Ahmad M. Mohammad Alakraa

Abstract The current study addresses, for the first time, the enhanced direct electro-oxidation of formic acid (FA) at platinum-nanoparticles modified glassy carbon (nano-Pt/GC) electrode in the presence of methanol (MeOH) as a blending fuel. This enhancement is probed by: (i) the increase of the direct oxidation current of FA to CO2 ((Formula presented.), dehydrogenation pathway), (ii) suppressing the dehydration pathway ((Formula presented.), producing the poisoning intermediate CO) and (iii) a favorable negative shift of the onset potential of (Formula presented.) with increasing the mole fraction of MeOH in the blend. Furthermore, the charge of the direct FA oxidation in 0.3 M FA + 0.3 M MeOH blend is by 14 and 21times higher than that observed for 0.3 M FA and 0.3 M MeOH, respectively. MeOH is believed to adsorb at the Pt surface sites and thus disfavor the "non-faradaic" dissociation of FA (which produces the poisoning CO intermediate), i.e., MeOH induces a high CO tolerance of the Pt catalyst. The enhanced oxidation activity indicates that FA/MeOH blend is a promising fuel system. © 2015 Elsevier B.V. All rights reserved.

In this investigation, the catalytic activity of palladium nanoparticles (PdNPs)-modified glassy carbon (GC) (simply noted as PdNPs/GC) electrodes towards the formic acid electro-oxidation (FAO) was investigated. The deposition of PdNPs on the GC substrate was carried out by a potentiostatic technique at different potentials and the corresponding influence on the particles size and crystal structure of PdNPs as well as the catalytic activity towards FAO was studied. Scanning electron microscopy (SEM) demonstrated the deposition of PdNPs in spherical shapes and the average particle size of PdNPs deposited at a potential of 0 V vs. Ag/AgCl/KCl(sat.) was the smallest (ca. 8 nm) in comparison to other cases, where the deposition proceeded at higher potentials. The electrochemical measurements agreed consistently with this, where the highest surface area of PdNPs was calculated similarly for the deposition carried out at 0 V vs. Ag/AgCl/KCl(sat.). Interestingly, the X-ray diffraction (XRD) analysis revealed a similar dependency of the PdNPs crystal structure on their particle size and distribution. The deposition of PdNPs at 0 V vs. Ag/AgCl/KCl(sat.) seemed exhibiting the best crystallinity. From the electrocatalytic point of view, the activity of the PdNPs/GC electrode towards FAO decreased with the deposition potential of PdNPs, which influenced consequently the particle size, shape, and/or crystallographic orientation of PdNPs. © Springer International Publishing Switzerland 2015.

This paper addresses a systematic study of the unexpected enhancement of some hydrocarbon impurities towards formic acid oxidation (FAO) at Pt nanoparticles modified GC electrode, for the first time. That is, the oxidation current peak observed at ca. 0.25 V (assigned for the direct FAO to CO2, Ipd) increases in the presence of a minute amount (∼ppm range) of Acetonitrile > Acrylonitrile > Acetamide > Pyridine ∼ vinyl acetate > Pyrrole > Methyl Acrylate > toluene with a concurrent decrease of the second oxidation peak current (assigned for the indirect oxidation of FA, Ipind) observed at ca. 0.65 V. Moreover, the onset potential of FAO is favored by shifted towards the negative potentials together with a noticeable increase of the stability of the current transients measured during FAO in the presence of impurities. The enhanced activity is believed to originate from interrupting the contiguity of Pt sites by the pre-adsorption of the respective impurity at nano-Pt surface thus impedes/weakens the adsorption of the poisoning CO. © 2015 Elsevier Ltd. All rights reserved.

The current study addresses the enhanced electroctrocatalytic activity of a nanoparticle-based ternary catalyst composed of Pt (nano-Pt), manganese oxide (nano-MnOx), and cobalt oxide (nano-CoOx) (all were assembled on a glassy carbon (GC) substrate) towards the direct methanol electro-oxidation reaction (MOR) in an alkaline medium. The electrocatalytic activity of the modified electrodes towards MOR depends on the loading level of nano-Pt, nano-MnOx, and nano-CoOx onto the GC electrode as well as the order of deposition of each component. Interestingly, the CoOx/MnOx/Pt/GC electrode (with nano-Pt firstly deposited onto the GC surface followed by nano-MnOx then nano-CoOx) shows the highest catalytic activity and stability towards MOR for a prolonged time of continuous electrolysis. This is revealed from the large increase (seven times) in the peak current of MOR at this electrode compared with that obtained at Pt/GC electrode. The influence of operating pH on the catalytic activity of the proposed catalyst is investigated. Several techniques including cyclic voltammetry, field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy and X-ray diffraction are used to address the catalytic activity of the catalyst and to reveal its surface morphology and composition. © 2015 Elsevier Ltd. All rights reserved.

