High-temperature Thermal Reduction Research Articles

Ambient Deposition of Single Atoms for Enhancement of Nanostructured Metal Oxide Electrode Catalytic Performance

Single-atom decoration represents cutting-edge technology for enhancing heterogeneous catalysis by utilizing the unique capabilities of catalysts at the atomic level. However, the high surface energy of single atoms often causes them to aggregate, forming nanoparticles [1]. To address this challenge, we first modify the surface structure by synthesizing nanostructured support layers, such as TiO2 nanotubes, TiO2 nanosheets, and NiO nanosponge. Especially TiO2 nanotubes and NiO nanosponge pose relevant support layers due to their favorable attributes, including a high surface-to-volume ratio, abundance, and excellent chemical stability, while TiO2 nanosheets serve as model system. Vertically aligned, well-ordered, self-organized oxide nanostructures can be conveniently fabricated through anodization, allowing precise control over the geometry of the nanotubes and nanopores [2,3]. Well-defined atomic-scale defects on the surface of the supports are generated to immobilize single-atom co-catalysts. Therefore, defect engineering techniques typically require high-temperature thermal reduction. We present more gentle defect-engineering approaches, including room-temperature sonochemical treatment or UV-light irradiation. By combining these approaches, we are able to effectively trap Pt and Ir single atoms.We present a direct method utilizing UV-light radiation to induce point defects, specifically Ti3+ and oxygen vacancies (VO) onto the surface of TiO2 nanosheets and efficiently decorate them with Pt single atoms [4]. Our findings demonstrate that sonochemically treated TiO2 nanotubes provide a remarkable substrate for single-atom decoration from dilute solutions, resulting in promising performance in H2 evolution catalysis and renewable energy conversion. Additionally, the role of V single-atom decoration in ultrasonic treatment of support materials is investigated.Thermal annealing in a reductive atmosphere induces the formation of numerous defects, facilitating the anchoring of single Ir atoms onto the surface of annealed NiO nanostructures. Additionally, the novel ultrasound-driven method stabilizes these Ir atoms within the porous structure. By employing both approaches, we effectively trap Ir single atoms, thereby enhancing the efficiency of the oxygen evolution reaction in electrocatalysis [5].The characterization of the electrodes is conducted using microscopy techniques (FESEM, TEM, and HAADF-STEM) and spectroscopy (XPS and ToF-SIMS) [6]. Gas chromatography is employed to evaluate the H2 photocatalytic performance of TiO2 electrodes, while linear sweep voltammetry is utilized to assess the H2 and O2 electrochemical activity of NiO electrodes [5]. Our findings highlight the significant enhancement of photo- and electrocatalytic efficiency of nanostructured oxide electrodes modified with highly stable single-atom co-catalysts by gentle treatments.

Applicability of Non-PGM Bi-Functional Electrocatalyst in a Scaled-up Anion Exchange Membrane Water Electrolysis

While non-precious metal catalyst materials are crucial for AEMWE systems, catalyst substances possessing both adequate hydrogen molecule adsorption ability and suitable electrical conductivity and hydrophilicity are still in the developmental stage.Ni-Mo alloy metals are known as those that have appropriate hydrogen molecule adsorption binding energy, making them excellent electrochemical catalysts for the cathode. However, they suffer from a high content of oxide, which hampers electrical conductivity, and the formation of a high oxidation state of Ni molecules, making hydrogen molecule detachment challenging.On the other hand, Ni-Fe alloys are recognized for their excellent -OOH group adsorption ability and high electrical conductivity, and that has a low oxidation state Ni phase for high hydrogen desorption ability.Therefore, in this study, we aimed to synthesize NiMoFe-based alloy catalysts to enhance the hydrogen evolution reaction (HER) activity of Ni-Mo group catalysts while simultaneously increasing the oxygen evolution reaction (OER) activity. Using a hydrothermal synthesis method for NiMoFe catalysts we employed a high-temperature thermal reduction process to minimize the oxide layer that has poor conductivity.Evaluation of the catalyst activity through half-cell experiments demonstrated low overpotentials in both Overall water electrolysis reactions. Furthermore, an MEA-type experiment was conducted to evaluate the applicability of single-cell.Furthermore, Stability tests confirmed a stable voltage.Finally, when compared to the combination of precious metal catalysts, this exhibited superior performance. Therefore, this study suggests that non-noble catalysts could serve as a crucial stepping stone, surpassing PGM metal catalysts in alkaline media.

