Hydrogen Adsorption Desorption Research Articles

Direct synthesis of PtNi coated with Ni3B for efficient electrochemical hydrogen evolution from seawater.

The design of a protective electron-rich surface is an ideal route to enhance the performance of catalysts. Due to the higher work function of Ni3B, facile-directed electron transport occurs from PtNi to Ni3B to enrich electron density on the surface of the Ni3B shell. This process increases hydrogen adsorption-desorption kinetics and mitigates Cl- corrosion.

Deciphering the surface electrochemical reconstruction of ruthenium-cobalt-nickel phosphide for efficient high-current hydrogen evolution and overall water splitting.

Development of efficient and stable bifunctional transition metal phosphide catalysts is critical for advancing hydrogen production technologies. Herein, RuCo co-doped Ni8P3 (RuCoNiP) was designed and synthesized by one-step electrodeposition for Ni electronic structure modulation, and evolved to RuCoNiP@α-Ni(OH)2 and RuCoNiP@Co/Ni(OH)x heterointerfaces by self-assembled reconstruction during HER and OER processes, respectively. RuCoNiP@α-Ni(OH)2 enhances HER activity (305.8mV@-1000mAcm-2) and stability (100h@-1000mAcm-2) by weakening OH* and H* competitive adsorption. Density functional theory (DFT) calculations revel that the ΔGH* of Ni site (RuCoNiP) is reduced by the assignment of a large number of Ni d-states at the Fermi level by RuCo doping, which synergistically interacts with the enhanced adsorption of α-Ni(OH)2 to OH*, resulting in a lower energy barrier for hydrogen adsorption-desorption. Moreover, RuCoNiP@Co/Ni(OH)x relies on M(OH)x to enhance the activity (351.4mV@1000mAcm-2) and stability (100h@1000mAcm-2) of OER. Dual-electrode system RuCoNiP@α-Ni(OH)2//RuCoNiP@Co/Ni(OH)x demonstrates an ultra-low battery voltage (1.95V@1000mAcm-2) and excellent stability (50h@1000mAcm-2). This efficient synthetic strategy and the self-assembled heterojunction structure offer a promising path for developing efficient overall water-splitting catalysts.

Impact of the Cathode Platinum Distribution on the Proton Transport Resistance Measurement in a PEMFC

The cathode of a proton exchange membrane fuel cell (PEMFC) could have inhomogeneous platinum distribution through its thickness either by design (e.g., graded Pt loading electrodes) or as a result of degradation (e.g., Pt dissolution and migration to the membrane) [1,2]. The assessment of electrode properties such as inherent proton transport resistivity with electrochemical impedance spectroscopy (EIS) could be impacted by this inhomogeneity. Regarding protonic resistivity in the cathode, typically a transmission line model is fit to the corresponding EIS spectrum collected in the H2/N2 environment [3]. However, the model assumes a homogeneous distribution of capacitance and proton resistance through the electrode thickness and does not account for the inhomogeneity in Pt distribution. In this study, a bilayer electrode model system with variation in Pt loading is proposed to investigate the corresponding EIS spectrum as a function of Pt loading distribution in the cathode. 10 and 40wt% Pt on Vulcan were used to make low- and high-loading catalyst layers with a constant ionomer-to-carbon ratio of 0.85, which is supposed to result in similar proton transport resistivity in all designed electrodes. Artificially designed bilayer electrode structures of Low-Low, Low-High, High-Low, and High-High (first term: loading near membrane and second term: loading near the gas diffusion layer) have been successfully fabricated to simulate the cathode layer with homogeneous and heterogenous Pt mass loading through the electrode thickness. Potentiostatic EIS spectra of the bilayers at 0.45V bias potential revealed similar Rp for all samples (Avg. 51.7 Ω.cm2), while the measured Rp at 0.2V deviated by 22% for the High-Low and 55% for the Low-High sample from the corresponding value at 0.45V. Homogeneous bilayers maintained similar Rp at both bias potentials. Considering the cyclic voltammogram of the samples, the total capacitance is highly affected by a pseudo capacitive contribution from the Pt surface at potentials < 0.35V (Hydrogen adsorption-desorption) and > 0.65 (Pt surface oxidation). Even though the total capacitance is similar for High-Low and Low-High samples, the EIS spectra collected at 0.2V suggest that the distribution of capacitance through the electrode thickness can highly impact the spectra and corresponding Rp estimate.

