Hydrogen Evolution In Acidic Media Research Articles

Nanocomposite of Graphene–Phosphorene Structures with Cobalt Phosphide as an Effective Electrocatalyst for Hydrogen Evolution in Acidic Medium

Nanocomposite of Graphene–Phosphorene Structures with Cobalt Phosphide as an Effective Electrocatalyst for Hydrogen Evolution in Acidic Medium

Strategic design of NiS2/Co3S4 heterojunction for enhanced electrocatalytic hydrogen evolution in acidic media

The construction of heterogeneous interface significantly contributes to the boosted electrocatalytic activity for hydrogen evolution reaction (HER). This enhancement is achieved through the modulation of the electronic structure, facilitation of electron redistribution, and optimization of the electrocatalyst's chemisorption towards the reaction intermediates. Herein, NiS2/Co3S4 heterojunction was synthesized using a straightforward one-pot hydrothermal method, and the impact of heterogeneous interface on the electrocatalytic HER performances was investigated. The heterogeneous interface and strengthened interfacial effects between NiS2 and Co3S4 were confirmed by HRTEM and XPS. The NiS2/Co3S4 heterojunction demonstrate significantly enhanced HER performance in acidic solutions, owing to their clever structural design and the robust interfacial coupling effects within the heterogeneous interface structure, surpassing that of single-component NiS2 materials. The optimum NiS2/Co3S4 heterojunction presents a low overpotential of 253 mV and a Tafel slope of 62.0 mV dec−1 at 10 mA cm−2 toward HER. Density functional theory (DFT) calculation indicates that NiS2/Co3S4 heterostructure exhibit lower ΔGH* values compared to NiS2 and Co3S4. This suggests that the creation of heterogeneous interface can significantly optimize the adsorption capacity for hydrogen intermediates, thereby enhancing the HER in acidic media.

Efficient fabrication of Ni-S/MoS2 hybrid nanoflowers for improved hydrogen evolution in acid media

It is significant to develop highly efficient and cost-effective hydrogen evolution reaction (HER) electrocatalysts. Herein, we propose an efficient fabrication of Ni-S/MoS2 hybrid nanoflowers grown on Ti foil (Ni-S/MoS2/Ti) via a simple one-step hydrothermal reaction method. When used as a HER catalyst, Ni-S/MoS2/Ti exhibits superior HER performances compared with MoS2 grown on Ti foil (MoS2/Ti) and Ni-S adsorbed on Ti foil (Ni-S/Ti) counterparts in acid media, due to its increased active surface area, enhanced electrical conductivity and synergistic effects from the coexistence of bimetallic sulfides. Additionally, Ni-S/MoS2/Ti demonstrates good HER durability, resisting the acid corrosion during HER process.

Bimetallic PtCu/C Catalysts for Glycerol Assisted Hydrogen Evolution in Acidic Media

Bimetallic PtCu/C Catalysts for Glycerol Assisted Hydrogen Evolution in Acidic Media

Bimetallic PtCu/C Catalysts for Glycerol Assisted Hydrogen Evolution in Acidic Media

The Front Cover shows an artistic close-up of an electrochemical cell illustrating the oxidation of glycerol as an alternative approach to efficient hydrogen production. The PtCu catalyst investigated in the research article is visible in the zoom window in the upper part of the image. More information can be found in the Research Article by S. D. Mürtz et al.

Bimetallic PtCu/C Catalysts for Glycerol Assisted Hydrogen Evolution in Acidic Media

Glycerol electrooxidation is a promising alternative to oxygen evolution as an anodic reaction for efficient hydrogen production. However, the performance of electrocatalysts in this reaction is still limited by CO poisoning and products of lower value form due to C−C cleavage. In this study, PtCu/C catalysts with different metal ratios were investigated for glycerol electrooxidation in acidic media. The addition of Cu to the benchmark Pt/C catalyst increased the activity, productivity, as well as stability due to electronic and structural effects. The best performer Pt7Cu3/C showed an increase in mass activity of 56 %. Lower accumulation of intermediates was proven in electrolysis experiments, leading to an increased selectivity of 90 % to valuable C3-products. The combined methodology of comprehensive electrochemical characterization and application in electrolysis experiments provides a practical approach for improving glycerol assisted hydrogen production addressing major challenges such as CO poisoning and stability.

