High performance electrocatalysts supported on graphene based hybrids for polymer electrolyte membrane fuel cells

In this study, new electrocatalysts for PEM fuel cells, based on Pt nanoparticles supported on hybrid carbon support networks comprising reduced graphene oxide (rGO) and carbon black (CB) at varying ratios, were designed and prepared by means of a rapid and efficient microwave-assisted synthesis method. Resultant catalysts were characterized ex-situ for their structure, morphology, electrocatalytic activity. In addition, membrane-electrode assemblies (MEAs) fabricated using resultant electrocatalysts and evaluated in-situ for their fuel cell performance and impedance characteristics. TEM studies showed that Pt nanoparticles were homogeneously decorated on rGO and rGO-CB hybrids while they had bigger size and partially agglomerated distribution on CB. The electrocatalyst, supported on GO-CB hybrid containing 75% GO (HE75), possessed very encouraging results in terms of Pt particle size and dispersion, catalytic activity towards HOR and ORR, and fuel cell performance. The maximum power density of 1090 mW cm^?2 was achieved with MEA (Pt loading of 0.4 mg cm^?2) based on electrocatalyst, HE75. Therefore, the resultant hybrid demonstrated higher Pt utilization with enhanced FC performance output. Our results, revealing excellent attributes of hybrid supported electrocatalysts, can be ascribed to the role of CB preventing rGO sheets from restacking, effectively modifying the array of graphene and providing more available active catalyst sites in the electrocatalyst material.     

A hybrid PEMFC/supercapacitor device with high energy and power densities based on reduced graphene oxide/Nafion/Pt electrode

Proton exchange membrane fuel cells (PEMFCs) possess high energy and low power densities, while supercapacitors are characterized by high power and low energy densities. A hybrid PEMFC/supercapacitor device (HPSD) with high energy and power densities was proposed and fabricated for the first time using a reduced graphene oxide/Nafion/Pt electrode in this study. The reduced graphene oxide (rGO) was a capacitive material, and Pt was used as the electrocatalyst. Nafion ionomers adsorbed onto the rGO sheets surface and connected the rGO sheets and the electrolyte (Nafion membrane), thus increasing the utilization rate and specific capacitance of rGO. During the half-cell tests, the rGO/Nafion/Pt electrode exhibited better pulse discharge and galvanostatic discharge performance than the conventional Nafion/Pt electrode. Due to the unique synergy of electrochemical reaction current and capacitance current during the discharge process, the HPSD exhibited a higher power density (26.2 kW kg⁻¹) than the PEMFC (23.9 kW kg⁻¹). The energy density (12.7 kWh kg⁻¹) exhibited by HPSD was close to that of the PEMFC (13.5 kWh kg⁻¹). Therefore, the concept of HPSD is to create a new method for developing next-generation electrochemical devices with high energy and power densities.     

Efficient electro-oxidation of methanol using PtCo nanocatalysts supported reduced graphene oxide matrix as anode for DMFC

Platinum – cobalt (PtCo) alloy based highly efficient nano electro-catalysts on reduced graphene oxide (rGO) matrix have been synthesized for the electro-oxidation of methanol, by chemical reduction method. Different molar ratio of Pt (IV) and Co (II) ions along with graphene oxide (GO) were reduced using ethylene glycol to obtain PtCo nanoparticles onto rGO sheets (Pt/rGO, PtCo (1:1)/rGO, PtCo (1:5)/rGO, PtCo (1:9)/rGO and PtCo (1:11)/rGO) with 20 wt. % metal and 80 wt. % rGO. The average particle size of PtCo nanoparticles onto rGO support was observed to be 2–5 nm using XRD and TEM analysis. The PtCo (1:9)/rGO nanocomposite catalyst exhibited ～23 times higher anodic current density compare to commercially available Pt/C catalyst (1.68 mA/cm²) for methanol oxidation reaction. The peak power density of 118.4 mW/cm² was obtained for PtCo (1:9)/rGO catalyst in direct methanol fuel cell (DMFC) at 100 °C, 1 bar, and 2 M methanol as anode feed, which is ～3 times higher than that of Pt/C catalyst. The results indicate the potential application of synthesized nanocomposite catalyst in commercial DMFCs.     