The current investigation presents a novel catalyst for formic acid electro-oxidation (FAO); the essential anodic reaction in direct formic acid fuel cells (DFAFCs). The catalyst is developed by a sequential electrodeposition method for Pt (PtNPs), Au (AuNPs) and nickel oxide (nano-NiOx) nanoparticles onto the surface of a glassy carbon (GC) electrode. The objective of this modification was solely dedicated to the improvement of the electrode's catalytic activity by overcoming the CO poisoning, which is usually responsible for the deterioration of the catalytic performance of DFAFCs. The deposition sequence of the catalyst ingredients (PtNPs, AuNPs, and nano-NiOx) was adjusted to optimize the electrocatalytic activity and stability of the catalyst towards FAO. Interestingly, the highest catalytic activity and stability towards FAO was obtained at the NiOx/Au/Pt/GC electrode in which PtNPs were directly deposited onto the GC electrode followed by AuNPs then nano-NiOx. The discussion is oriented to adopt the role of the ternary catalyst ingredients in the catalytic enhancement. © 2014 Hydrogen Energy Publications, LLC.

Minute amount (∼1 ppm) of acrylonitrile (AcN), a possible contaminant, shows an unexpected enhancement for the direct electro-oxidation of formic acid (FAO) at Pt nanoparticles modified GC (nano-Pt/GC) electrodes. This is reflected by a remarkable increase of the current intensity of the direct oxidation peak (Ip d, at ca. 0.3 V) in the presence of AcN, concurrently with a significant decrease of the second (indirect) oxidation current (I p ind, at ca. 0.7 V), compared to that observed in the absence of AcN (i.e., at the unpoisoned Pt electrode). The extent of enhancement depends on the surface coverage (θ) of AcN at the surface of Pt nanoparticles. AcN is thought to favor the direct FAO by disturbing the contiguity of the Pt sites, which is necessary for CO adsorption. Furthermore, XPS measurements revealed a change in the electronic structure of Pt in presence of AcN, which has a favorable positive impact on the charge transfer during the direct FAO. © 2014 Elsevier B.V. All rights reserved.

Hydroxyapatite nanorods (nHAp) and nano-hydroxyapatite chitosan composites (nHApCs) were proposed for the removal of Cd2+ ions in water treatment. The high resolution transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction spectrophotometer, Fourier transform infrared spectrophotometer and Zeta potential measurements were all employed to reveal the morphology, composition, crystal structure, functionality and stability of the prepared sorbents (nHAp and nHApCs). The potential of these synthesized sorbents to remove Cd2+ ions from aqueous solutions was investigated in batch experiments, where several parameters such as the sorbate/sorbent's contact time, initial Cd2+ ions concentration, pH and sorbent dosage were investigated. The equilibrium concentration of Cd2+ ions was identified by the atomic absorption spectrophotometry. The Cd2+ uptake was quantitatively evaluated using the Pseudo second order kinetic equation, Freundlich and Langmuir models. It is remarkable that with these sorbents (nHAp, nHApCs), up to 92% of Cd2+ could be removed "100ppm initial cadmium concentration in 200mL, 0.4g nHAp and pH=5.6″. The sorption capacity of nHAp and nHApCs to Cd2+ was 92 and 122mg/g respectively, which appears excellent when compared to other previously reported materials. This capacity could be enhanced by increasing initial Cd2+ concentration and the nHAp/Cd2+ mass ratio. Furthermore, the sorbents' regeneration was addressed and found promising. © 2013 Taiwan Institute of Chemical Engineers.