High Potential Electrochemical Synthesis of Thermally Reduced Graphene Nanomaterial

In this study, we provide electrochemical techniques for synthesizing thermally reduced graphene nanomaterial that have high potential, low defects, cost-effectiveness, and ecological sustainability. The electrochemical exfoliation is carried out by employing a 195 W DC (voltage = 60[Formula: see text]V and current = 3.25 A) power source at a maximum electrolyte temperature of about 92.5∘C within the aqueous suspension of 2[Formula: see text]M of sulfuric acid (H2SO[Formula: see text]. Thereafter, the synthesized nanomaterial was treated in the weak piranha [combination of sulfuric acid and hydrogen peroxide (H2O[Formula: see text]] solution using an electrochemical technique inside the water bath sonicator at 80∘C. X-ray diffraction (XRD) analysis shows the peak of diffraction to the (002) plane of the reduced graphene oxide (RGO) samples emerges at around 2[Formula: see text] and 26.56∘ with an interplanar distance of 3.40 Å and 3.54 Å. According to the XRD data, after the high-temperature thermal reduction phase, the structure of the crystals and interplanar separation were recovered. The size of the crystallite of RGO produced under H2SO4 conditions was discovered to be greater than the crystallite size of graphene oxide produced under piranha solution conditions. The Raman analysis results show that the degree of disorder of the graphene synthesized within the H2O2 was higher than in comparison to the graphene synthesized in H2SO4. Field emission scanning electron microscopy (FE-SEM) results show that graphene synthesized in the presence of H2O2 has a thin and porous microstructure in comparison to H2SO4 with no significant effect on the presence of the availability of the C/O ratio. The atomic force microscopy (AFM) analysis indicates that the surface roughness of the graphene synthesized in the H2O2 was higher than that of the H2SO4. The Fourier transform infrared spectroscopy (FT-IR spectroscopy) analytical results show that the majority of the functional groups have been eliminated within the samples.

Regulating the Cu2Se-SnO nanosheet heterostructure interface for efficient CO2 conversion to tunable syngas ratios

Electrocatalytic conversion of CO2 to syngas is an attractive pathway for transforming CO2 into high-value chemicals, but the process still suffers from low selectivity. In our work, we construct a two-dimensional (2D) structure of Cu2Se-SnO heterojunction catalyst through a high-temperature thermal reduction method. The catalyst with two phases located in the same plane exhibits efficient charge transfer, and the tunable heterojunction interface acts as active sites for CO2 adsorption and activation. Additionally, its suitable *CO adsorption energy facilitates the desorption of intermediates, leading to the formation of CO. Finally, this catalyst demonstrates excellent selectivity for syngas, maintaining a Faradaic efficiency (FE) of over 60% across a wide range of potentials (-0.67 ∼ −1.07 V vs. RHE) with adjustable syngas ratios and up to 92% FE at −0.97 V vs. RHE. This research provides a new approach for balancing reduction CO2 and competing hydrogen evolution reaction.

In Situ Preparation of rGO-Cement Using Thermal Reduction Method and Performance Study.

In this study, the combination of freeze-drying and high-temperature thermal reduction methods was employed to in situ prepare reduced graphene oxide (rGO)-Cement based on graphene oxide (GO)-Cement. The electrical conductivity and mechanical properties of the rGO-Cement were investigated. Microscopic analysis methods such as Raman spectra, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to confirm the successful transformation of GO-Cement to rGO-Cement. The research results demonstrated that with an increase in rGO content, the electrical resistivity of the rGO-Cement decreased first and then increased, reaching a percolation threshold at the dosage of 0.7 wt.%. The compressive strength and flexural strength of the rGO-Cement increased first and then decreased. The optimal dosage of rGO was 0.7%. The in situ preparation of rGO-Cement using the thermal reduction method holds a great potential for various applications, providing new ideas and methods for the modification and enhancement of cement materials.

