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In the present study, physically crosslinked polyvinyl alcohol and tetraethyl orthosilicate (PVA-TEOS/PT) composite membrane doped by NaOH was used synthesized to enhance the performance of an alkaline direct sodium borohydride fuel cell (DSBFC) for the first time. The PVA-TEOS (PT) solution was subjected to varying number of freeze-thaw cycle and doped with varying concentration of NaOH for further characterization and performance evaluation in DSBFC. The physical crosslinking increased the amorphous nature of the membrane electrolyte and hence, the ionic conductivity improved significantly. The amount of TEOS in PVA matrix was varied from 5 wt % to 15 wt %. The highest ionic conductivity of 9.67 ± 0.04 × 10−3 S cm−1 was obtained for the membrane freeze-thawed of cycle 7 having 10 wt % of TEOS and dipped in 4 M NaOH solution (PT 10 wt% -7Cy-(4 M)). The physically crosslinked NaOH doped PVA-TEOS composites were tested in a single DSBFC using the Pt (40 wt %)/C at anode and cathode both. The fuel NaBH 4 mixed with supporting electrolyte NaOH was used at anode and pure oxygen was used as oxidant at cathode. The membrane electrolyte (PT 10 wt% -7Cy-(4 M)) with highest conductivity of 9.67 ± 0.04 × 10−3 S cm−1 exhibited highest peak power/maximum power density of 85.19 mW/cm2 at a current density of 184 mA/cm2 at the temperature of 60 °C. The recorded highest power density (85.19 mW/cm2) was capable to run array of LED light (1.2 W) for at least 12 h without any fall in performance. [Display omitted] • Physical crosslinking by freeze-thaw enhanced interaction between PVA and TEOS. • Number of freeze-thaw cycle affects the ionic conductivity of PT membrane. • Wt % of TEOS in the PVA control the ionic conductivity of PT membrane. • PT 10 wt% -7Cy-(4 M) membrane electrolyte exhibited highest ionic conductivity. • PT 10 wt% -7Cy-(4 M) produced highest power density of 84.19 mW/cm2 in DSBFC. [ABSTRACT FROM AUTHOR]

In the present work, glycerol‐based air breathing microfluidic fuel cell (μFC) is investigated. The noble metal Pd and non‐noble metal Ni‐based bimetallic synthesized electrocatalyst (Pd‐Ni/C) were used for glycerol electrooxidation and commercial Pt/CHSA was used as cathode electrocatalyst. The anolyte is glycerol mixed with KOH electrolyte. The atmospheric air and calcium hypochlorite mixture are used as oxidant in cathode and catholyte, respectively. Acetylene black carbon is used as electrocatalyst support with low metal loading of 20 wt% Pd and Ni at their different weight ratios (Pd/Ni) of 16:4, 10:10, and 4:16 to synthesize bimetallic Pd‐Ni/C anode electrocatalysts. The crystal structure of the synthesized electrocatalyst was determined by X‐ray diffraction (XRD) analysis. The surface morphology and surface concentration of synthesized electrocatalyst were determined by scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX), respectively. The particle size of synthesized electrocatalyst was determined by transmission electron microscopy (TEM) analysis. The electrochemical activity of Pd‐Ni/C was investigated by cyclic voltammetry analysis. The electrocatalyst Pd‐Ni (10:10)/C gives higher electrocatalytic activity for glycerol electrooxidation compared to other ratios of electrocatalyst. A single air breathing μFC is investigated using various key parameters where air alone as oxidant gives open circuit voltage (OCV) of 0.42 V and maximum power density of 1.27 mW/cm2. While using calcium hypochlorite and air as mixed oxidant, the OCV was increased to 0.72 V and maximum power density increased to 3.43 mW/cm2, which are 1.71 and 2.7 times, respectively, more than that of air as oxidant only. [ABSTRACT FROM AUTHOR]

The present work focuses on the optimization of operating parameters using Box Behnken design (BBD) in RSM to obtain maximum power density from a glycerol based air-breathing T-shaped MFC. The major parameters influencing the experiment for enhancing the cell performance in MFC are glycerol/fuel concentration, anode electrolyte/KOH concentration, anode electrocatalyst loading and cathode electrolyte/KOH concentration. The ambient oxygen is used as the oxidant. The acetylene black carbon (C AB) supported laboratory synthesized electrocatalyst Pd–Pt (16:4)/C AB is used as anode electrocatalyst and commercial Pt (40 wt%)/C HSA as the cathode electrocatalyst. The quadratic model predicts the appropriate operating conditions to achieve highest power density from the laboratory designed T-shaped MFC. The p-value of less than 0.0001 and F-value of greater than 1 i.e., 26.32 indicate that the model is significant. The optimum conditions predicted by the RSM model were glycerol concentration of 1.07 M, anode electrolyte concentration of 1.62 M anode electrocatalyst loading of 1.12 mg/cm2 and cathode electrolyte concentration of 0.69 M. The negligible deviation of only 1.07% between actual/experimental power density (2.76 mW/cm2) and predicted power density (2.79 mW/cm2) was recorded. This model reasonably predicts the optimum conditions using Pd–Pt (16:4)/C AB electrocatalyst to obtain maximum power density from glycerol based MFC. Image 1 • Synthesized Pd–Pt (16:4)/C AB anode electrocatalyst is used for glycerol electrooxidation. • Air breathing F-shaped microfluidic fuel device used for single cell study. • Operating parameters for air breathing T-shaped MFC were optimized by RSM. • Maximum power density predicted by model (2.79 mW/cm2) is very close to experimental. [ABSTRACT FROM AUTHOR]