In this investigation, a nanoparticle-based binary catalyst composed of nickel oxide (nano-NiOx) and manganese oxide (nano-MnOx), both were assembled on a platinum substrate, was developed for the direct methanol electro-oxidation (MO) in an alkaline medium. The morphological investigation was performed using field-emission SEM and revealed the electrodeposition of MnOx in a nanorod structure and NiOx in round-shaped nanospheres. The electrocatalytic activity of the modified electrodes towards MO depended critically on the order of deposition of the two oxides. The optimum electrocatalytic activity was obtained at the MnOx/NiOx/Pt electrode (in which nano-NiOx was directly electrodeposited onto the Pt surface followed by nano-MnOx) with a total surface coverage of ca. 86%. Both nano-NiOx and nano-MnOx are believed to act as catalytic mediators facilitating the adsorption of methanol and the charge transfer during MO. © 2014 The Authors.

The modification of a glassy carbon (GC) electrode with platinum (PtNPs) and gold (AuNPs) nanoparticles was intended to fabricate efficient anodes for the formic acid electro-oxidation (FAO). A suitable deposition sequence of PtNPs and AuNPs was adjusted to enhance the electrocatalytic activity of the electrode in such a way suppressing the CO poisoning that usually deteriorates the electrode's catalytic activity during FAO. Morphologically, PtNPs were deposited in a spherical shape (with an average diameter of 37 nm), while AuNPs appeared in granules (with an average diameter of 43 nm) both were uniformly dispersed on the GC surface. The highest electrocatalytic activity was obtained at the Au-Pt/GC electrode (for which PtNPs was deposited first on the GC electrode then AuNPs). Interestingly, AuNPs could successfully interrupt the contiguity of Pt surface sites in a way preventing the CO poisoning. Moreover, the Au-Pt/GC electrode exhibited excellent tolerance against poisoning influenced by chloride ions, which usually contaminate the fuel cell and have a similar impact as CO. The relationship between the degree of electrode's tolerance against the catalytic deactivation and the chloride ion concentration was addressed. © 2014 The Authors. Published by ESG.

The global interest to realize and commercialize the direct formic acid fuel cells has motivated the development of efficient and stable anodes for the formic acid (FA) electro-oxidation (FAO). In this investigation, a ternary catalyst composed of Pt nanoparticles (PtNPs), Au nanoparticles (AuNPs) and nickel oxide nanoparticles (nano-NiOx), all were sequentially electrodeposited onto the surface of a glassy carbon (GC) electrode, was recommended for this reaction. The surface morphology investigation revealed the deposition of grain-shaped PtNPs (25 nm average particle size), and flower-shaped nanospheres (less than 60 nm average particle size) of AuNPs and nano-NiOx. Interestingly, the ternary modified NiO x-Au-Pt/GC electrode has shown an outstanding electrocatalytic activity towards the direct FAO, concurrently with a complete suppression for the indirect route. It further exhibited excellent stability that extended for 7 h of continuous electrolysis. While PtNPs furnished a suitable base for FA adsorption, AuNPs played a significant role to interrupt the contiguity of the Pt surface sites, which is necessary for CO poisoning. On the other hand, nano-NiOx acted as a catalytic mediator facilitating the charge transfer of FAO and the oxidative removal of CO at a lower potential. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Here we demonstrate a remarkable enhancement of the direct formic acid electro-oxidation (FAO) to CO2 (dehydrogenation pathway, Ip d) at Pt nanoparticle-modified GC (nano-Pt/GC) electrodes, in the presence of minute amount (∼ppm) of vinyl acetate (VA), while suppressing the dehydration pathway (producing the poisoning intermediate CO, Ip ind). An excellent electrocatalytic activity of the nano-Pt/GC catalyst for FAO was found in the presence of VA (a possible contaminant) as revealed by comparing the intensity of the corresponding two oxidation peaks Ip d and Ip ind observed respectively at 0.25 and 0.75 V vs Ag/AgCl/KCl(sat.). The degree of enhancement of Ip d depends on the surface coverage (θ) of VA at Pt nanoparticles. VA is believed to adsorb and consequently interrupt the surface contiguity of the Pt active sites favorable for CO poisoning. XPS measurements revealed a change in the electronic properties of Pt in the presence of VA in such a way that favors the charge transfer during the FAO and/or impedes/weakens the adsorption of the poisoning CO. Interestingly, VA (in ppm concentration) improves the electrode's stability during FAO and also its catalytic tolerance against poisoning with chloride ions. Several indices were developed to measure the catalytic activity of the electrode in the absence and presence of VA, and several techniques as FE-SEM, XRD, EDX, and XPS were employed in the revelation of the electrode's morphology, crystal structure, composition, and binding energy. © 2014 American Chemical Society.