Three dimensional assembly of electrocatalytic platinum nanostructures on reduced graphene oxide – An electrochemical approach for high performance catalyst for methanol oxidation

By means of co-electrodeposition, we fabricated 3D assembly of Pt nanostructures with dominant (100) plane on reduced graphene oxide (rGO) modified graphite electrode. The strong metal-support interaction at the atomic level makes the nanostructure highly durable and this modified electrode exhibited high electrocatalytic activity towards methanol oxidation. It has been found that the morphology, active site and the electrochemical activity of Pt are highly dependent on the substrate and the number of electrochemical cycling used for the deposition. rGO-Pt composite deposited using one cycle showed a high mass activity of 2.54 A/mg at 0.67 V for methanol oxidation in acidic condition and 1.84 A/mg at ?0.03 V in alkaline medium. This simple and single step approach using electrodeposition to grow the morphology controlled Pt nanostructure on rGO, will aid in the development of active and stable catalyst for fuel cell applications.     

Polymer-graphene hybride decorated Pt nanoparticles as highly efficient and reusable catalyst for the dehydrogenation of dimethylamine–borane at room temperature

Addressed herein, we report a reduced graphene oxide (rGO) nanosheet coupled with polyaniline (PANI) for platinum (Pt) nanoparticles as supporting materials. The PANI-coupled rGO (PANI@rGO) nanosheet is prepared by a simple one-step chemical assembly strategy, and Pt nanoparticles are anchored on the support of PANI@rGO through the reaction of PANI with a platinum salt. The designed PANI efficiently exposes the surface of rGO sheets and stabilizes metal nanoparticles. Consequently, the Pt@PANI-rGO catalyst exhibits good reusability, durability and high catalytic performance for dimethylamine–borane dehydrogenation reaction. The structure morphology and properties of Pt@PANI-rGO NPs were characterized by using several different techniques such as UV–Vis, XPS, TEM, XRD and HR-TEM-EDX analyses. This newly prepared catalyst can be reused again at low concentrations and temperature. They showed a high turnover frequency (42.94 h^?1) and low E_a value of 15.1 ± 2 kJ/mol for DMAB dehydrocoupling in the ambient conditions. The proposed nano architecture offers a new pathway to promote the performances of rGO in various applications; moreover, this work provides a powerful and universal synthetic strategy for such an architecture.     

Enhanced photoelectrochemical water splitting in hierarchical porous ZnO/Reduced graphene oxide nanocomposite synthesized by sol-gel method

Today the utilization of solar energy to split water and its conversion to hydrogen and oxygen has been considered as a powerful way to solve the environmental crisis. Hierarchical porous nanostructured ZnO and ZnO/reduced graphene oxide (rGO) composite photoanodes are synthesized by innovated sol-gel method using triethylenetetramine (TETA) as a stabilizer. The hierarchical porous ZnO structure containing large agglomerates each consisting of tiny nanoparticles are formed. The X-ray diffraction analysis and Raman spectroscopy confirm the in-situ reduction of graphene oxide sheets during synthesis and formation of ZnO/rGO nanocomposite. Although the band gap and transmittance of the porous nanocomposites do not dramatically change by rGO addition, the main photoluminescence peak quenches entirely showing prolonging exciton lifetime. The ZnO/rGO porous structure achieved remarkably improved current density (1.02 mA cm^?2 at 1.5 V vs. Ag/AgCl) in 1 wt% rGO, up to 12 times higher compared to the bare ZnO (0.09 mA cm^?2 at 1.5 V vs. Ag/AgCl), which attributes to positive role of ZnO hierarchical porous structure and rGO electron separation/transportation. These findings provide new insights into the broad applicability of this methodology for promising future semiconductor/graphene composite in the field of photoelectrochemical water splitting.     