Acid Modified Carbon Support with Proton Conductive Properties for Polymer Electrolyte Membrane Fuel Cell Applications

Proton exchange membrane fuel cell (PEMFC) are one of highly efficient electrochemical energy conversion technologies, with a potential to replace conventional fossil-fueled power generators for vehicles and stationary applications. One of the challenges for widespread use of PEMFC is to minimize the amount of platinum (Pt) to lower the cost of PEFCs. Therefore, optimizing electrocatalyst design to improve Pt mass activity is required. In the conventional PEMFC electrocatalyst, the proton conductive polymers such as Nafion are contained to transport protons to the Pt surface. However, the main problem of Nafion in catalyst layer (CL) is the inhomogeneously covered on commercial catalyst of Vulcan/Pt (CB/Pt) surface leads a low proton conductivity or high O2 diffusion resistance. Furthermore, the SO3 − groups of the polymers are strongly adsorbed onto the Pt surface and decreasing Pt active sites to lower the catalytic activity. Hence, it’s necessary to develop a new CL without using ionomer (Nafion).An acid modified carbon support with proton conductive properties was considered for PEMFC applications. In our previous study, we synthesized a high-density -SO3H modified carbon support (named SCB) by covalent bonding and loaded Pt on SCB (SCB/Pt) to conductive proton. Attained a higher O2 diffusivity at high current density range because without Nafion added [1]. However, this method of destroying the sp2 structure of carbon has the problem of reducing the durability and electrical conductivity of carbon. In this work, we changed the acid modify carbon method from chemical modification to physical modification which using proton conductivity polymer adsorb on carbon surface to conductive proton. Polybenzimidazole (PBI) having a side chain of trifluorosulfonimide (PBI-TFSI) was chosen as a proton conductor adsorbed on carbon surface because PBI-TFSI was reported to have high proton conductivity [2].In this study, instead of adding Nafion as a proton conductor after loading Pt on carbon support, Pt is directly loaded on carbon support coated with PBI-TFSI to fabricate novel catalyst, CB/PBI-TFSI/Pt, and CL was fabricated. Absence of ionomer is expected to improve O2 diffusivity in the CL and also avoid specific adsorption of SO3 − groups on the Pt surface. Principal experiment of this study is synthesis composite, characterize the catalyst properties and evaluate of electrochemical cell performance. As the control catalyst, commercial CB/Pt (TKK10V30E) was used.The PBI-TFSI content of CB/PBI-TFSI was estimated by CHN elemental analysis, which revealed that its C: H: N atomic ratio was 0.37: 95.59: 0.61. Considering that all the nitrogen was originating from PBI-TFSI, and side chain of graft ratio is 73.25%, the PBI-TFSI content of CB/PBI-TFSI was determined to be 4.5%. Thermal stability of the catalysts was compared by thermogravimetric analysis (TGA). As the results, CB/PBI-TFSI displayed a one-step weight loss similar to that of CB with a degradation temperature around 650°C, while SCB started to drop at 550°C [1]. This superior thermal stability of CB/PBI-TFSI compared to SCB was because sp3 defect was not introduced by using polymer wrapping method, while chemical modification method used to SCB introduced sp3 defects. Such a good thermal stability is expected to offer the high electrochemical durability in the PEMFC operation. The Pt loading of CB/PBI-TFSI/Pt determined from the TGA weight residue at 900 °C was 30 wt% comparable with CB/Pt. The size of the Pt nanoparticles in both CB/PBI-TFSI/Pt and CB/Pt was analyzed by TEM. The determined sizes of the Pt nanoparticles in CB/PBI-TFSI/Pt and CB/Pt were 2.04 ± 0.3 and 2.10 ± 0.2 nm, respectively. The comparable Pt loading and size of Pt nanoparticles in CB/Pt and CB/PBI-TFSI/Pt mean that these samples can be used in comparative studies.For the electrochemical characterization, the electrochemical active surface area (ECSA) was determined using the hydrogen adsorption/desorption (HAD) method and the polarization curves are operated using H2/air. The results indicated that the cell of CB/PBI-TFSI/Pt exhibits activity over 1.0 A/cm2 current density even without ionomer. However, compare with commercial catalyst of CB/Pt with Nafion, CB/PBI-TFSI/Pt still shows a lower cell performance because the higher resistance between Nafion membrane and CL. Additional improvements to the proton conductivity of the acid-grafted carbon support and the reduction of the interfacial resistance between PEM and CL could potentially further increase the PEMFC performance. O2 diffusivity as well as the fuel cell operation under the low humidity will also discuss.[1] Yoshihara R, Wu D, Phua YK, Nagashima A, Choi E, Jayawickrama SM, et al. Journal of Power Sources. 2022;529:231192.[2] Han H, Miura H, Motoishi Y, Tanaka N, Fujigaya T. Polymer Journal. 2021;53:1403-11. Figure 1

