Hydrogen Evolution Characteristics Research Articles

Design and performance analysis of a PV-assisted alkaline electrolysis for hydrogen production: An experimental and theoretical study

The PV assisted alkaline electrolysis cell was established for hydrogen generation. Lab-made AgNiCu modified nickel foam cathodes were used in this system. The characterization was achieved using field emission scanning electron microscopy, energy-dispersive X-ray and X-Ray diffraction analysis. The electrochemical performance was investigated via linear sweep voltammetry, cyclic voltammetry, Tafel polarization measurements and electrochemical impedance spectroscopy. The electrolysis potential and time depended efficiency was monitored. The structural theoretical analysis of the electrode surface and hydrogen evolution characteristics were also determined applying Density Functional Theory and Ab-initio Molecular Dynamics simulations which identified the role of Ag decoration and Cu incorporation on the surface against water and proton adsorptions. The modified cathode (AgNiCuF) improved the hydrogen production performance owing to lower hydrogen onset potential (−1.1 V) and charge transfer resistance (0.362 ohm at −1.5 V).

Two one-dimensional silver(I) coordination polymer modified electrodes for hydrogen evolution reaction and H2O2 recognition

Two new Ag(I) coordination polymers (CPs), namely: [Ag4(m-MOPhHIDC)2(BBM)2]n (1) {[Ag(BBM)](NO3)}n (2) (m-MOPhHIDC = m-methoxyanisaldehyde imidazole dicarboxylate, BBM = 2,2-(1,4-butanediyl)bis-1,3-benzimidazole), have been synthesized by solvothermal method and characterized. Structural analyses show that both complexes are one-dimensional chain coordination polymers, but the one-dimensional chains have different shapes, in which CP-1 is "V" shaped, and CP-2 is "wave-shaped". The electrochemical properties of composite electrodes CE-1 and CE-2 formed by mixing two coordination polymers with carbon paste electrodes were investigated respectively. Electrocatalytic hydrogen evolution characteristics of two composite electrodes were investigated by linear scanning voltammetry (LSV) in 0.5 M H2SO4 electrolyte, at 298 K the results show that when the current density reaches 10 mA cm−2, their overpotential positively shifted by 284 and 289 mV compared to CE (905 mV). And the Tafel slope of the CE-1 and CE-2 was 162 and 164 mV dec−1, respectively. The CE-1 exhibited superior electrocatalytic ability than CE-2, which may be attributed to the different coordination modes of central silver ions in the two CPs. In addition, the composite electrodes CE-1 and CE-2 also have a good identification effect on H2O2, and the detection limits of 36.7 and 6.2 μM in the linear range of 0.5-4000 μM were determined by chronoamperometry. Results show that the Ag(I) CPs can be used as effective dualfunctional electrocatalysts.

Improved electrocatalytic hydrogen evolution characteristics in Mn-doped MoS2 nanosheets grown under a non-equilibrium condition

Two-dimensional (2D) monolayer pristine MoS2 transition metal dichalcogenide (TMDC) is the most investigated material due to its potential applications as a non-precious electrocatalyst for the hydrogen evolution reaction (HER). However, the active edge sites created by sulfur non-stoichiometry and a defect-engineering by selective doping play a vital role in activating inert basal planes and enhancing the HER activity. Herein we report the synthesis of highly disordered Mn-doped 2D-MoS2 nanospheres by a simple hydrothermal route under a non-equilibrium growth condition. Excess sulfur content in the precursor and electron-rich atmosphere created by Mn-doping results in an increased domain-based defects in the lattice that enhances the number of exposed edge sites, and also exposing more catalytically active high-index planes. Thereby improving its physicochemical properties. The developed electrode shows a low overpotential of 186 mV at a current density of 10 mA/cm2 and a low Tafel slope of 79.9mV/dec in acidic electrolytes. In addition, Density Functional Theory based calculation shows that Mn-doping in non-stoichiometric MoS2 enhances the electronic properties and its role in facilitating hydrogen adsorption and desorption processes with free energy close to that of benchmark Pt is established.

