Nitrogen-doped Graphene Hydrogels Research Articles

Construction of high–loading 3D Co[sbnd]N[sbnd]C catalyst for oxygen reduction reaction in Zn–air batteries

The development of single atom catalysts is considered as a hotspot in the field of electrocatalysis. As the representative of single atom catalysts, metal and nitrogen co–doped carbon (MNC) attracts worldwide attentions due to its great potential in the application of oxygen reduction reaction (ORR). However, the actual preparation of MNC still confronts with tedious procedure, harsh condition and relatively low loading of single metal atom. In this work, we successfully prepare high–loading 3D CoNC architecture by a facile oxidation polymerization followed by pyrolysis process employing 3D nitrogen–doped graphene hydrogel (NGH) and pyrrole (PY) as the reaction precursors. Benefitting from the individual advantages of 3D NGH and PY, the resultant 3D CoNC possesses unique 3D architecture, high–loading single Co atom (2.74 wt%), large specific surface area and enriched mesopores, which benefit the exposure of sufficient catalytic sites and facilitate electrons transfer and ions transport, thus generating much enhanced ORR performance. When used as the cathode catalyst for zinc–air batteries (ZABs), it shows comparable performance with commercial Pt/C catalyst. Clearly, our finding offers a good guidance on the design and synthesis of advanced high–loading single atom catalysts.

Prussian blue analogue-derived hollow metal oxide heterostructure for high-performance supercapacitors.

Supercapacitors (SCs) have been the subject of considerable interest because of their distinct advantages. The performance of SCs is directly affected by the electrode materials. Metal oxides derived from Prussian blue analogues (PBAs) are often used as electrode materials for SCs. Herein, we developed a multi-step strategy to fabricate ternary hollow metal oxide (CuO/NiO/Co3O4) heterostructures. The core-shell structured PBA (NiHCC@CuHCC) with Ni-based PBA (NiHCC) as the core and Cu-based PBA (CuHCC) as the shell was prepared by a crystal seed method. The ternary metal oxide (CuO/NiO/Co3O4) with a hollow structure was obtained by calcinating NiHCC@CuHCC. The prepared CuO/NiO/Co3O4 demonstrates an excellent specific capacitance of 262.5 F g-1 at 1 A g-1, which is 27.4% and 16.2% higher than those of CuO/Co3O4 and NiO/Co3O4, respectively. In addition, the material showed outstanding cycling stability with a capacitance retention of 107.9% after 3000 cycles. The two-electrode system constructed with CuO/NiO/Co3O4 and nitrogen-doped graphene hydrogel (NDGH) demonstrates a stable and high energy density of 27.1 W h kg-1 at a power density of 1037.5 W kg-1. The capacitance retention rate was 100.7% after 4000 cycles. The reason for the excellent electrochemical properties could be the synergistic effect of the introduced heterojunction of CuO/NiO, the hollow structure, and various metal oxides. This strategy can greatly inspire the construction of SC electrodes.

Influence of aqueous electrolytes on the electrochemical behavior of nitrogen-doped graphene hydrogel electrodes for supercapacitors

The charge storage behaviors of a nitrogen-doped graphene hydrogel are systematically analyzed before and after cycling in different aqueous electrolytes.

Synthesis of NiCo-LDH@nitrogen-doped graphene hydrogel/nickel foam composites with 3D hierarchical structure for supercapacitors

Nickel-cobalt layered double hydroxide (NiCo-LDH)@N-GH/NF composites were prepared by a simple one-pot hydrothermal method on nickel foam (NF) substrates loaded with 3D porous nitrogen-doped graphene hydrogel (N-GH). 3D hierarchical structure has a positive role in promoting electrochemical performance. When used as supercapacitor electrodes, NiCo-LDH@N-GH/NF shows a specific capacity of 174.1 mAh·g−1 (specific capacitance of 1393F·g−1) at 1 mA·cm−2. The assembled NiCo-LDH@N-GH/NF//GH/CNT asymmetric supercapacitor (ASC) has a specific capacitance of 209F·g−1 (1 mA·cm−2). When the power density is 260 W·kg−1, the energy density reaches 63.33 Wh·kg−1.

Non-noble metal plasmonic enhanced photoelectrochemical sensing of chlorpyrifos based on 1D TiO2-x/3D nitrogen-doped graphene hydrogel heterostructure.