Crystalline/Amorphous Interface Engineering and d-sp Orbital Hybridization Synergistically Boosting the Electrocatalytic Performance of PdCu Bimetallene toward Formic Acid-Assisted Overall Water Splitting.

Advanced electrocatalysts capable of bifunctional catalysis for formic acid oxidation (FAOR) and hydrogen evolution reaction (HER) have garnered significant attention due to their exceptional energy efficiency. In this research, we have meticulously designed a PdCu bimetallene characterized by numerous crystalline/amorphous (c/a) interfaces and robust d-sp orbital hybridization, achieved by integrating the p-block metalloid boron within the PdCu matrix (B-PdCu-c/a). The B-PdCu-c/a bimetallene revealed a multitude of surface atoms and unsaturated defect sites, offering abundant catalytic active sites and an optimized electronic structure. The B2-PdCu-c/a exhibited the best performance in FAOR and HER, achieving a mass activity of 1106 mA mgcat-1 and an overpotential of 52 mV, respectively. Significantly, the two-electrode configuration of B2-PdCu-c/a∥B2-PdCu-c/a attained a low cell voltage of 0.19 V at 10 mA cm-2 during formic acid-assisted overall water splitting. Density functional theory (DFT) calculations indicated that c/a interface engineering and d-sp orbital hybridization synergistically optimized the electronic configuration of pristine PdCu bimetallene. This led to an elevation of the d-band center and an accumulation of charge at the c/a interface, which enhanced the adsorption of intermediates, facilitated C-H bond cleavage, and balanced the adsorption-desorption of hydrogen, thereby improving electrocatalytic activities for FAOR and HER, respectively. This study not only presents a viable strategy for effectively tuning the electronic configuration of bimetallene but also offers valuable insights into the development of electrocatalysts.

Thermal Rates and High-Temperature Tunneling from Surface Reaction Dynamics and First-Principles.

Studying dynamics of the dissociative adsorption and recombinative desorption of hydrogen on copper surfaces has shaped our atomic-scale understanding of surface chemistry, yet experimentally determining the thermal rates for these processes, which dictate the outcome of catalytic reactions, has been impossible so far. In this work, we determine the thermal rate constants for dissociative adsorption and recombinative desorption of hydrogen on Cu(111) between 200 and 1000 K using data from reaction dynamics experiments. Contrary to current understanding, our findings demonstrate the predominant role of quantum tunneling, even at temperatures as high as 400 K. We also provide precise values for the reaction barrier (0.619 ± 0.020 eV) and adsorption energy (0.348 ± 0.026 eV) for H2 on Cu(111). Remarkably, the thermal rate constants are in excellent agreement with a first-principles quantum rate theory based on a new implementation of ring polymer molecular dynamics for reactions on surfaces, paving the way to discovering better catalysts using reliable and efficient computational methods.