Highly efficient,large surface area and spherically shaped Pt particles deposited electrolytically synthesized graphene for methanol oxidation with impedance spectroscopy

Graphene was synthesized via electrochemical exfoliation technique of graphite rod in Poly (sodium 4-styrenesulfonate) solution. Laser Raman and X-ray Diffraction Spectroscopies were used to confirm the defects and crystal nature of graphene. The surface wettability studies based on water contact angle, further differentiates the affinity of as-prepared graphene and pristine graphite towards water. Modified Glassy carbon (GC) electrodes were prepared by electro-deposition of Platinum (Pt) on bare and graphene coated GC, denoted as GC/Pt and graphene/Pt modified GC respectively. The morphology and chemical composition of the thus synthesized graphene and graphene/Pt modified electrodes were investigated by High resolution transmission electron microscopy, Scanning electron microscopy and Energy dispersive spectroscopy. The electrochemically active surface area of the electro-deposited spherically shaped Pt particles was calculated to be 63.96 m² g^?1 and 25.10 m² g^?1 on graphene/Pt and GC/Pt, respectively. The electro-catalytic performance of modified electrodes for methanol oxidation was envisaged by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. Graphene/Pt modified GC electrode showed higher oxidation peak current (42.90 mA cm^?2) than GC/Pt modified electrode (16.24 mA cm^?2) in forward scan of methanol oxidation because of the uniform distribution of spherically shaped Pt particles on graphene. The reaction path for methanol oxidation at different potentials was elucidated by means of Electrochemical Impedance Spectroscopy.     

Chemically synthesized reduced graphene oxide-carbon black based hybrid catalysts for PEM fuel cells

In this study, hybrid (synthesized rGO and commercial carbon black (CB) in various weight ratios) supported Pt catalysts were synthesized by using the supercritical carbon dioxide deposition (scCO₂) technique for PEM fuel cells. In hybrid materials, rGO to CB weight ratios were changed in between 90:10 to 50:50 which were compared to their plain materials. The physicochemical and the electrochemical characteristics of the materials were examined by using BET, XRD, TGA, TEM, contact angle and roughness measurements, CV and PEM fuel cell performance tests. All these characterizations showed that the hybrid supported Pt catalysts were successfully synthesized. TEM images of the catalysts confirmed the highly dispersed and small nanoparticle formation (1.9–2.9 nm) via scCO₂ deposition technique. Among the hybrid supported catalysts, catalyst having rGO:CB ratio of 70:30 showed the best PEM fuel cell performance. Electrochemical characterization either fuel cell performance test or CV results indicated significantly enhancement in activity with an increase in CB amount in the support.     

Applications of graphene nano-sheets as anode diffusion layers in passive direct methanol fuel cells (DMFC)

The diffusion layer is an important structure in the membrane electrode assembly (MEA) of direct methanol fuel cells (DMFCs) that provide a support layer for catalysts, electronic channels, and gas–liquid mass transport channels. In this study, three types of carbon-based materials were used to fabricate anode diffusion layers – carbon black Vulcan^® (CBV), M-15 grade graphene nanosheets (GM-15) and C-500 grade graphene nanosheets (GC-500). The microporous layers of cathodes were constructed with CBV. A carbon-based microporous layer with a 2 mg cm^?2 loading was coated onto a PTFE-pretreated carbon cloth, while a Nafion-117 membrane was applied as the electrolyte to the DMFCs. Pt–Ru black and Pt black were used as anode and cathode electrode catalysts, each with loadings of 8 mg cm^?2 and 4 mg cm^?2, respectively. All tests were conducted using MEAs with active areas of 4 cm² and air was supplied to single cells by passive modes. Surface morphology was studied using scanning electron microscopy (SEM), which produced pictures of complex network formations within the structures. CBV consists of nanosized carbon particles, while both GM-15 and GC-500 are made of stacks of graphene sheets with flaky structures that increase catalyst utilization. Performance tests of the DMFCs were conducted using a potentiostat that generated polarization curves. The highest peak power density of 13.7 mW cm^?2 was obtained by the GC-500 anode diffusion layer using 3 M methanol as fuel. The energy efficiency of the passive DMFCs was approximately 10% with a specific energy of approximately 610 Wh kg^?1, which is higher than that of conventional lithium-ion batteries, portraying the bright future of alternative energy sources for use in power applications for portable devices. The high power densities obtained by both graphene-based materials, GM-15 and GC-500, demonstrate that graphene is a material other than state of the art carbon black that has the potential to be used as a DMFC anode support material.     