Low-cost and resource-rich non-noble metal plasmonic materials have attracted tremendous attention as potential substitutes for plasmonic noble metals. Herein, 3D nitrogen-doped graphene hydrogels (NGH) decorated with Ti3+ self-doped 1D rod-shaped titanium dioxide nanorods (TiO2-x NR), 10-25nm in size, were prepared by a facile one-step method. It was found that the as-fabricated TiO2-x NR/NGH showed a synergistic effect, displaying enhanced photoelectrochemical (PEC) activity by controlling the nanoscale architecture and improving the electronic properties, while also producing abundant oxygen vacancies, which extended the light harvesting and suppressed the recombination of electron-hole pairs induced by the non-noble metal surface plasmon resonance (SPR) effect. In particular, the transient-state photocurrent intensity of the TiO2-x NR/NGH composites was 5.1 times as high as that of pure TiO2. Therefore, the TiO2-x NR/NGH composites could serve as a substrate material for PEC sensing, providing a good basis for selective and sensitive detection of chlorpyrifos. Under optimal conditions, the constructed PEC sensor was found to have several advantages including a broad linear range (0.05ng/mL-0.5μg/mL), low detection limit (0.017ng/mL), and considerable stability, demonstrating that the sensor may offer a promising route in the field of environmental analysis.

Nitrogen-doped nanoporous graphene induced by a multiple confinement strategy for membrane separation of rare earth.

SummaryRare earth separation is still a major challenge in membrane science. Nitrogen-doped nanoporous graphene (NDNG) is a promising material for membrane separation, but it has not yet been tested for rare earth separation, and it is limited by multi-complex synthesis. Herein, we developed a one-step, facile, and scalable approach to synthesize NDNG with tunable pore size and controlled nitrogen content using confinement combustion. Nanoporous hydrotalcite from Zn(NO3)2 is formed between layers of graphene oxide (GO) absorbed with phenylalanine via confinement growth, thus preparing the sandwich hydrotalcite/phenylalanine/GO composites. Subsequently, area-confinement combustion of hydrotalcite nanopores is used to etch graphene nanopores, and the hydrotalcite interlayer as a closed flat nanoreactor induces two-dimensional space confinement doping of planar nitrogen into graphene. The membrane prepared by NDNG achieves separation of Sc3+ from the other rare earth ions with excellent selectivity (∼3.7) through selective electrostatic interactions of pyrrolic-N, and separation selectivity of ∼1.7 for Tm3+/Sm3+.

Multi-dimensional Pt/Ni(OH)2/nitrogen-doped graphene nanocomposites with low platinum content for methanol oxidation reaction with highly catalytic performance

Direct methanol fuel cell has been widely recognized as the ideal renewable energy conversion device. However, it still suffers from two major limitations: the heavy use of precious metal platinum and the sluggish kinetics of methanol oxidation catalytic reaction, which have prevented its large-scale commercialization. Therefore, it is considered desirable to design rational and greatly effective catalysts. In this work, multi-dimensional ternary composite electrocatalysts of Pt/Ni(OH)2/nitrogen-doped graphene catalysts have been synthesized with 0D Pt nanoparticles on the 2D Ni(OH)2 nanosheets supported by 3D porous nitrogen-doped graphene hydrogel, and with a low amount (4.26 wt%) of Pt. Notably, the multi-dimensional porous structure design, abundant hydroxyl species, and mutual interactions of ternary catalysts endow high activity promoting the poisonous CO or CO-like intermediates oxidation and propelling the kinetics of sluggish MOR. These novel Pt/Ni(OH)2/NG catalysts exhibit an excellent mass activity of 2.99 A mg−1Pt for methanol electrooxidation, which is about 2.8 and 4.8 times higher than those of commercial PtRu/C and Pt/C, respectively. Furthermore, both durability and CO tolerance of Pt/Ni(OH)2/NGs electrocatalysts are significantly improved.