Effects of Heteroatom Doping on the Electrochemical Hydrogen Uptake and Release of Pd-Decorated Reduced Graphene Oxide.

Heteroatom doping has been widely recognized as a key strategy for improving the electrochemical properties of graphene-based materials for hydrogen storage. However, a precise understanding of how heteroatom doping influences catalytic performance, specifically regarding the intricate effects of doping-induced electron redistribution, has been lacking. Here, we report on a comprehensive exploration of the electrochemical performance enhancement in Pd-decorated reduced graphene oxide (rGO) nanocomposites through fluorine (F) or nitrogen (N) doping. Various analytical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) were employed to thoroughly characterize the synthesized nanocomposites. The findings revealed that either F or N doping effectively addressed clustering issues of Pd nanoparticles formed on the rGO surface, resulting in improved homogeneity of Pd distribution. Electrochemical studies provided crucial insights into hydrogen adsorption-desorption behaviors. The heteroatom doped nanocomposites, Pd/N-rGO and Pd/F-rGO, exhibited superior electrochemical performance, which can be attributed to the increase of the active sites due to the N-/F-doping, respectively. The hydrogen discharge capacities of Pd/N-rGO (80.9 mAh g-1) and Pd/F-rGO (25.0 mAh g-1) nanocomposites were determined to be over 4.0 and 1.2 times higher than that of the Pd/rGO (20.1 mAh g-1), respectively. The distinctive electrochemical performances observed between the two types of heteroatom-containing nanocomposites highlight the subtle structural modifications of Pd nanoparticles as the key factor influencing performance. This research contributes essential knowledge to the evolving field of hydrogen storage materials, emphasizing the promising potential of heteroatom-doped Pd-decorated rGO nanocomposites for advancing clean and sustainable energy solutions.

Hydrogen Storage Using Platinum‐Supported Ceria Dispersed on Activated Carbon

ABSTRACTIn the current work, carbon materials were used in the hydrogen adsorption process, specifically as carbons doped with platinum dispersed on ceria. The textural characterization results of the prepared samples and the starting carbon showed the presence of both micro‐ and mesopores. On the other hand, it has been observed that the specific areas were inversely proportional to the CeO2 loading. In addition, the amount of adsorbed hydrogen increased after doping the carbon with platinum and, even more, when the carbon was doped with Pt dispersed on ceria (2.2 mg/g at 25°C and 30 bar). However, there was a ceria optimum from which the adsorption capacity decreased (10% wt). The results of temperature‐programmed desorption (TPD) of hydrogen indicated a high affinity between Pt and H2 that enhanced H2 adsorption process by establishing chemical bonds between the metal particles and H2. Precisely, the presence of metallic Pt particles dispersed on ceria considerably promotes the spillover process of hydrogen on carbon. This can be confirmed by hydrogen adsorption–desorption isotherms, that showed that complete desorption of chemisorbed hydrogen required an increase of temperature.

Prediction of the catalytic mechanism of hydrogen evolution reaction enhanced by surface oxidation on FCC_CoCrFeNi and Co0.35Cr0.15Fe0.2Mo0.1Ni0.2 multi-principal element alloys based on site preference