Effects of high-temperature thermal reduction on thermal conductivity of reduced graphene oxide polymer composites

The graphitic crystalline structure of reduced graphene oxide (rGO) can be improved by high-temperature thermal reduction at various heat-treatment temperatures ranging from 1000 to 2500 °C. The crystallinity significantly increased with increasing heat-treatment temperature. The electrical conductivities of the rGOs heat-treated at 2000 and 2500 °C (h-rGO-2000 and h-rGO-2500, respectively) were similar to those of commercial graphite. The isotropic thermal conductivity of rGO/epoxy composite with 10 wt% h-rGO-2500 (2.56 W/mK) was 11.6 times higher than that of pristine rGO (p-rGO; 0.22 W/mK) and significantly superior to those of epoxy composites with commercial graphite (0.82 W/mK) and mesophase pitch-based carbon fibers (MPCFs; 1.29 W/mK). Moreover, owing to the synergistic effect operating in the MPCF–h-rGO hybrid filler in epoxy composites, this combination of fillers increased the thermal conductivity to a greater extent than the MPCF–p-rGO hybrid filler. Optimum synergistic effects on the isotropic and in-plane thermal conductivities were achieved with an MPCF:h-rGO-2000 weight ratio of 49:1 (11.90 and 17.93 W/mK, 1.48 and 1.85 times higher than 8.02 and 9.69 W/mK for MPCF–p-rGO, respectively). Finally, a machine learning method that could predict and optimize the properties of rGOs based on their heat-treatment temperatures and material compositions was developed.

Electrochemical Exfoliation and Thermal Deoxygenation of Pristine Graphene for Various Industrial Applications

The transition of graphene from the lab to consumer goods is still a challenging job that necessitates efficient and cost-effective large-scale graphene production. This study combines electrochemical exfoliation in an aqueous solution of sulfuric acid (1M H2SO[Formula: see text] and hydrogen peroxide (3% H2O[Formula: see text] followed by thermal deoxygenation at a temperature of 800[Formula: see text]C within the ambient environment. This method allows the inexpensive synthesis of pristine graphene for various industrial applications. X-Ray diffraction (XRD) results for pristine graphene showed a distinct peak at 2[Formula: see text] with a corresponding interplanar distance ([Formula: see text] of 3.3754 Å and a crystallite size of 18 nm. XRD statistics indicated that the crystal structure of the original graphene was preserved. The crystalline structure was recovered and the interplaner distance was decreased following the high temperature thermal reduction. According to Raman spectroscopy, the impurity degree (I[Formula: see text]/I[Formula: see text] region fraction of pristine graphene was 0.211. This indicates that the original graph produced by the current method has little distortion. Raman analysis shows that there is a linear red shift in peaks D-band (D), G-band (G), and second order of the D-band (2D) due to the increase in phonon–phonon nonlinear interactions with increasing temperature, so that peaks (D), (G) and (2D) shifts are shown. The majority of the functional groups were discovered to be eliminated after high temperature thermal treatment. The three-dimensional graphene sheet is highly defined and intricately coupled in the microstructure analysis, resulting in a laxer and porous structure. When treated at a temperature below 800[Formula: see text]C, there was only minor damage to the reduced graphene oxide (RGO) microstructure. The results of the Atom Force Microscope (AFM) demonstrated that the flaws spread over time from the layer boundaries and pores to the edges and eventually resulted in a separate RGO archipelago. According to TGA analysis, at temperatures up to 800[Formula: see text]C, the RGO sheet loses up to 45% of its weight.

Room-temperature defect-engineered titania: An efficient platform for Pt single atom decoration for photocatalytic H2 evolution

Single-atom (SA) decoration represents the forefront of technological advancements in heterogeneous catalysis, harnessing the exceptional performance of catalysts at the atomic level. However, the high surface energy of isolated atoms often leads to agglomeration, resulting in the formation of nanoparticles. To address this challenge, trapping single atoms within surface defects has emerged as an effective strategy for atom immobilization. Conventional defect engineering techniques, such as high-temperature thermal reduction, suffer from adverse effects, such as sintering of the support material. In this study, we introduce a novel and facile room-temperature sonochemical method to induce well-defined atomic-scale defects on the surface of highly active TiO2 nanosheets, predominantly exposing the (001) facet. By introducing a highly diluted Pt precursor to the ultrasonicated nanosheet slurry, isolated Pt atoms were selectively trapped within freshly formed defects. Remarkably, the resulting Pt single atom decorated samples exhibit a striking 100-fold increase in photocatalytic H2 evolution compared to pristine TiO2 nanosheets. Notably, we demonstrate that the density of the generated defects and the loading of Pt single atoms can be precisely tailored by adjusting the sonication time. Atomic-scale characterization, complemented by density functional theory (DFT) calculations, provides compelling evidence of the strong bonding between Pt single atoms and the defects generated via sonochemical treatment. Our findings offer a promising approach for defect engineering and SA decoration on a larger scale, underscoring the significant potential of this room-temperature technique for heterogeneous catalysis.