Graphene based catalyst supports for high temperature PEM fuel cell application

In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm² active area single HT-PEMFC with H₂/air at 160 °C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm² for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 °C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H₂/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm² at 160 °C, 175 °C and 190 °C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application.     

The role of Pt loading on reduced graphene oxide support in the polyol synthesis of catalysts for oxygen reduction reaction

Common carbon-blacks have shown insufficient stability as cathodic catalyst supports for proton exchange membrane fuel cells (PEMFCs). In this regard, alternative supports have been proposed and, specifically graphene or reduced graphene oxide (rGO), have attracted special attention. Herein, a set of electrocatalysts using reduced graphene oxide (rGO) as support is synthetized by a modified polyol method. The influence of Pt loading on the support is studied and compared with conventional supports, considering Pt particle morphologies and oxygen reduction reaction (ORR) performance in rotating disk electrode (RDE). Despite Pt average particle size typically increases with the Pt loading, 30 wt% of Pt on rGO is the optimal Pt loading, yielding the highest ORR activity among the rGO-supported electrocatalysts. These results show that both Pt loading and type of support greatly impact on the morphology and electrochemical performance of Pt nanoparticles.     

Nickel-cobalt layered double hydroxide ultrathin nanosheets coated on reduced graphene oxide nonosheets/nickel foam for high performance asymmetric supercapacitors

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett and Teller (BET) and electrochemical techniques such as voltammetry (CV), galvanostatic charge-discharge curves (GCD) and electrochemical impedance spectroscopy (EIS). The resulting electrode which prepared in the presence of CTAB afforded extremely high specific capacitance of 2133.3 F g^?1 at a current density of 4 A g^?1. FE-SEM, TEM and EDS mapping results showed that Ni-Co LDH nanosheets uniformly covered the surface of rGO/NF in the presence of CTAB, and is closely packed and thinner in thickness compared with the sample prepared in similar way without using surfactant. Such new thin and dense morphology facilitates electrolyte ions diffusion through the prepared electrode. A good cycling stability was obtained for the electrode in alkaline media. EIS measurements showed low values of internal resistance (R_s) and charge transfer resistance (R_ct), indicating that the prepared nanocomposite is a promising candidate for supercapacitor applications. The asymmetric supercapacitor (ASC) based on the Ni-Co LDH/CTAB/rGO/NF as a positive electrode and rGO/NF as a negative electrode was assembled and it exhibited a C_s of 71.4 F g^?1 at a current density of 2 A/g and correspondingly energy density of as high as 68 Wh kg^?1.     

Reduced graphene oxide-supported nickel oxide catalyst with improved CO tolerance for formic acid electrooxidation

The superior catalytic activity along with improved CO tolerance for formic acid electrooxidation has been demonstrated on a NiO-decorated reduced graphene oxide (rGO) catalyst. The cyclic voltammetry response of rGO–NiO/Pt catalyst elucidates improved CO tolerance and follows direct oxidation pathway. It is probably due to the bene?cial effect of residual oxygen groups on rGO support which is supported by FT-IR spectrum. A strong interaction of rGO support with NiO nanoparticles facilitates the removal of CO from the catalyst surface. The chronoamperometric response indicates a higher catalytic activity and stability of rGO–NiO/Pt catalyst than the NiO/Pt and unmodified Pt electrode catalyst for a prolonged time of continuous oxidation of formic acid.     

All‐carbon hybrids for high performance supercapacitors

A hybrid nanostructure with partially reduced graphene oxide (rGO) and carbon nanofibers (CNFs) was fabricated and used as supercapacitor electrodes. A straightforward, environmentally friendly, and low‐cost microwave‐assisted reduction process was developed for the synthesis of rGO/CNF hybrid structures. The fabricated supercapacitor devices showed a specific capacitance of 95.3 F g^?1 and a superior long‐term cycling stability. A capacitance retention of more than 97% after 11 000 galvanostatic charge discharge cycles was obtained. These and other results reported in this paper indicate that high‐rate, all‐carbon, rGO/CNF hybrid nanostructures are highly promising supercapacitor electrode materials.     