A novel edge-rich structure of CuO/Co3O4 derived from Prussian blue analogue as a high-rate and ultra-stable electrode for efficient capacitive storage

Metal oxides derived from Prussian blue (PB) and Prussian blue analogues (PBAs) are usually used as electrode materials of supercapacitors (SCs). However, the disadvantage is few external active sites. We have successfully developed a novel yet facile strategy to prepare a novel Cu-Co mixed metal oxide (CuO/Co3O4) derived from Cu-based PBA (Cu3[Co(CN)6]2•9H2O), which can form the edge-rich structure to expose more active sites. The edge-rich structure greatly improves charge storage kinetics of electrode material, and the capacitive contribution can even reach 99% at a scan rate of 10 mV s − 1. Even at a low specific surface area, this novel electrode material possesses excellently ultra-stable and high-rate performance in 2 M KOH aqueous electrolyte (76.7% capacity retention when the current density increases from 1 to 10 A g − 1). Moreover, the hybrid supercapacitor (HSC) fabricated with the positive electrode edge-rich CuO/Co3O4 and the negative electrode nitrogen-doped graphene hydrogel (NDGH) delivers remarkable cycling stability (After 7000 cycles, 98.9% capacity is maintained). These excellent electrochemical performances can be attributed to a novel edge-rich structure, which is beneficial for exposing active sites in the external surface and thus promotes the capacitive contribution for fast redox reaction. This strategy opens up a new avenue for promoting electrochemical performance by mediating interfaces and can be extended to the fields of battery and electrocatalysis.

In Situ Formation of "Dimethyl Sulfoxide/Water-in-Salt"-Based Chitosan Hydrogel Electrolyte for Advanced All-Solid-State Supercapacitors.

Biodegradable hydrogel electrolytes are particularly attractive in the fabrication of all-solid-state supercapacitors due to environmental benignity and avoiding of leakage. The introduction of "water-in-salt" (WIS) electrolytes into hydrogels will further broaden the electrochemical stability window of aqueous supercapacitors significantly. Meanwhile, the addition of an organic co-solvent can effectively overcome the inevitable salt precipitation and extend the temperature adaptability. Herein, an in situ cross-linking approach was demonstrated without any extra binder to obtain a "dimethyl sulfoxide/water-in-salt"-based (DWIS) chitosan hydrogel electrolyte. Interestingly, the addition of 4-7 mol L-1 of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts not only conforms to the criterion of WIS, but also promoted the successful gelation through the supramolecular complexation between Li+ -solvated complexes and chitosan chains. A hydrogel-based all-solid-state supercapacitor was fabricated using the DWIS chitosan hydrogel as the electrolyte and separator while nitrogen-doped graphene hydrogel (NG) was used as the electrode. The optimized supercapacitor with a wide operating voltage of 2.1 V showed a high specific capacitance of 107.6 F g-1 at 1 A g-1 , remarkable capacitance retention of 80.1 % after 5000 cycles, a superior energy density of 62.9 Wh kg-1 at a power density of 1025.5 W kg-1 , and excellent temperature stability in the range of -20 to 70 °C. These findings suggest that the as-prepared hydrogel electrolyte holds great potential in the practical application of high-performance solid-state energy storage devices.

Prussian blue analogue derived low-crystalline Mn2O3/Co3O4 as high-performance supercapacitor electrode

Metal oxide-based supercapacitors have been widely studied due to their high theoretical specific capacitance. Among many preparation methods of metal oxides, the annealing treatment of metal-organic frameworks (MOFs) has unique advantages in designable and well-controlled structure, and this approach is regarded to be suitable for preparing the metal oxides with high crystallinity. At present, it is still a great challenge to obtain low-crystalline MOFs-derived metal oxides. In this study, we have skillfully taken advantage of polyvinyl pyrrolidone (PVP) in Mn-based Prussian blue analogue (PBA) and formed the low-crystalline Mn2O3/Co3O4 composite by an annealing process. The presence of PVP can weaken the crystallization of metal oxides during the annealing process and create structural disorder. The as-prepared low-crystalline Mn2O3/Co3O4 has an excellent specific capacitance of 478.7 F g−1 at a current density of 1 A g−1, which is 131.7% higher than the high-crystalline counterpart. Moreover, this material exhibits outstanding cycling stability (116.4% capacitance retention after 2500 cycles). The asymmetric supercapacitor consisting of low-crystalline Mn2O3/Co3O4 as the positive electrode and nitrogen-doped graphene hydrogel as the negative electrode delivers an energy density of 32.8 Wh kg−1 at a power density of 1190.1 W kg−1. The superior electrochemical performances are mainly ascribed to the formation of low-crystalline Mn2O3/Co3O4 that provides more reversible active sites and accelerates ion diffusion. It is expected to open up a new avenue to the preparation of low-crystalline metal oxides for electrochemical energy storage.