Quantifying Electrochemical Driving Force for Exsolution in Perovskite Oxides by Designing Graded Oxygen Chemical Potential.

Metal nanoparticles exsolved and anchored at the parent perovskite oxide surfaces can greatly enhance the activity and antisintering stability for high-temperature (electro-) chemical catalytic reactions. While exsolution of nanoparticles triggered by using conventional high-temperature thermal reduction suffers from slow kinetics, using an electrochemical driving force can promote the exsolution rate. However, a quantitative correlation between the applied electrochemical driving force and the spatial density of exsolved nanoparticles remains unknown. In this work, we use a specially designed electrochemical device to induce a spatially graded voltage in a La0.43Ca0.37Ti0.94Ni0.06O3-δ electrode, in order to systematically investigate the effect of electrochemical switching on exsolution. With increasing driving force, which leads to decreasing oxygen chemical potential, the density of nanoparticles was observed to increase dramatically, while the average particle size remained roughly constant. We further identified oxygen vacancy pairs or clusters as the preferential nucleation sites for exsolution. Our work provided a high-throughput platform for the systematic study of exsolution of perovskite oxides targeted for fuel electrode materials with improved electrocatalytic performance and stability.

Preparation and tribological properties of Phenyl-Functionalized thermally reduced GrapheneOxide

We report a two-step method for preparing hydrophobic graphene. This method transforms graphite oxide (GO) into thermally reduced graphene oxide (TRGO) and then into phenyl-functionalized thermally reduced graphene oxide (PTRGO) through high-temperature thermal reduction and a heat-induced solid-phase chemical reaction. GO was successfully stripped, and TRGO was prepared by high-temperature thermal reduction. The phenyl radicals produced by the thermal decomposition of benzoyl peroxide(BPO) preferentially induced the ring-opening of the epoxy group on the TRGO, and the phenyl groups were attached. The prepared PTRGO displayed excellent hydrophobic properties, with a water contact angle of 132.0°, and was stably dispersed in the base oil without requiring any surfactants or modifiers. Four-ball testing showed that when the additive amount of PTRGO was 75 mg/L, the coefficient of friction (COF) and wear scratch diameter (WSD) of Abu Dhabi (AD) base oil (150 N) decreased by 24.2% and 15.7%, respectively.

Porous polymer cement composites for quasi-solid graphene supercapacitors

We reported a strong and cheap polymer modified Portland cement (PC) composites with interconnected pores as solid electrolyte for graphene supercapacitors. The porous polymer cement composites solved the low ionic conductivity question of construction materials. Herein, the effects of PAA molecular weight, PAA content and curing age on electrical energy storage and mechanical property were investigated in detail. The PAA (Mw = 5000)/PC-5 % sample delivers the best multifunctionality. Moreover, the as-assembled solid supercapacitor exhibits an optimum energy density of 15.93 mW h cm−2, as well as a considerable compressive strength of 16.2 MPa at 28 days. In addition, introducing PAA can result in high porosity which is conductive to ion migration. The symmetric electrode is directly loaded with GO on Ni foam by electrophoretic, followed by high temperature thermal reduction. The integrated solid supercapacitors are effective, holistic and effortless to operate at room temperature, and they exert a crucial role in energy storage field of inorganic building materials application.

Impact of high temperature thermal reduction on microstructure, crystallinity and surface topography of reduced graphene oxide

Impact of high temperature thermal reduction on microstructure, crystallinity and surface topography of reduced graphene oxide

Facile and scalable preparation of ultralight cobalt@graphene aerogel microspheres with strong and wide bandwidth microwave absorption