Hydrogen Evolution Volcano(es)—From Acidic to Neutral and Alkaline Solutions

As the global energy crisis continues, efficient hydrogen production is one of the hottest topics these days. In this sense, establishing catalytic trends for hydrogen production is essential for choosing proper H2 generation technology and catalytic material. Volcano plots for hydrogen evolution in acidic media are well-known, while a volcano plot in alkaline media was constructed ten years ago using theoretically calculated hydrogen binding energies. Here, for the first time, we show that the volcano-type relationships are largely maintained in a wide range of pH values, from acidic to neutral and alkaline solutions. We do this using theoretically calculated hydrogen binding energies on clean metallic surfaces and experimentally measured hydrogen evolution overpotentials. When metallic surfaces are exposed to high anodic potentials, hydrogen evolution can be boosted or significantly impeded, depending on the type of metal and the electrolyte in which the reaction occurs. Such effects are discussed here and can be used to properly tailor catalytic materials for hydrogen production via different water electrolysis technologies.

Conductive and Ultrastable Covalent Organic Framework/Carbon Hybrid as an Ideal Electrocatalytic Platform.

Developing covalent organic frameworks (COFs) with good electrical conductivity is essential to widen their range of practical applications. Thermal annealing is known to be a facile approach for enhancing conductivity. However, at higher temperatures, most COFs undergo amorphization and/or thermal degradation because of the lack of linker rigidity and physicochemical stability. Here, we report the synthesis of a conductive benzoxazole-linked COF/carbon hybrid material (BCOF-600C) by simple thermal annealing. The fused-aromatic benzoxazole and biphenyl building units endow the resulting COF with excellent physicochemical stability against high temperatures and strong acids/bases. This allows heat treatment to further enhance electrical conductivity with minimal structural alteration. The robust crystalline structure with periodically incorporated nitrogen atoms allowed platinum (Pt) atoms to be atomically integrated into the channel walls of BCOF-600C. The resulting electrocatalyst with well-defined active sites exhibited superior catalytic performance toward hydrogen evolution in acidic media.

Ultrasmall Pt2Sr alloy nanoparticles as efficient bifunctional electrocatalysts for oxygen reduction and hydrogen evolution in acidic media

Electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic media are vital for the applications of renewable energy electrolyzers. However, the low mass activity of noble Pt urgently needs to be improved due to the strong binding energetics of oxygen species (*O) with Pt sites. Here we report fine PtxSr alloy (~2 nm) supported on N-doped carbon (NC) pyrolyzing from ZIF-8 as bifunctional electrocatalysts toward ORR and HER in acidic media. The representative Pt2Sr/NC exhibits an onset potential of 0.94 V vs. RHE and half-wave potential of 0.84 V toward ORR, and a low overpotential of 27 mV (10 mA cm−2) toward HER, respectively. Significantly, the mass activities of Pt2Sr/NC are 6.2 and 2.6 times higher than that of Pt/C toward ORR (at 0.9 V) and HER (at −30 mV), respectively. Simultaneously, Pt2Sr/NC possesses a retention rate of 90.97% toward acidic ORR after 35000 s of continuous operation. Through density functional theory (DFT) calculations and X-ray photoelectron spectroscopy analysis, the incorporation of Sr into Pt forming Pt2Sr alloy redistributes the electronic structures of Pt–Pt bonds, changing the rate-determining step for the ORR on Pt sites from the formation of *OH from *O to the generation of *OOH along with decreasing the energy barrier, which is also confirmed by the downshift of d band center. Meanwhile, the downshift of d band center also leads to the optimization of the adsorption energy (H*) with Pt, significantly improving Pt2Sr/NC toward HER.