Some multi-principal element alloy (MPEA) catalysts may exhibit the ability to promote the hydrogen evolution reaction (HER) and maintain stability under acidic conditions. Here, we investigated the impact of ordered behavior and surface oxidation of FCC_CoCrFeNi and Co0.35Cr0.15Fe0.2Mo0.1Ni0.2 MPEAs on HER performance through first-principles calculations. The ordering behaviors of MPEAs were described using L12_AuCu3 sublattice model and the predicted site occupying fractions (SOFs). And we found that the catalytic activity of single intermediate *H at top or bridge adsorption sites surpassed that at the hollow site. However, the hollow site exhibits strong adsorption towards *H, resulting in the transfer of *H from other sites to hollow site. Meanwhile, compared to those containing only hydrogen, MPEAs with both hydrogen and oxygen exhibit lower overpotentials, primarily due to oxygen facilitating hydrogen adsorption and subsequent desorption from MPEA surfaces, thus, such fundamental finding highlights the beneficial role of alloy surface oxidation in promoting HER performance. Furthermore, the overpotential values of the three slab models based on SOFs are similar, demonstrating considerably consistent atomic distribution behaviors, thereby better reflecting the overall catalytic performance of ordered MPEAs. These explorations bring new insights into the ordered behavior and surface oxidation of MPEAs in HER catalysis.

Design of a new nanocomposite based on Keggin-type [ZnW12O40]6− anionic cluster anchored on NiZn2O4 ceramics as a promising material towards the electrocatalytic hydrogen storage

Extensive research efforts have been dedicated to developing electrode materials with high capacity to address the increasing complexities arising from the energy crisis. Herein, a new nanocomposite was synthesized via the sol–gel method by immobilizing K6ZnW12O40 within the surface of NiZn2O4. ZnW12O40@NiZn2O4 was characterized by FT-IR, UV–Vis, XRD, SEM, EDX, BET, and TGA-DTG methods. The electrochemical characteristics of the materials were examined using cyclic voltammogram (CV) and charge–discharge chronopotentiometry (CHP) techniques. Multiple factors affecting the hydrogen storage capacity, including current density (j), surface area of the copper foam, and the consequences of repeated cycles of hydrogen adsorption–desorption were evaluated. The initial cycle led to an impressive hydrogen discharge capability of 340 mAh/g, which subsequently increased to 900 mAh/g after 20 cycles with a current density of 2 mA in 6.0 M KOH medium. The surface area and the electrocatalytic characteristics of the nanoparticles contribute to facilitate the formation of electrons and provide good diffusion channels for the movement of electrolyte ions throughout the charge–discharge procedure.

Enhanced hydrogen adsorption-desorption reversibility found on NiAl alloy: A first-principles study

Improving the hydrogen storage performance of carbon-based materials via transition metals incorporation has been proved experimentally, where control over the hydrogen adsorption kinetics and hydrogen surface diffusion is the key. In this work, we proved theoretically via density functional theory (DFT) how such incorporation promotes better hydrogen storage performance in Ni-based materials supported on graphene, in which static and dynamic behavior of the system were modeled by plane-wave DFT and ab initio molecular dynamics (AIMD), respectively. In addition, the hydrogen storage materials Ni10Al3 and Ni13 supported on graphene, denoted as Ni10Al3/GP and Ni13/GP, are modeled to realize the experimental observation on Ni3Al alloy under high hydrogen pressure. It was found that the Ni10Al3/GP alloy system exhibited better properties in twofold: (1) increased hydrogen adsorption capacity through providing an additional site for H2 molecular adsorption, particularly on the Al atoms, and (2) enhanced hydrogen desorption at ambient conditions observed from reversible H2 adsorption at all coverages with barrierless migration energy. Therefore, the proof from the DFT point-of-view provides valuable insight into exploring other metal alloy systems that can provide additional sites for molecular hydrogen adsorption and improve hydrogen adsorbate mobility.