Cobalt@graphene aerogel microspheres (GCoAMs) with tunable porous structures are fabricated by using a unique spraying and crosslinking coagulation method. The graphene oxide (GO) and sodium alginate (SA) mixture aqueous dispersions were used for spraying. The cross-linking reaction occurs quickly between the carboxylic group of SA in the sprayed microdroplets and metal Co2+ in the collector bath, which fixes the microsphere shape and in-situ immobilizes the metal ion. After freeze-drying and the subsequent high-temperature thermal reduction, the ultralight GCoAMs are obtained. The pore structures of GCoAMs can be controlled by varying the GO/SA ratio. The GCoAMs exhibit strong and wide broadband microwave absorption due to its hierarchical porous structures and graphene/metal Co hybrid composition. At a GCoAMs loading content of 1.5 wt%, the minimal reflection loss reaches as high as −70.4 dB with a thin specimen thickness of 2.2 mm at 13.18 GHz and its effective absorption band achieves 5.65 GHz with a specimen thickness of 1.98 mm. At 2 wt% GCoAMs, the effective absorption band achieves 6.09 GHz with a specimen thickness of 2 mm, covering the whole Ku band. This work provides a novel, low-cost and easily scale-up method for preparing the lightweight and efficient microwave absorbers, which could be used in microwave telecommunication fields.

In-situ synthesis of phosphorus-doped graphene paper with adenosine triphosphate and its application for intelligent fire warning

Design of intelligent sensors for detecting early fire warning before combustion is a challenging for the fire safety. Herein, a nacre-biomimetic paper based on graphene oxide (GO) and adenosine triphosphate (ATP) was fabricated via a low-temperature evaporation assembly approach. Then the fire-alarm sensor was designed according to the high temperature thermal reduction properties of GO. The GO-ATP paper exhibited a well-organized ‘‘brick and mortar” structure due to the presence of hydrogen bonds and electrostatic attraction interaction between GO and ATP molecules. The paper containing 50 wt% of ATP presented a rapid flame detection response (1.36 s) and a long continuous alarm time (1300 s) due to in-situ phosphorus doping and the honeycomb-like char forming during fire exposure. Moreover, the GO-ATP-50 also exhibited flexibility, flame retardant performance, heat insulation ability and char-forming properties. This work provides a bright application prospect for fire safety and prevention of combustible materials.

The Spin Modulation Stimulated Efficient Electrocatalytic Oxygen Evolution Reaction over LaCoO3 Perovskite.

Perovskite is a promising non-noble catalyst and has been widely investigated for the electrochemical oxygen evolution reaction (OER). However, there is still serious lack of valid approaches to further enhance their catalytic performance. Herein, we propose a spin state modulation strategy to improve the OER electrocatalytic activity of typical perovskite material of LaCoO3 . Specifically, the electronic configuration transition was realized by a simple high temperature thermal reduction process. M-H hysteresis loop results reveal that the reduction treatment can produce more unpaired electrons in 3d orbit by promoting the electron transitions of Co from low spin state to high spin state, and thus lead to the increase of the spin polarization. Electrochemical measurements show that the catalytic performance of LaCoO3 is strongly dependent on its electronic configuration. With the optimized reduction treatment, the overpotential for the OER process in 0.5 M KOH electrolyte solution at 10 mA cm-2 current density was 396 mV, significantly lower than that of the original state. Furthermore, it can mediate efficient OER with an overpotential of 383 mV under an external magnetic field, which is attributed to the appropriate electron filling. Our results show that electron spin state regulation is a new way to boost the OER electrocatalytic activity.

Hydrogen absorption-desorption cycle decay mechanism of palladium nanoparticle decorated nitrogen doped graphene

As a hydrogen storage material, palladium nanoparticle decorated nitrogen doped graphene (Pd/N-rGO) has drawn much attention owing to its high absorption capacity at moderate conditions. However, its hydrogen absorption-desorption cycle performance, which is essential for their practical application, has been rarely studied. In this paper, a simple and convenient high temperature thermal reduction method was used to synthesize nitrogen-doped graphene decorated with Pd nanoparticles (Pd/N-rGO). Taken it as a representative, the hydrogen absorption-desorption cycle performance of Pd/N-rGO was investigated. The results showed that after three cycles the hydrogen storage capacity dropped from 2.9 ​wt% to 0.8 ​wt% at 25 ​°C and 4 ​MPa pressure. It was found that the palladium nanoparticles shed from Pd/N-RGO sheet after cycle performance test, and then agglomerated. These phenomena will weaken the hydrogen spillover effect, leading to the decrease of hydrogen storage capacity. Meanwhile, decreased defects reduce the hydrogen absorption sites, which will thus deteriorate the hydrogen storage capacity.