Pt-Ru and Pt–Re and Pt-Ru-Re nanoparticles supported on functionalized multi-walled carbon nanotubes (f-MWCNT) were synthesized via modified polyol reduction method and tested thoroughly in a half cell and single direct ethanol fuel cell for ethanol electrooxidation in acidic medium. The MWCNTs were functionalized in a mixture of HNO 3 /H 2 SO 4 solution for depositing a more active metal alloy nanoparticle on support material. The alloy formation of bi-metallic and tri-metallic electrocatalysts were examined by XRD analysis and more clearly explained by FE-SEM element mapping. The TEM analyses reveal that electrocatalysts nanoparticles are well dispersed on f-MWCNT, with spherical shapes and nano sizes range of 1.5–4 nm. The electrochemical analyses by cyclic voltammetry and chronoamperometry measurements reveal that tri-metallic electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT exhibits the highest electrocatalytic activity and stability towards ethanol electrooxidation among all the synthesized electrocatalysts. The same electrocatalyst as anode in single DEFC results in excellent performance in comparison to all other synthesized electrocatalysts, with a maximum power density of 9.52 mW/cm2 at a cell temperature of 30 °C. The bi-metallic Pt-Ru (1:1)/f-MWCNT and Pt–Re (1:1)/f-MWCNT produced power density of 7.48 mW/cm2 and 4.74 mW/cm2 at room temperature of 30 °C. The power density of DEFC enhanced 2.44 times, when cell operating temperature was increased from 30 °C to 80 °C using anode electrocatalyst Pt-Ru-Re (1:1:0.5)/f-MWCNT and keeping other parameters constant. The best result obtained in half cell and single DEFC using Pt-Ru-Re (1:1:0.5)/f-MWCNT electrocatalyst may be attributed to the synergistic effect of Pt, Ru and Re combined with bi-functional and ligand effects. • Functionalized f-MWCNTs proved to be excellent support material of electrocatalyst. • Re addition to Pt-Ru electrocatalyst enhanced ethanol electrooxidation kinetics. • Pt-Ru-Re (1:1:0.5)/f-MWCNT exhibits highest electrocatalytic activity for ethanol fuel. • Very low loading of anode Pt-Ru-Re (1:1:0.5)/f-MWCNT was used in DEFC study. [ABSTRACT FROM AUTHOR]

Abstract: A polyvinyl alcohol (PVA) based alkaline membrane was developed in the laboratory for use in direct methanol fuel cell (DMFC). This study investigates the performance of the alkaline PVA membrane, crosslinked by a physical crosslinking method. The membrane was characterized using water uptake, KOH uptake, ion exchange capacity, and ionic conductivity methods. The anode and cathode electrocatalysts were Pt‐Ru (30:15 % by wt)/carbon black (C) and Pt (40 % by wt)/high surface area carbon (CHSA), respectively. A similar electrocatalyst loading in the order of 1 mg/cm2 was used at the anode and cathode. The cell voltage and current density data were recorded for different concentrations of fuel (methanol) and electrolyte (KOH). The optimum conditions for the fuel cell were 2 M methanol mixed in 3 M KOH solution at a flow rate of 2 mL/min with a cathode feed of humidified oxygen at a flow rate of 100 mL/min. The DMFC was operated at 30 °C, irrespective of other operating conditions. The maximum open circuit voltage of 0.6 V, current density of 7.71 mA/cm2 at a cell voltage of 0.23 V, and maximum power density of 1.79 mW/cm2 were obtained at the optimum cell condition. The KOH‐doped PVA solid electrolyte was successfully tested in a direct methanol fuel cell, which results in excellent power density. Single cell test results prove that the physically crosslinked KOH‐doped PVA electrolyte could be used as a suitable solid electrolyte in a fuel cell. [ABSTRACT FROM AUTHOR]

A microfluidic fuel cell (MFC) is constructed at laboratory for NaBH 4 electrooxidation using varying operating conditions. The temperatures of anode and cathode were varied from 40 °C to 70 °C, and the pressure was maintained at 1 bar. The anode and cathode electrocatalyst used was Pt (40 wt. %)/High Surface Area Carbon (CHSA) with loading in the range of 0.5 mg/cm 2 to 2 mg/cm 2 . The oxidant at cathode was atmospheric oxygen (21 mol % O 2 ). The commercial gas diffusion layer (GDL) was used as substrate at anode and air breathing cathode side. The cell voltage and current density were measured for different fuel (NaBH 4 ) concentration, electrolyte (KOH) concentration, temperature and electrocatalyst loading at anode and cathode, respectively. The maximum open circuit voltage (OCV) of 1.079 V and power density of 24.09 mW/cm 2 at a current density of 54.97 mA/cm 2 were obtained for anode (Pt/C HSA ) and cathode (Pt/C HSA ) loading of 1 mg/cm 2 using 0.1 M NaBH 4 as fuel mixed with 1 M KOH as electrolyte at a temperature of 70 °C. Whereas the maximum power density of 8.47 mW/cm 2 at a current density of 34.04 mA/cm 2 was obtained at the temperature of 40 °C. Although similar cell conditions were used, the cell performance in terms of power density is significantly enhanced (about 65%) due to increase in temperature from 40 °C to 70 °C. These results were validated using cyclic voltammetry at single electrodes under similar conditions to those of the single microfluidic fuel cell. [ABSTRACT FROM AUTHOR]