Double layer lanthanide –Pt/TiO2 nanotube arrays electrode as a cost-highly efficient electrocatalyst for hydrogen evolution in acid media

Self-organized anodic double layer TiO2 nanotube arrays (TNTAs) were sensitized by an electrochemical anodization process on a Ti sheet with a two-step anodization method. The prepared sample, followed by hydrothermal treatment with Nd(NO3)3 and/or Gd(NO3)3 and/or PtCl4 solution at 180 °C for 2 h, produced Nd-Pt-TNTAs, Gd-Pt-TNTAs, Nd-Gd-Pt-TNTAs and Pt-TNTAs. The morphological and structural properties were studied by SEM, XRD and Raman spectra techniques. The hydrogen evolution reaction (HER) performance on Lanthanides-Pt-TNTAs was investigated using the Tafel linear polarization technique. The calculated values of the activation energy are in good agreement with the trend in catalytic activity. The excellent performance of doped TNTAs with low activation energy (E a) is due to the formation of an excitation energy level below the conduction band of TiO2 from the binding of electrons with oxygen vacancies decreasing the excitation energy resulting in robust electrocatalytic activity. The very low value of E a for Nd-Gd-Pt-TNTAs (2.02 kJ/mol) compared to other electrochemical catalysts used for hydrogen evolution reactions containing titanium nanotubes was achieved for the first time. This makes the Lanthanides –Pt-TNTAs prepared in the present work optimal catalysts for electrodes and promising for applications in fuel cells or as water splitting materials. Highlights Synthesis of self-organized anodic double layer TiO2 nanotube arrays (TNTAs) on a Ti sheet with a two-step anodization method. Nd, Gd, Pt were deposited on anodic TNTAs arrays by hydrothermal method. The HER mechanisms on Lanthanides-Pt-TNTAs in acidic media has been discussed. The order of catalytic activity based on the values of activation energy was Nd-Gd-Pt-TNTAs > Gd-Pt-TNTAs > Nd-Pt-TNTAs > Pt-TNTAs > undoped TNTAs.

Facile synthesis of SnO2 nanostructures for enhanced electrochemical hydrogen evolution reaction

Material selection for electrochemical hydrogen evolution in acidic medium is of great interest and remains a challenging task. Tin oxide (SnO2) is a distinguishable catalyst due to its high stability in acidic electrolyte medium, excellent charge transport properties and abundant active sites. Herein, we demonstrate a facile solvothermal route to synthesize SnO2 1D porous nanotubes and microplates. Moreover, the as-synthesized SnO2 nanostructures were used as efficient electrocatalysts for HER activity in acid media. The SnO2 nanotubes are found to be higher HER activity than microplates. The SnO2 nanotubes exhibit a lower overpotential of 147.6 mV, which is not only lower than other electrocatalysts but also comparable with benchmark Pt/C. In addition, it shows excellent stability with a negligible decrease in current density after 10 h chronoamperometric test in acid electrolyte. Thus this result highlights its potential for the development of electrolyzer.

Electroanalysis of unnatural base pair content in plasmid DNA generated in a semi-synthetic organism

While standard Watson-Crick base pairing normally involves hydrogen bonds that join size complementary nitrogenous heterocycles, certain unnatural base pairs (UBP) can support replication, transcription, and translation, including these in semi-synthetic organisms (SSO), using size complementarity alone. In this paper we show that the UBPs can be analyzed electrochemically as components of ribo- or 2′-deoxyribonucleosides, corresponding (2’-deoxy)triphosphates, as well as incorporated into DNA. Here, performance of the electrochemical methods profits from the ability of the unnatural bases 5SICS and TPT3 adsorbed at the surface of a mercury electrode to catalyze hydrogen evolution in acidic media. This allows semi-quantitative detection of single UBP within plasmid DNA generated in a SSO. This electrochemical approach provides new way for direct, fast, and low cost UBP analysis and can supplement or replace currently used methods of UBP detection.