One-pot synthesis of pre-reduced graphene oxide for efficient production of high-quality reduced graphene oxide and its lithium storage application

Graphene oxide (GO) is the key for the large-scale production of graphene by chemical oxidation-thermal reduction route. However, the current synthesis methods of GO involve concentrated sulfuric acid and potassium permanganate, which poses a risk of explosion and potential environmental pollution. Furthermore, a large number of oxygen-containing functional groups cause GO sheets to swell, posing a major challenge to the purification process. In this paper, a one-pot hydrothermal method is developed to synthesize pre-reduced graphene oxide (PRGO). The precursor is then employed to produce reduced graphene oxide (RGO) by further high-temperature thermal reduction. It not only avoids the complex temperature control and dilution operations during the oxidation and exfoliation processes but also enables the recycling of sulfuric acid. The synthesized weakly hydrophilic PRGO is highly conducive to achieve rapid filtration, which simplifies the purification process. The obtained reduced graphene oxide exhibits high rate capability and stable long cycling performance as the anode of lithium-ion batteries. This simple, safe and green synthesis route paves the way to large-scale preparation of graphene and its application for Li-ion storage.

Synthesis of Cu2O-Modified Reduced Graphene Oxide for NO2 Sensors.

Nowadays, metal oxide semiconductors (MOS)-reduced graphene oxide (rGO) nanocomposites have attracted significant research attention for gas sensing applications. Herein, a novel composite material is synthesized by combining two p-type semiconductors, i.e., Cu2O and rGO, and a p-p-type gas sensor is assembled for NO2 detection. Briefly, polypyrrole-coated cuprous oxide nanowires (PPy/Cu2O) are prepared via hydrothermal method and combined with graphene oxide (GO). Then, the nanocomposite (rGO/PPy/Cu2O) is obtained by using high-temperature thermal reduction under Ar atmosphere. The results reveal that the as-prepared rGO/PPy/Cu2O nanocomposite exhibits a maximum NO2 response of 42.5% and is capable of detecting NO2 at a low concentration of 200 ppb. Overall, the as-prepared rGO/PPy/Cu2O nanocomposite demonstrates excellent sensitivity, reversibility, repeatability, and selectivity for NO2 sensing applications.

Converting spent lithium cobalt oxide battery cathode materials into high-value products via a mechanochemical extraction and thermal reduction route

This study innovatively combines mechanochemistry and high-temperature thermal reduction to achieve the recovery of valuable metals from spent LIBs. First, under the action of mechanical force, the crystal structure of lithium cobalt oxide (LiCoO2) found in the cathode materials of spent LIBs was destroyed and converted into lithium carbonate (Li2CO3) and Li-free residue (C/Co3O4) using dry ice as a co-grinding reagent. The optimum Li2CO3 recovery conditions were determined to be as follows: a ratio of dry ice: LiCoO2 powder mass of 20:1; a rotation speed of 700 rpm, and a reaction time of 1.5 h. With these conditions the maximum percentage of Li2CO3 recovered was 95.04 wt%. The Co3O4 in Li-free residue was reduced to a high-value Co0 product via a high-temperature (800 °C) heat treatment. Gibbs free energy analysis confirmed that the carbon in the Li-free residue could be used as a self-reducing reagent for the thermal reduction of Co3O4. The reactants and products of each step were characterized by XRD, FT-IR, XPS and SEM techniques. The green route for recycling spent LIBs that this study proposes realizes the green and cost-effective conversion of LiCoO2 to high-value products, which may become an outstanding example of recycling spent LIBs.

Nacre-biomimetic graphene oxide paper intercalated by phytic acid and its ultrafast fire-alarm application

A novel nacre-like flame-retardant paper based on graphene oxide (GO), and phytic acid (PTA) is fabricated via evaporation-induced self-assembly. This facile method is time saving and low energy consuming. A facile approach is proposed to improve thermal oxidative stability of GO paper by in situ phosphorus doping during flame exposure. Then fire-alarm system is designed based on the high-temperature thermal reduction characteristic of GO. The GO paper functionalized with PTA (GO-PTA) can provide ultrasensitive, reliable and longtime fire early-warning signal. Fire alarm can be triggered at approximately 0.50 s when GO-PTA samples are attacked by fire. Phosphorus atoms are in situ doped into graphene layers during fire exposure, endowing GO-PTA paper with outstanding thermal oxidative stability, and thus alarm duration time of GO is greatly improved. The work develops advanced fire detection and early-warning sensors that provide reliable and continuous signals, which provide more available time for fire evacuation.