Boosting the cyclic stability and supercapacitive performance of graphene hydrogels via excessive nitrogen doping: Experimental and DFT insights

Nitrogen-doped mesoporous graphene hydrogel (MGHG) enjoys many unique characteristics for use as an efficient energy storage electrode material. Herein, a green one-pot hydrothermal synthesis strategy was employed to synthesize highly hydrophilic nitrogen-doped mesoporous graphene hydrogel. The morphological, structural, and compositional analyses were performed using FESEM, XRD, and XPS techniques. The as-prepared MGHG exhibits high wettability (contact angle = 58.9o), high surface area (318.226 m2/g), and an unprecedented nitrogen doping content of 2.95%. The fabricated MGHG was evaluated as a supercapacitor material in 1 M aqueous K2SO4 electrolyte, revealing a maximum specific capacitance of 595.7 F.g−1 with a low equivalent series resistance (0.1664 Ω) that is ascribed to the high porosity, high surface area, and the available nitrogen redox active sites. To further elucidate the electrochemical performance of MGHG, a symmetric supercapacitor device was assembled using MGHM as negative and positive electrodes. The fabricated device shows a maximum specific energy of 30 Wh kg−1 corresponding to a specific power 1000 W kg−1. The density functional theory (DFT) computations were utilized to better understand the high performance of the assembled devices. These superior results demonstrate the excellent performance of MGHG as a potential material for highly-performing supercapacitor devices with a potential window of 2.2 V.

Using carbamide for preparing nitrogen-doped graphene hydrogels to enhance supercapacitor performance

ABSTRACTIn this paper, nitrogen-doped graphene hydrogel (NGH) has been synthesised by chemically reducing aqueous graphene oxide (GO) solution in the presence of carbamide.Its nitrogen content reaches 8.97 at%. It exhibits a 3D porous network structure with pore sizes of about 2 to 4 μm comparable to the graphene hydrogel (GH) prepared without nitrogen source. Meanwhile, the NGH shows same hierarchical mesoporous structure with dominant pore size about 2–5 nm as the GH’s. Besides, its specific surface area (132.8 m2 g−1) is higher than that of the GH (122.9 m2 g−1). The NGH can deliver an enhanced specific capacitance of 199.80 F g−1 at 2 A g−1 compared to that of the GH (142.23 F g−1). In addition, the NGH can retain 62.6% of specific capacitance from 2 to 50 A g−1. The NGH also can maintain 97% of its initial specific capacitance after 20,000 cycles at 10 A g−1.

Three-dimensionally assembled manganese oxide ultrathin nanowires: Prospective electrode material for asymmetric supercapacitors

In this report, we have forwarded a noble synthesis route for the fabrication of self-supported three-dimensional networks of manganese oxide ultrathin nanowires (3D MnO2-UTNWs) via a simple and cost-effective process for the first time. The formation of ultrathin nanowires (5 nm in diameter with several micrometer lengths) and their 3D assembly was achieved via a slow-reduction of potassium permanganate by oleylamine under constant stirring at 80 °C for 50 h. The resultant material was characterized using FE-SEM, TEM, XRD, FTIR, BET, XPS and Raman techniques. As-fabricated 3D MnO2-UTNWs network was used as the electrode material for supercapacitor. The electrochemical studies of the material revealed an excellent electrochemical performance with a high specific capacitance of 544.7 Fg-1 at 1 Ag-1 and excellent life span of 86.3% after 5000 cycles. An asymmetric supercapacitor was assembled using 3D-MnO2 UTNWs and nitrogen-doped graphene hydrogels (NGHs) as the positive and negative electrodes; respectively. The 3D-MnO2 UTNWs//NGHs device delivered an admirable specific capacitance of 56.5 Fg-1 at 1 Ag-1, energy density of 21 Whkg−1 at 840 Wkg-1, and extraordinary cyclic stability of 81.3% after 5000 cycles. This method provides a novel green synthetic route to prepare 3D MnO2-UTNWs without utilizing non-ambient reaction parameters.

Three-Dimensional-Structured Boron- and Nitrogen-Doped Graphene Hydrogel Enabling High-Sensitivity NO2 Detection at Room Temperature.