Towards thermoneutral hydrogen evolution reaction using noble metal free molybdenum ditelluride/graphene nanocomposites

The development of efficient electrocatalysts for hydrogen generation is an essential task to meet future energy demand. In recent years, molybdenum ditelluride (MoTe2) has triggered incredible research interests due to intrinsic nontrivial band gap with promising semi-metallic behaviors. In this work, 2D MoTe2 nanosheets have been synthesized uniformly on graphene substrate through ultra-fast microwave-initiated approach, that shows a superior hydrogen evolution in acidic medium with low overpotential (~150 mV), low activation energy (8.4362 ± 1.5413 kJ mol−1), along with a Tafel slope of 94.5 mV/decade. Interestingly, MoTe2/graphene exhibits the enhanced electrocatalytic stability during the long cycling test, resulting an increase in specific surface area of catalyst materials. Moreover, the results from periodic plane-wave density functional theory (DFT) indicate that, the best active sites are the corner of a Mo-atom and a critical bifunctional site comprised of adjacent Mo and Te edge atoms. Furthermore, the corresponding volcano plot reveals the near thermoneutral catalytic activity of MoTe2/graphene for hydrogen generation.

Co@N-doped carbon nanomaterial derived by simple pyrolysis of mixed-ligand MOF as an active and stable oxygen evolution electrocatalyst

Design and synthesis of cost effective, non-noble and efficient electrocatalysts for oxygen evolution reaction (OER) has prospective in the development of various renewable energy storage and conversion devices. We developed metallic cobalt encased N-doped carbon hybrid nanomaterial with remarkable electrochemical activity from a three-dimensional cobalt (II) based N-containing MOF as a sacrificial template by carbonization. All the carbonized materials have been characterized by various analytical methods to establish the structural and morphological integrity. N-doped graphitic carbon embedded with metallic cobalt (CoNC-900) revealed promising electrochemical activity towards OER in alkaline and hydrogen evolution in acidic media with good stability. Among the series of carbonized MOF material CoNC-900 is designated as highly efficient electrode materials with low overpotential/Tafel slope and superior stability for OER. Standard current density of 10 mA cm−2 was attained at a smaller overpotential (210 mV) by CoNC-900 compared to state-of-the-art RuO2 electrocatalyst (280 mV) indicating OER kinetics response is significantly higher showing the superior activity outperforming most reported electrocatalysts. In view of the best OER performance, experiments have been performed to gauge the electrochemically active surface area, stability/durability and charge transfer resistance (Rct), which also supports the efficient electrocatalytic performance observed in CoNC-900.

Nanostructured Ni2SeS on Porous-Carbon Skeletons as Highly Efficient Electrocatalyst for Hydrogen Evolution in Acidic Medium.

Nickel dichalcogenides have received extensive attention as promising noble-metal-free nanocatalysts for a hydrogen evolution reaction. Nonetheless, their catalytic performance is restricted by the sluggish reaction kinetics, limited exposed active sites, and poor conductivity. In this work, we report on an effective strategy to solve those problems by using an as-designed new porous-C/Ni2SeS nanocatalyst with the Ni2SeS nanostubs anchored on with porous-carbon skeletons process. On the basis of three advantages, as the enhancement of the intrinsic activity using the ternary sulfoselenide, increased number of exposed active sites due to the 3D hollow substrate, and increased conductivity caused by porous-carbon skeletons, the resulting porous-C/Ni2SeS requires an overpotential of only 121 mV at a current density of 10 mA cm-2 with a Tafel slope of 78 mV dec-1 for hydrogen evolution in acidic media and a good long-term stability. Density functional theory calculations also show that the Gibbs free energy of hydrogen adsorption of the Ni2SeS was -0.23 eV, which not only is close to the ideal value (0 eV) and Pt reference (-0.09 eV) but also is lower than those of NiS2 and NiSe2; large electrical states exist in the vicinity of the Fermi level, which further improves its electrocatalytic performance. This work provides new insights into the rational design of ternary dichalcogenides and hollow structure materials for practical applications in HER catalysis and energy fields.