Novel spinel based high entropy oxide as electrode for symmetric SOFCs

Fabrication of symmetric electrodes for intermediate temperature SOFCs can significantly reduce fuel cell production costs without compromising efficiency. Herein, we report a novel spinel based high entropy oxide (CuLiFeCoNi)1.4Mn1.6O4-δ (CM-HEO) that exhibit better symmetric electrode properties than the parent spinel oxide, Cu1.4Mn1.6O4-δ (CM). The prepared HEO exhibited good structural and thermal stability up to 800 °C as inferred from the XRD, Raman and TGA-DSC results. Temperature-programmed reduction and desorption profiles of CM-HEO outperformed CM by exhibiting hydrogen adsorption and lower CO2 desorption across different temperature ranges. The enhancement of Lewis acid-base sites is evident from the XPS analysis validating the observed increase in HOR and ORR activity. The high electrocatalytic activity of the material arise from its lower activation energies (0.27 eV in air, 0.09 eV in dry H2 and 0.03 eV in dry CH4) with a polarisation resistances of 0.152 Ωcm2 under ambient atmosphere and 0.044 Ωcm2 under dry H2. These findings exalt CM-HEO as an efficient symmetric SOFC electrode material.

Phonon transport characteristics of α, β, and γ crystalline phases of magnesium hydride from first-principles-based anharmonic lattice dynamics

The superior gravimetric and volumetric hydrogen capacities of magnesium hydride (MgH2) make it a promising candidate material for solid-state hydrogen storage. However, the slow kinetics of hydrogen atoms and the high thermodynamic stability of MgH2 hinder its practical application. To address the challenging issue of adsorption–desorption in MgH2, structural engineering involving nanostructuring has been used to improve the hydrogen-storage characteristics of this material. However, although structural engineering and thermal management significantly influence material properties, no microscopic understanding of the heat conduction property of pristine MgH2 exists. Further advances in the thermal engineering of MgH2-based hydrogen-storage materials require a better understanding of heat conduction in pristine MgH2, particularly knowledge of how the crystalline phases of MgH2 depend on the hydrogen concentration and external pressure. This study uses first-principles-based anharmonic lattice dynamics to quantitatively investigate the intrinsic thermal conductivity of heat-carrying phonons in pristine MgH2 with three different crystalline phases α, β, and γ. The results show that the thermal conductivity of MgH2 depends on the crystalline phase and that the magnitude of the thermal conductivity increases in the order α, γ, and β. In contrast, the volumetric heat capacity and mean squared displacements of the constituent atoms are similar for all three phases. Furthermore, as observed for the pressure dependence of phonon transport, increasing the pressure reduces the thermal conductivity of all phases. However, for the γ and β phases, these reductions are relatively moderate because of the competing effects of group velocity and relaxation time, which have opposite dependencies on pressure. Finally, modal analysis indicates that the spectral features of the phonon transport properties under an applied external pressure are comparable to those at atmospheric pressure. These results should help tailor the heat dissipation of MgH2 while maintaining its hydrogen adsorption–desorption performance through structural engineering.

Ruthenium-doped cobalt sulphide electrocatalyst derived from a ruthenium-cobalt Prussian blue analogue (RuCo-PBA) for an enhanced hydrogen evolution reaction (HER).

The designing of efficient electrocatalysts for hydrogen generation is essential for the practical application of water-splitting devices. With numerous electrochemical advantages, transition metal sulphides are regarded as the most promising candidates for catalysing the hydrogen evolution reaction (HER) in acidic media. In the present study, Ru-doped cobalt sulphide nanosheets, termed Co9S8/Ru@t (t = 24 h, 48 h, and 72 h), were obtained by varying the reaction time from 24 h to 72 h from a RuCo-PBA precursor. The role of the time period for the synthesis of Co9S8/Ru@48h is vital in increasing the number of electroactive sites and optimising the hydrogen adsorption-desorption phenomena leading to an increment in the HER activity. The electrochemical outcomes demonstrate that the optimized Co9S8/Ru@48h requires a low overpotential of just 94 mV to produce 10 mA cm-2 current density, and also exhibits a lower Tafel slope value of 84 mV dec-1 defining its faster reaction kinetics. The as-synthesized Co9S8/Ru@48h was stable for up to 20 h of constant electrolysis signifying its outstanding durability. The optimized synthetic approach and impressive electrochemical results make Co9S8/Ru@48h a suitable alternative to noble-metal-based electrocatalysts for the HER.