This study addresses the electrocatalytic oxidation of formic acid (FA) at binary catalysts composed of Pt nanoparticles (nano-Pt) and nickel oxide nanoparticles (nano-NiOx) electrodeposited onto glassy carbon (GC) electrodes. Pt electrode shows two oxidation peaks at ca. 0.25 and 0.65 V vs. Ag/AgCl/KCl (sat.) corresponding to the direct (Ipd, favorable) and indirect (Ipind, unfavorable) oxidation pathways of FA, respectively. Nano-Pt/GC electrode shows a significantly higher catalytic activity toward FA oxidation than the bulk Pt electrode. Interestingly, further modification of the nano-Pt/GC electrode with nano-NiOx leads to a superb enhancement of Ipd with a concurrent suppression of Ipind. The catalytic activity of the various modified GC electrodes is probed by the ratio of Ipd/Ipind. This ratio increases from 0.2 at bulk Pt to 1.4 at nano-Pt/GC (i.e., ca. 7 times higher), and jumps up to more than 20 at the binary nano-NiOx/nano-Pt modified GC electrode, reflecting the superiority of the latter electrode toward FA oxidation to CO2. While nano-Pt furnishes a suitable base for FA adsorption, nano-NiOx acts as a catalytic mediator which facilitates the charge transfer during the direct oxidation of FA. The influence of the deposition sequence and the loading level of both species (i.e., Pt and NiO x) on the catalytic activity of the binary catalyst are investigated. © 2013 Elsevier Ltd. All rights reserved.

This study addresses the enhancement of the oxygen evolution reaction (OER) on glassy carbon, Au, and Pt electrodes modified with binary catalysts composed of nickel oxide nanoparticles (nano-NiOx) and cobalt oxide nanoparticles (nano-CoOx). Binary NiOx/CoO x-modified electrodes (with NiOx initially deposited) show a high catalytic activity and a marked stability which far exceeds that obtained at the individual oxide-modified electrodes. This enhancement is demonstrated by a marked negative shift (more than ca. 600 mV) in the onset potential of the OER compared to that obtained at the unmodified electrodes. The modified electrodes show a significantly higher long-term stability, over a period of 5 h of continuous electrolysis, without any significant loss of activity towards the OER in alkaline medium. The influence of the solution pH, the loading level, and sequence of deposition of each oxide on the electrocatalytic activity of the modified electrodes is addressed with an aim to maximize the catalytic activity of the modified electrodes towards the OER. SEM imaging is used to disclose the size and morphology of the fabricated nano-NiOx and nano-CoOx binary catalysts at the electrode surface. © 2012 Springer-Verlag Berlin Heidelberg.

A colloidal solution of citrate-stabilized gold nanoparticles (AuNPs) with an average size of ca. 2.6 nm has been prepared, characterized and further implemented in electro-sensing applications. This colloidal solution of AuNPs has been prepared via the reduction of NaAuCl4 with sodium tetrahydroborate (NaBH4) using trisodium citrate as a stabilizer. The optical properties of this solution have been studied with UV-Vis spectroscopy. Next, these AuNPs have been immobilized onto a polycrystalline Au (poly-Au) electrode with the assistance of benzenedimethanethiol (BDMT), which served as a binder. Attention has been taken to ensure the formation of a compact impermeable layer of BDMT on poly-Au electrode, in order isolate the ploy-Au surface from participating in the upcoming applications. Interestingly, the AuNPs-modified Au electrode has shown a better sensing capability for ascorbic acid than that of the bare poly-Au, which opens opportunities for future designing of nanoparticles-based biological sensors. © 2013 by ESG.

The modification of a glassy carbon (GC) electrode with platinum (PtNPs) and gold (AuNPs) nanoparticles is targeted to fabricate efficient anodes for the electrooxidation of formic acid (FA). A proper adjustment of the deposition sequence of PtNPs and AuNPs could eventually enhance the electrocatalytic activity of the electrode in such a way that suppresses the CO poisoning effect during FA oxidation. The highest catalytic activity is obtained at the Au/Pt/GC electrode (with PtNPs firstly deposited on the GC electrode followed by AuNPs). This superb enhancement is quantified by comparing the relative ratio of the direct vs. the indirect oxidation peaks at 0.3 and 0.65 V, respectively, at each electrode. The fundamental role of AuNPs (in Au/Pt/GC electrode) imparts immunity to the underlying PtNPs against CO poisoning by interrupting the contiguity of the Pt surface sites, thus, prevents the deterioration of the catalytic activity of the anode. © 2012 by ESG.

