light-dark time ratio is 1:1.

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