Heteroatom-doping has been proved as an effective method to modulate the electronic, physical, and chemical properties of graphene (Gr). Developing a new strategy of heteroatom-doping for high-performance gas sensing is a pivotal issue. Here, we demonstrate novel Gr-based gas sensors through three-dimensional (3D)-structured B-/N-doping nanomaterials for high-performance NO2 sensing. The 3D porous B- and N-doped reduced graphene oxide hydrogels (RGOH) are synthesized via one-step hydrothermal self-assembly and employed as transducing materials to fabricate room-temperature high-performance chemiresistors. The systematic characterizations of the as-synthesized B- and N-RGOH clearly show the uniform doping of the B and N heteroatoms and the formation of B and N components with C/O. In comparison with the pristine RGOH counterpart, the 3D B- and N-RGOH sensors exhibit 38.9 and 18.0 times enhanced responses toward 800 ppb NO2, respectively, suggesting the remarkable doping effect of the heteroatoms in improving the sensitivity. Significantly, B- and N-RGOH display the exceptionally low limit of detection of 9 and 14 ppb NO2, respectively, which are much lower than the threshold limit recommended by the U.S. Environmental Protection Agency. In addition, the developed NO2 sensors show good linearity, reversibility, fast recovery, and impressive selectivity. This work opens up a new avenue to fabricate room-temperature and high-performance NO2 sensors by incorporating B and N heteroatoms into 3D RGOH via a convenient hydrothermal self-assembly approach.

Oleylamine-assisted synthesis of manganese oxide nanostructures for high-performance asymmetric supercapacitos

This work reports a simple and cost-effective synthesis path to fabricate manganese dioxide nanostructures with controlled morphologies. Herein, we have used oleylamine as a reducing, surfactant, and structure directing agent. The treatment of MnO2 precursor with the varying concentration of oleylamine led to the formation of different morphologies of MnO2 (nanorods, nanoflowers and three-dimensional MnO2 spheres). The as-synthesized nanostructures were characterized by various techniques and their electrochemical performances were studied. When used as an electrode material for supercapacitors, 3D-MnO2 exhibited a higher specific capacitance of 450 Fg−1 and admirable cyclic stability (~91.7%) after 5000cycles, which were higher than that of the other formulations. Moreover, an asymmetric supercapacitor was assembled by using as-prepared 3D-MnO2 and nitrogen-doped graphene hydrogels as the positive and negative electrodes, respectively. As-fabricated asymmetric device delivered specific capacitance of 49.44 Fg−1 at 1 Ag−1 an outstanding energy density of 20 Whkg−1 at 857.14 Wkg−1, and retained ~93.15% stability after 5000cycles. The obtained results showed that the as-synthesized 3D-MnO2 can be considered as the positive electrode material in supercapacitors.

Engineering nanohaired 3D cobalt hydroxide wheels in electrospun carbon nanofibers for high-performance supercapacitors

Engineering nanostructures in the desired design and suitable size is one of the key issues for persuading high-performance supercapacitors (SCs). In this work, we report a successful synthesis of a new type of nanohaired three-dimensional cobalt hydroxide wheels/carbon nanofibers (3D Co(OH)2/CNFs) composite by a cost-effective electrospinning cum hydrothermal method. The 3D Co(OH)2 wheels are composed of many partially-fused, nanohaired and serrated sheet-like nanoleaflets furnishing abundant active sites. This novel architecture is quite significant for the stability of the composite since the wheels encircle one or more conductive CNFs firmly rather than the simple attachment on the surface of substrate. The growth process of 3D Co(OH)2 wheels on CNFs has been studied by synthesizing other two novel Co(OH)2/CNFs composites. The as-prepared material exhibits a specific capacitance of 1186 F g−1 at a current density of 1 A g−1 with excellent cyclic stability which is the highest reported value for Co(OH)2/CNFs composites. The asymmetric supercapacitor (ASC) device assembled using 3D Co(OH)2/CNFs as a positive electrode and nitrogen doped graphene hydrogel (NGH) as a negative electrode exhibits a high energy density of 60.31 W h kg−1 at power density of 740.8 W kg−1 which still remains 37 W h kg−1 even at a higher power density of 7500 W kg−1 with remarkable cycle life. Therefore, the composite stands as a promising candidate for SCs electrode material. This unique nanoengineering gives an insight into the synthesis of other stable nanocomposites for diverse applications like sensors, catalysis, etc.

Three-dimensional nitrogen-doped graphene hydrogel supported Co-CeOx nanoclusters as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

The development of highly active noble-metal-free catalysts for catalytic hydrolysis of ammonia borane is mandatory for its application in hydrogen storage. Herein, Co-CeOx nanoclusters have been successfully anchored on a three-dimensional nitrogen-doped graphene hydrogel (NGH) by a simple co-reduction method and further used as efficient catalysts to catalytic hydrolysis of ammonia borane at room temperature. Thanks to the strong synergistic electronic effect between Co and CeOx, as well as the strong metal-support interaction between Co-CeOx and 3D NGH, the as-synthesized Co-(CeOx)0.91/NGH catalyst exhibits superior catalytic activity toward hydrolysis of ammonia borane, with the turnover frequency (TOF) value of 79.5min−1, which is almost 13 times higher than that of Co/NGH, and higher than most of the reported noble-metal-free catalysts.