Reversible hydrogen storage in Li-functionalized [1,1,1,1]paracyclophane: A computational insight

This study focuses on investigating the hydrogen adsorption-desorption properties and storage capacities of Li functionalized [1,1,1,1]paracyclophane (PCP1111) using dispersion-corrected density functional theory and molecular dynamics simulation. The Li atom is bound to the [1,1,1,1]paracyclophane's benzene ring via Dewar mechanism, with a binding energy of 0.32 eV without any clustering. Each Li atom is found to adsorb 5H2 molecules, causing the host material PCP1111–4Li to adsorb up to 20H2 molecules via charge polarization with an average adsorption energy of 0.156 eV/H2, indicating physisorption type adsorption. The charge polarization during hydrogen adsorption is studied using Hirshfeld charge analysis and electrostatic potential maps. PCP1111–4Li saturated with 20H2 results in gravimetric densities as high as 9.4 wt%, which is considerably higher than the US-DOE target. During the H2 adsorption process, the host material's geometry does not change significantly, indicating its chemical stability. When the temperature exceeds 180 K under 30–60 bar, the gravimetric density decreases, but it is still greater than 5.5 wt%, which is the target set by the US Department of Energy for 2025. The maximum H2desorption temperature estimated by the Vant-Hoff relation is found to be 216 K and 266 K at 1 atm and 5 atm, respectively. ADMP molecular dynamics shows the structural integrity and reversibility of host materials.

Synergistic hydrogen generation through a 2D-2D NiCuInS2:In2S3/g-C3N4 dual S-scheme heterojunction nanosheets

In this study, we report on the synthesis and characterization of 2D-2D nanosheets of NiCuInS2: In2S3/g-C3N4 (NCIS/CN) as a highly efficient photocatalyst for hydrogen production. Under visible light irradiation, the NCIS/CN heterojunction exhibited a remarkable hydrogen production rate of 2.5 mmol/h/g, which is 133-fold higher than the pristine CN and NCIS. This exceptional performance was attributed to the synergetic effects of Ni–Cu–In trimetallic active sites for hydrogen adsorption-desorption and dual S-scheme heterojunction, which facilitated charge separation and transfer. The heterojunction was characterized by various spectroscopic and microscopic techniques, which revealed the presence of staggered band alignment and a double internal electric field. These results demonstrate the potential of 2D-2D heterojunctions for the development of highly efficient photocatalysts for renewable energy production and pave the way for the design of new and innovative heterojunctions for various photocatalytic applications.

Thermodynamic and kinetic isotope effects on hydrogen absorption by Pd–Al2O3 pellets

Palladium has been widely served as the separation material in the hydrogen isotope separation process on account of its unique hydrogenation characteristics. To reduce Pd pulverization effect and improve the gas flow rate, Pd–Al2O3 (Pd deposited on Al2O3) is commonly used as the separation material. It is crucial to grasp the hydrogen absorption and desorption thermodynamics and kinetic isotope effect of Pd–Al2O3 material, which favours raising the separation efficiency. In this work, the effect of PdO existing in the fresh Pd–Al2O3 on the thermodynamic character of Pd–Al2O3–H(D) system and the porous substrate effect on the hydrogen absorption kinetics of Pd–Al2O3 were investigated. It shows that PdO could totally reduce to Pd after primary hydrogen adsorption-desorption, leading to decreased hydrogen absorption capacity. However, it has no effect on the enthalpy and entropy values of Pd–Al2O3–H (D) system. The kinetic analysis of hydrogen adsorption of Pd–Al2O3 shows that the hydrogen absorption of Pd–Al2O3 could be fitted by Mample model, a special case of the JMAK model, and the interface-controlled model can be deduced. The porous substrate influences the rate of hydrogen adsorption of Pd–Al2O3. The SEM and XRD results show that after 60 hydrogen absorption-desorption cycles, the surface of Pd–Al2O3 pellet has a slight change with a pulverization rate of 3.3 wt%, although the high-strength alumina support can withstand the stress caused by Pd expansion during hydrogen absorption.