Tuning the Layered Thickness of MoTe2 Thin Film for Dye‐Sensitized Solar Cells, UV and Visible Spectrum Photodetectors, and Hydrogen Evolution Reaction

Atomically thick van der Waals (VdW)‐bonded layered transition metal dichalcogenide (TMD) structures have influenced the investigation of novel phenomena for modern electronics and energy devices immensely. Herein, the fabrication of atomically thick tunable mollybednum ditelluride thin films on substrates through a chemical bath methodology is shown for the first time. The proposed methodology can be used to fine tune the atomic layer thickness of MoTe2 with highly modified surface characteristics, which is a greatly interesting feature for multifunctional nanodevice fabrication. Microscopic images confirm the atomic layer thickness‐tuned MoTe2. Furthermore, a photodetector assembled using few‐layer‐thick (S4) MoTe2 shows a high photoresponsivity of 3.21 A W−1 under ultraviolet light and an excellent detectivity of 5.4 × 1011 Jones, and a dye‐sensitized solar cell constructed using a photocathode made from S4 MoTe2 atomic layers shows a high power conversion efficiency of 8.44%, which is much greater than that of many other layered TMD structures. In addition, synthesized S4 MoTe2 atomic layers exhibit excellent hydrogen evolution characteristics in alkaline and acidic media. The resulting outcomes obviously establish the advantages of developed layered thick MoTe2 to produce the outstanding interface characteristics between the vdW‐bonded atomic layers to achieve outstanding energy and semiconductor devices.

Controllable preparation and electrocatalytic hydrogen evolution characteristics of Fe3S4 nanocrystals

In order to obtain better electrocatalytic hydrogen evolution performance, Fe3S4 with different morphologies was synthesized by controlling the reaction conditions. During that progress, the ferric oleate as an iron source, and the sulfur powder dissolved in oleylamine as a sulfur source. Fe3S4 with particle morphology proved to have the best electrochemical catalytic activity after adding 40% carbon black. In dehydrogenation, the overpotential was 234 mV and the Tafel slope was 213 mV/dec at a current density of 10 mA/cm2. Meanwhile, Fe3S4 with a particle morphology exhibited superior electrochemical stability. Therefore, the controllably fabricated Fe3S4 with a particle morphology is a promising electrocatalyst for dehydrogenation.

High excellent hydrogen evolution characteristics and novel mechanism of two-dimensional tetra-phase OsN2 and ReN2.

It is essential to find a kind of electrocatalyst for hydrogen evolution reduction (HER) comparable with a noble metal that has good conductivity and abundant active sites. Based on systematic searches by first-principles calculations, we discovered two-dimensional transition-metal nitrides, tetra-phase OsN2 and ReN2 monolayers, as potential HER electrocatalysts with superior thermodynamic and kinetic stability. They exhibited excellent catalytic activity due to the presence of multiple active sites with a density of 8 × 1015 site per cm2 and an overpotential close to 0. In addition, we also found that the synergistic effect of strain and coverage makes them have a good hydrogen evolution activity. The ΔGH of the OsN2 monolayer at 1% tensile strain under 3/4 hydrogen coverage is 0.02 eV, and that of ReN2 at 1/2 hydrogen coverage could decrease to 0.001 eV. Different from other common transition metal nitrides, we found that the active sites of OsN2 and ReN2 monolayers are both at nitrogen atoms, which could be further understood by the crystal orbital Hamiltonian population analysis between N and metal atoms. All these interesting findings not only provide new excellent candidates but also provide new insights into the mechanism of hydrogen evolution of nitrides.