Facile one-pot synthesis of visible light-responsive BiPO4/nitrogen doped graphene hydrogel for fabricating label-free photoelectrochemical tetracycline aptasensor

It is fundamental to develop highly efficient visible light-responsive photoelectrochemical (PEC) performance material for fabricating PEC biosensor. Herein, BiPO4/three-dimensional nitrogen doped graphene hydrogel (3DNGH) nanocomposites were prepared for the first time via a facile one-pot hydrothermal route. In this nanoarchitecture, the BiPO4 nanorods were anchored onto the porous structure of 3DNGH. Compared with pristine BiPO4, the absorption of BiPO4/3DNGH has been extend to visible-light region, and the energy band gap of BiPO4/3DNGH was calculated to be 2.10 eV, which was greatly narrower than that of pristine BiPO4 with a band gap of 3.85 eV. Under visible light irradiation, the photocurrent signal of the as-prepared BiPO4/3DNGH was 847.2-fold, 4.1-fold and 2.3-fold enhanced comparing to pristine BiPO4, BiPO4 functionalized reduced graphene oxide and BiPO4/nitrogen doped graphene. The enhancement of such photocurrent signal was attributed to the introduction of 3DNGH, which was capable to improve the charge transfer rate and also the efficiency of visible-light utilization of BiPO4. Based on the excellent PEC properties of BiPO4/3DNGH, a label-free PEC aptasensor for selectivity and sensitivity detection of tetracycline (Tc) was successfully established by using Tc aptamer as a biorecognition element. Under optimized conditions, the proposed PEC aptasensor exhibited a wide linear in the range from 0.1 nmol L−1 to 1 μmol L−1 as well as a low detection limit of 0.033 nmol L−1 (S/N = 3). The prepared BiPO4/3DNGH nanocomposites would serve as a promising visible light-responsive photoactive material for fabrication of PEC biosensors with high performance.

CoBP nanoparticles supported on three-dimensional nitrogen-doped graphene hydrogel and their superior catalysis for hydrogen generation from hydrolysis of ammonia borane

P-doped noble-metal-free CoB nanoparticles (NPs) anchored on a three-dimensional nitrogen-doped graphene hydrogel (NGH) have been successfully synthesized trough a simple one-pot co-reduction method and further used as catalyst toward catalytic hydrolysis of ammonia borane (NH3BH3) at room temperature. Benefiting from the synergistic electronic effect between Co, B, and P, as well as the strong metal-support interaction between CoBP and 3D NGH, the as-synthesized Co0.79B0.15P0.06/NGH catalyst exhibits excellent catalytic activity toward hydrolysis of ammonia borane, with the turnover (TOF) value of 32.8 min−1, which is almost 5 times higher than that of undoped Co0.85B0.15/NGH NPs, and higher than most of the reported noble metal free catalysts.

Multiple signal-amplification via Ag and TiO2 decorated 3D nitrogen doped graphene hydrogel for fabricating sensitive label-free photoelectrochemical thrombin aptasensor

In this study, Ag/TiO2/3D nitrogen doped graphene hydrogel (3DNGH) was prepared for the first time and the photocurrent intensity of this material was greatly enhanced, which was attributed to the multiple enhancements accomplished in one step. The porous structure of 3DNGH could provide an exceptionally large accessible surface area, which was beneficial for the anchoring of Ag and TiO2 nanoparticles. The introduction of nitrogen doped graphene and metal nanoparticles was capable to facilitate the charge separation efficiency and accelerate the transfer rate of the photogenerated electron-hole pairs. Then the photoelectrochemical performance was further amplified by the localized surface plasmon resonance of Ag nanoparticles. On the basis of excellent PEC properties of Ag/TiO2/3DNGH, a sensitive label-free PEC sensor has been established for the determination of thrombin successfully. This proposed PEC biosensor exhibited good PEC performances with a wide linear in the range from 0.01p.M. to 10p.M. as well as a relative low detection limit of 3 fM (S/N = 3), indicating that Ag/TiO2/3DNGH would serve as a promising photoactive material in the applications of PEC biosensors.