Enhanced hydrogen evolution performance by covalent-linked ultrafine,uniform Pt nanoparticles with doped sulfur atoms in three-dimensional graphene

Highly efficient and stable electrocatalyst for hydrogen evolution reaction (HER) is essential for the application of green hydrogen energy. To date, platinum -based materials are the most efficient electrocatalyst. Developing inexpensive electrocatalyst with low Pt loading and high platinum utilization efficiency is one of effective strategies to lower the cost of platinum -based electrocatalyst. In this paper, it was demonstrated that ultrafine and uniform distribution platinum nanoparticles could be synthesized on three-dimensional sulfur-doped graphene materials (Pt/3DSG) via covalent cross-linking between platinum and doped sulfur atoms. The high conductive 3DSG not only facilitates the electron transport but also serves as a template for depositing ultrafine and uniform platinum nanoparticles. The Pt/3DSG with low Pt loading (3.1 wt%) delivers extremely outstanding HER performance, which is superior to the commercial 20 wt% Pt/C catalyst. The turnover frequencies (TOFs) of Pt/3DSG can reach 1.12 s^?1, which is larger than that of 20% Pt/C (0.71 s^?1). Furthermore, the stability is also superior than that of Pt/C. This work provides a rational design strategy for highly efficient and stable electrocatalysts with low loading and high utilization of precious metal.     

Highly efficient and durable phosphine reduced iron-doped tungsten oxide/reduced graphene oxide nanocomposites for the hydrogen evolution reaction

The design and development of inexpensive and highly efficient electrocatalysts for hydrogen production from water splitting are highly crucial for green energy and the hydrogen economy. Herein, we report phosphine reduced an iron-doped tungsten oxide nanoplate/reduced graphene oxide nanocomposite (Fe-WOxP/rGO) as an excellent electrocatalyst for the hydrogen evolution reaction. This electrocatalyst was synthesized using a hydrothermal method, followed by reduction with phosphine (PH₃), which was generated from sodium hypophosphite. The catalyst onset potential, Tafel slope, and stability were investigated. Accordingly, Fe-WOxP/rGO exhibited impressively high electrocatalytic activity with a low overpotential of 54.60 mV, which is required to achieve a current density of 10 mAcm^?2. The Tafel slope of 41.99 mV dec^?1and the linear sweep voltammetry curve is almost the same as 2000 cycles and electrolysis under static overpotential (54.60 mV) is remain for more than 24 h in 0.5 M H₂SO₄. The catalytic activity and conductivity of Fe-WOxP/rGO were higher than WO_XP, Fe-WOxP and WOxP/rGO. Such an outstanding performance of the Fe-WOxP/rGO nanocomposite is attributed to the coupled synergic effect between high oxygen vacancies formation on tungsten oxide in the nanoplate-like structure of Fe-WOxP and rGO nanosheet, making it as an excellent electrocatalyst for hydrogen evolution reaction.     

AuNi alloy nanoparticles supported on reduced graphene oxide as highly efficient electrocatalysts for hydrogen evolution and oxygen reduction reactions

Bimetallic nanoparticles of Au and Ni in the form of alloy nanostructures with varying Ni content are synthesized on reduced graphene oxide (rGO) sheets via a simple solution chemistry route and tested as electrocatalysts towards the hydrogen evolution (HE) and oxygen reduction (OR) reactions using polarization and impedance studies. The AuNi alloy NPs/rGO nanocomposites display excellent electrocatalytic activity which is found to improve with increasing Ni content in the AuNi/rGO alloy nanocomposites. For HER, the best AuNi alloy NPs/rGO electrocatalyst, the one with the highest Ni content, exhibits high activity with an onset overpotential approaching zero versus the reversible hydrogen electrode and an overpotential of only 37 mV at 10 mA cm^?2. Additionally, a low Tafel slope of 33 mV dec^?1 and a high exchange current density of 0.6 mA cm^?2 are measured which are very close to those of commercial Pt/C catalyst. Also, in the ORR tests, this electrocatalyst displays comparable activity to Pt/C. The Koutecky–Levich plots referred to a 4-electron mechanism for the reduction of dissolved O₂ on the AuNi alloy NPs/rGO catalyst. The electrocatalyst thus demonstrates excellent activity towards HER and ORR. Additionally, it exhibits outstanding operational durability and activation after 10,000^th cycles assuring its practical applicability.     