Exponentially self-promoted hydrogen evolution by uni-source photo-thermal synergism in concentrating photocatalysis on co-catalyst-free P25 TiO2

The concentrating photocatalysis (CPC) to produce hydrogen can be considered as a promising strategy for cooperative utilization of light and heat of full-spectrum solar energy. However, its fundamental mechanism remains elusive and controversial. Here, the P25 TiO2 photocatalyst, which is optimized kinetically and thermodynamically under 36 × sun irradiation (1 × sun = 1 kW m−2), exhibits ultrahigh co-catalyst-free H2 evolution rate (235.8 μmol h−1), which is 1212 times of that in the conventional photocatalysis (PC) under 1 × sun irradiation as the benchmark. Moreover, hydrogen evolution has been identified to be exponentially correlated to reaction time (throughout the growing and stable temperature stages) and irradiance under Xe lamp and sunlight, respectively. These attractively superlinear characteristics of hydrogen evolution can be attributed to the uni-source photo-thermal synergism of accelerated carrier transfer rate by the high-density heat flux and broadened carrier transfer channel by the high-density photon flux. This work highlights the novel reaction characteristics and mechanisms for enhanced hydrogen evolution in CPC, thus provides new guidance to the performance improvement for conventional PC.

An Influence Study of Hydrogen Evolution Characteristics on the Negative Strap Corrosion of Lead Acid Battery

Negative strap corrosion is an important reason for the failure of valve regulated lead acid battery. This paper selected the Pb-Sb alloy material and Pb-Sn alloy material, made an investigation on the negative corrosion resistance and hydrogen evolution of these two alloy materials by scanning electron microscope analy- sis, metallographic analysis, chemical study and linear sweep voltammetry, and discussed the influence of lead alloy hydrogen evolution on the negative strap corrosion. The results showed that the hydrogen evolution reac- tion rates of the alloys had an impact on the corrosion areas with the maximum thickness of the alloys and the depth of corrosion layers. Greater hydrogen evolution reaction rate can lead to shorter distance between the cor- rosion area with the maximum thickness and the liquid level; whereas the greater corrosion layer thickness can bring aggravated risk of negative strap corrosion failure.

Hydrogen evolution of Cu precipitation 780 MPa grade steel HAZ with consideration of its cold cracking susceptibility

The Cu precipitation 780 MPa grade steel has higher resistance to cold cracking than the conventional steels. To study this, we have investigated the hydrogen evolution characteristics of the Cu steel heat-affected zone (HAZ) by the thermal desorption spectroscopy method and compared with those of conventional 780 MPa steel HAZ. The thermal cycle tests were conducted to obtain the HAZ microstructures, and the peak temperatures were selected from 500 to 1400 °C at intervals of 100 °C. Hydrogen was then charged, and the hydrogen evolution curves were measured at a heating rate of 100 °C/h. The results show that the amounts of hydrogen released from the specimens whose peak temperatures of the thermal cycle tests were 1000 °C or higher are lower, while the results of the conventional steels have the opposite tendency. We numerically calculated the hydrogen evolution curves to determine physical constants, and using these constants, we also calculated the hydrogen concentration profiles of the y-groove weld cracking test and found that the hydrogen concentration of the Cu steel HAZ near the fusion line tends to become lower than those of the conventional steel HAZ. This phenomenon is considered one of the reasons for the higher cold cracking resistance of the Cu steel.

Hydrogen production from hydrolysis of ammonia borane with limited water supply

Effect of limited water supply to hydrolysis of ammonia borane for hydrogen evolution is studied over the cases in which the initial molar ratio of water to ammonia borane (H2O/AB) is set at 1.28, 2.57 and 4.50. The conversion efficiency of ammonia borane to hydrogen is estimated from the accumulated volume of produced hydrogen gas and the quantitative analysis of hydrolysate by solid-state 11B NMR. Characteristics of hydrogen evolution are significantly influenced by both water dosage and injection rate of water. In the case that water is a limiting agent, namely, H2O/AB = 1.28, less hydrogen is produced than that predicted stoichiometrically. In contrast, conversion efficiency of ammonia borane reaches nearly 100% for the case with H2O/AB = 4.50. Injection rate of water to ammonia borane also affect profoundly the produced volume and production rate of hydrogen, if water is used as a limiting agent in the hydrolysis of ammonia borane. Nonetheless, boric acid and metaboric acid are found to be the dominant products in the hydrolysate from XRD, FT-IR and solid-state 11B NMR analysis. The hydrogen storage capacity using limited water supply in this work could reach as high as about 5.33 wt%, based on combined mass of reactants and catalyst.