The analysis of a ternary mixture containing ozone (O 3), sodium hypochlorite (NaClO), and hydrogen peroxide (H 2O 2), in their coexistence was simultaneously performed using a potentiometric method. In this method, the change in the open circuit potential of a Pt indicator electrode dipped in a potential buffer containing I -/I 3 - upon the addition of the ternary mixture is measured. The analysis was based on the different reaction kinetics of the three oxidants with I -. The kinetics of the reaction of O 3 and I - is about three orders of magnitude faster than that of sodium hypochlorite, and the reaction of hydrogen peroxide and I - is negligible compared with those of O 3 or hypochlorite ion and I - unless a molybdate catalyst is added. Several factors, including the iodide concentration, pH, and the molybdate concentration were investigated to optimize the analysis and achieve a reasonable separation among the reactions of the three oxidants and I -. A theoretical model was developed to compare with the experimental results and a reasonable correlation was obtained. © 2012 Copyright Taylor and Francis Group, LLC.

The current study addresses the superior electrocatalytic activity of nickel oxide nanoparticles (nano-NiO x) modified GC, Au and Pt electrodes towards the OER. The electrodeposition of nickel oxide nanoparticles (with an average particle size of 80 nm) are believed to enhance the OER reaction. NiOOH phase, as shown from XRD data, participates in the OER mechanism in such a way to facilitate the charge transfer during various steps in the reaction mechanism through a reversible transformation of NiOOH to NiO 2. Optimizing the loading level and the operating pH of the proposed catalyst has been carried out. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The electrocatalysis of oxygen evolution reaction (OER) at cobalt oxide nanoparticles (nano-CoO x) modified GC, Au and Pt electrodes has been examined using cyclic voltammetry. The OER is significantly enhanced upon modification of the electrodes with nano-CoO x, as demonstrated by a negative shift in the polarization curves at the nano-CoO x modified electrodes compared to that obtained at the unmodified ones. Scanning electron microscopy (SEM) revealed the electrodeposition of nanometer-size CoO x (average particle size of 200 nm) onto GC electrode. Optimization of the operating experimental conditions (i.e., solution pH and loading level of nano-CoO x) has been achieved to maximize the electrocatalytic activity of nano-CoO x modified electrodes. It has been found that the electrocatalytic activity of the nano-CoO x modified electrodes towards the OER is pH and loading level dependent, while it is substrate independent. The low cost as well as the marked stability of the thus-modified electrodes make them promising candidates in industrial water electrolysis process. © 2012 by ESG.

This study addresses the electrocatalytic oxidation of formic acid (FA) at nickel oxide nanoparticles (nano-NiOx) modified Pt, Au, GC anodes. FA oxidation proceeds at the unmodified Pt electrode with the appearance of two oxidation peaks at 0.25 and 0.65 V corresponding to the direct oxidation of FA to CO 2 and the oxidation of the poisoning intermediate, CO, to CO 2 with a current ratio of the two peaks less than 0.2. Interestingly, this ratio jumps up to more than 50, upon modifying Pt with nano-NiOx. This highlights the essential role of NiOx in enhancing the direct oxidation of FA (at 0.25 V) at Pt substrate. On the other hand, unmodified GC and Au anodes as well as those modified with nano-NiOx exhibit no catalytic response toward FA oxidation. This highlights the essential role of the underlying substrate and depicts also that nano-NiOx behaves as a catalytic mediator which facilitates the charge transfer during the oxidation of FA at Pt anode. Optimization of the surface coverage of nano-NiOx at Pt is achieved, aiming at maximizing the rate of the direct oxidation pathway of FA while suppressing the indirect oxidation route producing the poisoning CO. Moreover, nano-NiOx/Pt anode maintains its high catalytic activity for a prolonged time of continuous oxidation of FA. © 2012 The Electrochemical Society.