Ultrastable molybdenum disulfide-based electrocatalyst for hydrogen evolution in acidic media

Despite the incredible success in reducing the overpotential of nonprecious catalysts for acidic hydrogen evolution reaction (HER) in the past few years, the stability of most platinum-free electrocatalysts is still poor. Here, we report an ultrastable electrocatalyst for acidic HER based on two-dimensional (2D) molybdenum disulfide (MoS2) doped with trace amount of palladium (<5 μg cm−2), which creates sulfur vacancies (S-vacancies). The optimized catalyst shows stable operation over 1000 h at 10 mA cm−2 with overpotential of 106 mV. The MoS2 catalyst is stabilized on a defective vertical graphene support, where the strong interaction at the 2D-2D interface increases the adhesion between the catalyst and the support. Palladium (Pd) doping generates rich sulfur vacancies in MoS2 that have a twofold role: (1) increasing hydrogen adsorption energy, which enhances activity; and (2) further increasing the adhesion between graphene support and defective MoS2, and thus enhancing stability. Complementary theoretical studies reveal the reaction pathways for substitutional doping, where the Mo-vacancy sites are prior to be doped by Pd. Our work thus offers a strategy for making stable, efficient, and earth-abundant HER catalysts with strong potential to replace platinum for PEM electrolysis.

Spectroscopic, optical sensing and RedOx behaviour of 1, 5-diphenylcarbazone

The optical sensing and redox properties of 1, 5-diphenylcarbazone (dpc) towards some divalent metal ions (Co(II), Zn(II), and Pb(II)) were investigated by absorption spectroscopy, cyclic and square wave voltammetries, and the results supported by density functional calculations (DFT). Experimental absorption spectra of dpc is characterized by the HOMO→LUMO intra-molecular inter-ring π to π* charge transfer transition in addition the lower energy π to π* and less probable n to π* transitions of the NN and CO moieties. The optical sensitivity of this system, originates from the ability of the n-electrons on the azo or CO moieties, or the acidic hydrogens of the amide and amine groups to form inter-molecular interactions with other molecules and ions. Voltammetric analyses revealed that both the azo and amidic moieties are reduced via EC mechanisms in CH3CN, and the molecule is not capable of stabilizing the reduced states of the divalent ions, hence, electrocatalytic hydrogen evolution in acidic media was not observed for the cobalt(II) dpc system.

Ultrafine Ruthenium Oxide Nanoparticles Supported on Molybdenum Oxide Nanosheets as Highly Efficient Electrocatalyst for Hydrogen Evolution in Acidic Medium

AbstractEngineering of efficient, robust and inexpensive Pt‐free catalysts for the hydrogen evolution reaction has drawn great attention, and there is a rapidly growing demand for electrochemical water‐splitting reactions. Here, we report, for the first time, synthesis of ruthenium oxide nanoparticles supported on molybdenum oxide nanosheets (MoO3@RuO2). This composite catalyst was prepared sonochemically, followed by calcination of the product in air at 400 °C for one hour. The as‐synthesized MoO3@RuO2 composite catalyst was used to explore the electro‐catalytic hydrogen evolution reaction in acidic medium. Notably, compared to MoO3 or RuO2, the composite exhibited high exchange current density of 0.57 mA cm−2, and a current density of 10 mA cm−2 was achieved at low overpotential of 110 mV in 0.5 M H2SO4. The Tafel slope of the MoO3@RuO2 catalyst was 62 mV dec−1 and it showed excellent stability. This remarkable performance can be attributed to the synergetic effect generated by the strong interaction between MoO3 nanosheets and RuO2 nanoparticles, which resulted in enhanced long‐term stability as well.

The influence of addition of iridium-oxide to nickel-molybdenum-oxide cathodes on the electrocatalytic activity towards hydrogen evolution in acidic medium and on the cathode deactivation resistance

The influence of addition of Ir-oxide into Ni-Mo-oxide cathodes on the electrocatalytic activity of the hydrogen evolution reaction in acidic media was investigated. It was found that as the Ir-oxide content increased, the electrocatalytic activity towards hydrogen evolution also increased. This was attributed to the following two effects: the increase in the number of Ir surface sites and to the possible modification of the electronic structure of the material. Long-term electrolysis experiments confirmed high deactivation resistance of the Ni-Mo-Ir-oxide cathodes. It was also demonstrated that it is possible to in-situ reactivate the electrodes, making them potentially good cathode candidates for water electrolysis in the acidic medium.

NiCoFe alloy multishell hollow spheres with lattice distortion to trigger efficient hydrogen evolution in acidic medium

NiCoFe alloy multishell hollow spheres supported on graphitic carbons with lattice defects are prepared, and they show high activity for hydrogen evolution in acidic medium.