Hydrogen-evolution characteristics of Ni–Mo-coated, radial junction, n+p-silicon microwire array photocathodes

The photocathodic H2-evolution performance of Ni–Mo-coated radial n+p junction Si microwire (Si MW) arrays has been evaluated on the basis of thermodynamic energy-conversion efficiency as well as solar cell figures of merit. The Ni–Mo-coated n+p-Si MW electrodes yielded open-circuit photovoltages (Voc) of 0.46 V, short-circuit photocurrent densities (Jsc) of 9.1 mA cm−2, and thermodynamically based energy-conversion efficiencies (η) of 1.9% under simulated 1 Sun illumination. Under nominally the same conditions, the efficiency of the Ni–Mo-coated system was comparable to that of Pt-coated n+p-Si MW array photocathodes (Voc = 0.44 V, Jsc = 13.2 mA cm−2, η = 2.7%). This demonstrates that, at 1 Sun light intensity on high surface area microwire arrays, earth-abundant electrocatalysts can provide performance comparable to noble-metal catalysts for photoelectrochemical hydrogen evolution. The formation of an emitter layer on the microwires yielded significant improvements in the open-circuit voltage of the microwire-array-based photocathodes relative to Si MW arrays that did not have a buried n+p junction. Analysis of the spectral response and light-intensity dependence of these devices allowed for optimization of the catalyst loading and photocurrent density. The microwire arrays were also removed from the substrate to create flexible, hydrogen-evolving membranes that have potential for use in a solar water-splitting device.

Characteristics of hydrogen evolution and oxidation catalyzed by Desulfovibrio caledoniensis biofilm on pyrolytic graphite electrode

Hydrogenase, an important electroactive enzyme of sulphate-reducing bacteria (SRB), has been discovered having the capacity to connect its activity to solid electrodes by catalyzing hydrogen evolution and oxidation. However, little attention has been paid to similar electroactive characteristics of SRB. In this study, the electroactivities of pyrolytic graphite electrode (PGE) coated with SRB biofilm were investigated. Two corresponding redox peaks were observed by cyclic voltammetry detection, which were related to the hydrogen evolution and oxidation. Moreover, the overpotential for the reactions decreased by about 0.2 V in the presence of the SRB biofilm. When the PGE coated with the SRB biofilm was polarized at 0.24 V (vs. SHE), an oxidation current related to the hydrogen oxidation was found. The SRB biofilm was able to obtain electrons from the −0.61 V (vs. SHE) polarized PGE to form hydrogen, and the electron transfer resistance also decreased with the formation of SRB biofilm, as measured by the non-destructive electrochemical impendence spectroscopy detection. It was concluded that the hydrogen evolution and oxidation was an important way for the electron transfer between SRB biofilm and solid electrode in anaerobic environment.

Hydrogen generation by hydrolysis of Al–Li–Bi–NaCl mixture with pure water

In the present work, the Al–Bi–Li mixtures were prepared by a milling processing, using NaCl as the milling-assisted agent, and the hydrogen evolution characteristics of the as-prepared Al-based mixtures with pure water were evaluated. The results showed that the addition of Li could significantly improve the hydrolysis rate of Al-based mixtures and increase the amount of generated hydrogen. When the amount of Li was increased up to 4 wt%, 1 g Al-based mixture could yield 1.38 SL hydrogen which was higher than that generated from pure Al and water. The powder X-ray diffraction analysis indicated that some new phases, namely BiLi 3 and AlLi, were formed during the milling process. The enhanced hydrolysis rate of Al-based mixtures was mostly attributed to the presence of these new phases because they might act as an active reaction center in water. The apparent activation energy calculated from the as-obtained hydrogen evolution kinetic data also supported such an explanation. The hydrolysis products of Al-based mixtures were Al(OH) 3 (bayerite), Bi and LiAl 2(OH) 7·2H 2O, whereas only AlOOH (boehmite) was observed for the system without addition of Li, indicating that the addition of Li did increase the hydroxyl ions concentration during the hydrolysis process.