High electrocatalytic performance of a graphene-supported PtAu nanoalloy for methanol oxidation

Homogeneously distributed PtAu nanoalloy anchored to graphene (PtAuNA/G) was synthesized via a simple one-step electrochemical deposition process, in which Pt and Au ions and graphene oxide was simultaneously electro-reduced on the glassy carbon electrode. The morphology evolution of PtAuNA/G synthesized with different deposition times was characterized via field-emission scanning electron microscopy. X-ray diffraction and transmission electron microscopy was applied to confirm the alloy structure. The electrodeposition conditions, including the deposition time, were further optimized to explore the morphological evolution of PtAuNA/G. Based on cyclic voltammetry and chronoamperometry results, it was found that PtAuNA/G can efficiently catalyze the oxidation of methanol in alkaline media with dramatically enhanced electrocatalytic activity (7.268 mA cm^?2, 3.83 times higher than that of commercial carbon-supported Pt nanoparticles, 1.894 mA cm^?2), along with a considerably improved tolerance to poisoning (current decline: 69% vs 99.89%). These results indicate a great potential for PtAuNA/G in fabricating high-performance direct methanol fuel cells.     

3-D structured Pt/rGO-polyethyleneimine-functionalized MWCNTs prepared with different mass ratio of rGO and MWCNT for proton exchange membrane fuel cell

Various 3-D structured Pt/xrGO-yPolyethyleneimine-functionalized MWCNTs (PMWCNT) were successfully prepared by the hybridization of rGO and PMWCNT. The FE-SEM and TEM images confirm the 3-D structure of hybridized Pt/rGO-PMWCNT catalyst and dispersion of Pt nanoparticles. In case of Pt/PMWCNT, Pt nanoparticles are preferentially deposited onto the external surface of PMWCNT but upon hybridization, the preferential deposit of Pt nanoparticles onto PMWCNT is not expected due to high affinity of rGO toward Pt nanoparticles. The Pt content deposited onto the hybridized supporting materials tends to be increased with rGO content. It is noteworthy that the BET surface area is increased with PMWCNT content due to the formation of the 3-D structure. The electrochemical active surface area (ECSA) and durability based on ECSA is also affected by the mass ratio of rGO and PMWCNT, exhibiting the highest ECSA of 32.5 m²/g and the least reduction of ECSA after 1200 cycle by Pt/1rGO-1PMWCNT. The cell performance is enhanced by the hybridization with the best cell performance by Pt/1rGO-1PMWCNT. It is, therefore, desirable to choose the appropriate mass ratio of rGO and PMWCNT to maximize the electrochemical properties.     

Planar solid-state amperometric hydrogen gas sensor based on Nafion®/Pt/nano-structured polyaniline/Au/Al2O3 electrode

The effects of Nafion^® film thickness and charges passed for the preparation of Pt and nano-structured polyaniline (nsPANi) on the sensing properties of a planar solid-state amperometric hydrogen gas sensor are investigated. The surface morphology, Pt loading and electroactive surface area (ESA) are analyzed by FESEM, inductively coupled plasma (ICP) and cyclic voltammetry (CV), respectively. The specific sensitivity of the hydrogen gas sensor can be effectively promoted by decreasing the thickness of the Nafion^® film and the charge passed for the electrodeposition of Pt and PANi (from 30 to 10 mC), respectively. The very low Pt loading of the sensing composite electrode is due to the use of the nanofibrous PANi as support, which remarkably promotes Pt utilization. The specific sensitivity and the response time of the hydrogen gas sensor based on the Nafion^® (5.7 μm)/Pt/nsPANi/Au/Al₂O₃ electrode with a Pt loading of 1.87 μg are found to be 338.50 μA ppm^?1 g^?1 and 100–250 s, respectively, for measuring 10–10,000 ppm H₂.