This chapter describes our findings over the last few years, concerning the use of electrodeposition as a facile technique for the fabrication of several thin films of noble metals, nanostructures and nanorods onto various substrates. This includes three tasks. Firstly: the electrodeposition of metallic Ni or Cu thin films on reticulated vitreous carbon (RVC), and Pd or black Ni onto copper screens for use as electro-catalytically active cathodes for the hydrogen evolution reaction (HER). Moreover, the effects of some hydrodynamic and solution parameters concerning the performance of the electrodeposition process of heavy metal ions (e.g., lead ions) from flowing wastewater are briefly discussed. Secondly: the fabrication (via electrodeposition) of metallic (e.g., Au) and metal oxide (e.g., manganese oxide) nanostructures for application in fuel cell catalysis including the oxygen reduction and evolution reactions in addition to formic acid oxidation. Details of the morphological and electrochemical characterizations of the thus-electrodeposited nanostructures are outlined. This includes scanning electron microscope imaging (SEM), electron back scatter diffraction (EBSD) and X-ray diffraction (XRD) patterns. Thirdly: the fabrication of one-dimensional nanostructures, i.e., nanowires, for vital electronic, chemical, biological, and medical applications. Several methodologies are outlined for this sake; however, the electrodeposition in templates seems more interesting in terms of cost and potential for high volume production. The recent work combining the electrodeposition and the template growth approach for nanofabrication is introduced. Special emphasis is dedicated to assembling metal-semiconductor nanowire contacts in which the contact interface is formed along the cross-section of the wire. © 2012 Nova Science Publishers, Inc. All rights reserved.

The electrocatalysis of oxygen evolution reaction (OER) at cobalt oxide nanoparticles (nano-CoO x) modified GC, Au and Pt electrodes has been examined using cyclic voltammetry. The OER is significantly enhanced upon modification of the electrodes with nano-CoO x, as demonstrated by a negative shift in the polarization curves at the nano-CoO x modified electrodes compared to that obtained at the unmodified ones. Scanning electron microscopy (SEM) revealed the electrodeposition of nanometer-size CoO x (average particle size of 200 nm) onto GC electrode. Optimization of the operating experimental conditions (i.e., solution pH and loading level of nano-CoO x) has been achieved to maximize the electrocatalytic activity of nano-CoO x modified electrodes. It has been found that the electrocatalytic activity of the nano-CoO x modified electrodes towards the OER is pH and loading level dependent, while it is substrate independent. The low cost as well as the marked stability of the thus-modified electrodes make them promising candidates in industrial water electrolysis process. © 2012 by ESG.

This study addresses the electrocatalytic oxidation of formic acid (FA) at nickel oxide nanoparticles (nano-NiOx) modified Pt, Au, GC anodes. FA oxidation proceeds at the unmodified Pt electrode with the appearance of two oxidation peaks at 0.25 and 0.65 V corresponding to the direct oxidation of FA to CO 2 and the oxidation of the poisoning intermediate, CO, to CO 2 with a current ratio of the two peaks less than 0.2. Interestingly, this ratio jumps up to more than 50, upon modifying Pt with nano-NiOx. This highlights the essential role of NiOx in enhancing the direct oxidation of FA (at 0.25 V) at Pt substrate. On the other hand, unmodified GC and Au anodes as well as those modified with nano-NiOx exhibit no catalytic response toward FA oxidation. This highlights the essential role of the underlying substrate and depicts also that nano-NiOx behaves as a catalytic mediator which facilitates the charge transfer during the oxidation of FA at Pt anode. Optimization of the surface coverage of nano-NiOx at Pt is achieved, aiming at maximizing the rate of the direct oxidation pathway of FA while suppressing the indirect oxidation route producing the poisoning CO. Moreover, nano-NiOx/Pt anode maintains its high catalytic activity for a prolonged time of continuous oxidation of FA. © 2012 The Electrochemical Society.

The effect of the operating relative humidity (RH) values on the temperature and current distributions within a 5-5 segmented H 2/air polymer electrolyte membrane fuel cell was studied. Different relative humidity values were applied ranging from 0 to 100%. All the measurements were done at a constant potential mode rather than a constant current mode. While the temperature distributions in front of the 5 subcells at different RH values were measured using thermocouples inserted at the back of the graphite current collectors, and the current distributions within these 5 subcells were measured using 5 potentiostats that have been used as zero resistance ammeters. The results show significant temperature gradients at the different loads as a function of the operating RH values. In addition, the fraction of current (α) passed through every subcell revealed interesting behaviors at the corresponding RH values. ©The Electrochemical Society.