High efficiency large area a‐SiGe:H based multi‐junction solar cells using MVHF

AbstractWe have developed high efficiency large area a‐Si:H and a‐SiGe:H multi‐junction solar cells using a Modified Very High Frequency (MVHF) glow discharge process. We investigated a‐SiGe:H deposition rate dependence of cell performance, and optimized MVHF a‐SiGe:H process at a deposition rate 2‐4 times that of a typical RF deposition. We conducted a comparative study for different cell structures, and compared the initial and stable performance and light‐induced degradation of solar cells made using MVHF and RF techniques. In additon to high initial efficiency, the MVHF cells also exhibit superior light stability, showing <10% degradation after 1000 hour of one‐sun light soaking at 50 °C. We also studied light‐induced defect level and hydrogen evolution characteristics of MVHF deposited a‐SiGe:H films and compared them with the RF deposited films (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High Efficiency Large Area a-Si:H and a-SiGe:H Multi-junction Solar Cells Using MVHF at High Deposition Rate

AbstractWe have developed high efficiency large area a-Si:H and a-SiGe:H multi-junction solar cells using a Modified Very High Frequency (MVHF) glow discharge process. We conducted a comparative study for different cell structures, and compared the initial and stable performance and light-induced degradation of solar cells made using MVHF and RF techniques. Besides high efficiency, the MVHF cells also demonstrate superior light stability, showing <10% degradation after 1000 hour of one-sun light soaking at 50 °C. We also studied light-induced defect level and hydrogen evolution characteristics of MVHF deposited a-SiGe:H films and compared them with the RF deposited films.

Behavior of hydrogen evolution of aqueous sodium borohydride solutions

Characteristics of hydrogen evolution from non-stabilized and alkali-stabilized sodium borohydride solutions were systematically studied in order to understand the fuel storage features of borohydride in fuel cell applications. The effects of the sodium borohydride concentration, the temperature of the hydrolysis reaction, the sodium metaborate concentration, and the continuous temperature control for alkali-stabilized sodium borohydride solutions on the hydrogen generation and yield were investigated. Temperature variation was the major parameter that affected the stability of sodium borohydride solutions with and without stabilizing agents during hydrogen storage.

Surface modification of semiconductor photoelectrode for improved solar cell performance

The investigation is focused on the synthesis of nanostructured TiO 2–CuO admixed photoelectrode and its use as a photoelectrode of high-efficiency PEC solar cells for hydrogen production. TiO 2, in the nanostructured form, has been prepared by hydrolysis of titanium(IV) isopropoxide solution. An improvement in the nanostructured TiO 2 photoelectrode carried out in the present work corresponds to admixing CuO to improve the spectral response. In the present study, photo-electrochemical (PEC) and hydrogen evolution characteristics of new types of ns-TiO 2–CuO admixed/Ti septum-based semiconductor septum photo-electrochemical (SC-SEP PEC) solar cell has been studied. The CuO admixed ns-TiO 2 exhibited a high photocurrent and photovoltage of 18.6 mA/cm 2 and 680 mV, respectively. The ns-TiO 2–CuO electrode exhibited a higher hydrogen gas evolution rate of 14.00 l/h m 2.

Preparation and Characterization of Electrolessly Deposited Platimum and Palladium Nanoparticles on Pyrolyzed Photoresist Films on Silicon Substrates

The effects of metal depositions on pyrolyzed photoresist films (PPF) grown on silicon substrates were investigated. A silicon chip, spin-coated with a positive photoresist was pyrolyzed through heating to form a PPF, or a conductive carbon film. For increasing periods of time, nanometersized metal particles of platinum and palladium were spontaneously deposited on conductive carbon films by immersion in solutions of 0.049% HF containing 100 ppm, 200 ppm, and 500 ppm concentrations of metal ions Pt2+ or Pd2+. Following each hour of deposition, the electrochemical behavior of the metal-deposited carbon films were investigated by cyclic voltammetry, utilizing a 0.1 M H2SO4 electrolyte system. The electron-transfer rates and characteristics of hydrogen evolution exhibited positive catalytic effects when the platinum and palladium nanoparticles were deposited on the carbon films. Scanning electron microscopy and energy-dispersive x-ray analysis were employed to characterize the surface morphology and distribution of metal nanoparticles on the PPF surface based on metal ion concentration and deposition time. The depositions of metal nanoparticles accelerate the electron transfer process, which could improve the efficiency and performance of PPF electrodes in the production of hydrogen fuel.

Semiconductor-septum photoelectrochemical solar cell for hydrogen production

In the present study, photo-electrochemical and hydrogen evolution characteristics of a new type of TiO 2(ns) and TiO 2(ns)–In 2O 3/Ti septum based semiconductor-septum photo-electrochemical (SC-SEP, PEC) solar cell has been studied. The SC-SEP cell in the configuration of SCE/1 M NaOH/TiO 2(ns)/Ti/H 2SO 4+K 2SO 4/Pt CE, Pt WE showed the photo-voltage and photo-current of 0.72 V and 8.6 mA/cm 2, whereas the SC-SEP cell employing In 2O 3 admixed TiO 2(ns) photo-electrode and having the configuration: SCE/1 M NaOH/TiO 2(ns)–In 2O 3/Ti/H 2SO 4+K 2SO 4/Pt CE, Pt WE, showed the photo-voltage and photo-current of 0.92 V and 14.6 mA/cm 2, respectively. The hydrogen gas evolution for the SC-SEP cell based on TiO 2(ns)/Ti photo-electrode was found to be 8.2 l/h m 2, on the other hand the In 2O 3 modified TiO 2(ns) exhibited a higher hydrogen gas evolution rate of 11.8 l/h m 2. Evidence and arguments have been put forward to show that the presence of In 2O 3 over TiO 2 makes the system posses the advantages of a colloidal photochemical system. The better performance of the new photo-electrode is thought to be due to improved spectral response and catalytic activity of In 2O 3 in regard to the hydrogen gas evolution kinetics.

Solar hydrogen production using semiconductor septum ( n- [formula omitted] and n- [formula omitted]) electrode based photoelectrochemical solar cells

In the present study, photoelectrochemical and hydrogen evolution characteristics of CdSe Ti and TiO 2 Ti based semiconductor-septum photoelectrochemical (SC-SEP, PEC) solar cell have been studied. The SC-SEP cell in the configuration of SCE, l M 3S//CdSe/Ti//5 M H 2SO 4, Pt(W), Pt(C), gave power output of 0.62 V and 11 mA cm −2, whereas the conventional Pt, 1 M 3S//CdSe/Ti, PEC cell gives power output of 0.64 V and 6 mA cm −2. The hydrogen evolution characteristics of SCE, l M 3S//CdSe/Ti//5 M H 2SO 4, Pt(W), Pt(C), exhibited a rate of 1.0 to 1.5 1 h −1 m −2 under an illumination intensity of 80 mW cm −2. The TiO 2 Ti septum based SC-SEP solar cell in the configuration of SCE, 1 M NaOH//TiO 2/Ti//5 M H 2SO 4, Pt(W), Pt(C), gives power output of 0.74 V and 14.5 mA cm −2 whereas the conventional Pt, 1 M NaOH//TiO 2/Ti, PEC solar cell gives power output of 0.7 V and 5 mA cm −2. The hydrogen evolution characteristics of TiO 2/Ti based SC-SEP cell measured in the configuration of SCE, 1 M NaOH//TiO 2/Ti//5 M H 2SO 4, Pt(W), Pt(C), gave a hydrogen evolution rate of 10–15 1 h −1 m −2 under an illumination intensity of 450 mW cm −2. It has been shown in the present investigation that TiO 2 Ti based SC-SEP solar cell is more stable and gives higher rate of hydrogen production compared to the CdSe Ti based SC-SEP cell. Further studies to optimize the stability and other conditions for the production of solar hydrogen using these SC-SEP solar cells have been outlined.