Ni(OH)2 Derived from NiS2 Induced by Reflux Playing Three Roles for Hydrogen/Oxygen Evolution Reaction

Developing efficient and promising non-noble catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital but still a huge challenge for the clean energy system. Herein, we have integrated the active components for OER (Ni(OH)2) and HER (NiS2 and Ni(OH)2) into Ni(OH)2@NiS2 heterostructures by a facile reflux method. The in-situ formed Ni(OH)2 thin layer is coated on the surface of hollow NiS2 nanosphere. The uniform Ni(OH)2@NiS2 hollow sphere processes enlarge the electrochemically active specific surface area and enhance the intrinsic activity compared to NiS2 precursor, which affords a current density of 10 mA cm−2 at the overpotential of 309 mV and 100 mA cm−2 at 359 mV for OER. Meanwhile, Ni(OH)2@NiS2 can reach 10 mA cm−2 at 233 mV for HER, superior to pure NiS2. The enhanced performance can be attributed to the synergy between Ni(OH)2 and NiS2. Specifically, Ni(OH)2 has three functions for water splitting: providing active sites for hydrogen adsorption and hydroxyl group desorption and working as real OER active sites. Moreover, Ni(OH)2@NiS2 displays great stability for OER (50 h) and HER (30 h).

In-plane heterostructured MoN/Mo2N nanosheets as high-efficiency electrocatalysts for alkaline hydrogen evolution reaction

Economical and efficient electrocatalysts are crucial to the hydrogen evolution reaction (HER) in water splitting to produce hydrogen. Heterostructured electrocatalysts generally exhibit enhanced HER catalytic activity due to the strong electron coupling effects and synergistic optimization of hydrogen adsorption–desorption. Herein, in-plane heterostructured MoN/Mo2N nanosheets are fabricated as high-efficiency HER electrocatalysts in the alkaline medium from bulk MoS2 by molten salt-assisted synthesis. Density-functional theory calculations and experiments show that the in-plane heterostructured MoN/Mo2N nanosheets facilitate interfacial electron redistribution from Mo2N to MoN, giving rise to more negative H2O adsorption energy and optimal hydrogen adsorption free energy (ΔGH* = −0.017 eV). Consequently, a low overpotential of 126 mV at 10 mA cm−2 and a small Tafel slope of 69.5 mV dec−1 are achieved in the 1M KOH electrolyte, demonstrating excellent HER characteristics. Moreover, the overpotential shows negligible change after operating at 50 mA cm−2 for 12 h, confirming the excellent stability. The results reveal a novel and effective strategy to design highly efficient 2D in-plane heterostructured HER electrocatalysts for water splitting.

Synthesis, characterization, and electrochemical evaluation of SnFe2O4@MWCNTS nanocomposite as a potential hydrogen storage material

The widespread use of hydrogen as a vehicle fuel has prompted us to develop a new nanocomposite by immobilizing of tin ferrite nanoparticles (SnFe2O4) on the surface of multi-walled carbon nanotubes (abbreviated as MWCNTS) for the first time. The prepared nanocomposite powder (SnFe2O4@MWCNTS) was investigated utilizing various microscopy and spectroscopy methods, such as FT-IR, XRD, SEM, EDX, and BET techniques. Moreover, the electrochemical property of SnFe2O4@MWCNTS nanocomposite was investigated by cyclic voltammogram (CV) and charge–discharge chronopotentiometry (CHP) techniques. A variety of factors on the hydrogen storage capacity, such as current density, surface area of the copper foam, and the influence of repeated hydrogen adsorption-desorption cycles were assessed. The electrochemical results indicated that the SnFe2O4@MWCNTS has high capability and excellent reversibility compared to SnFe2O4 nanoparticles (NPs) for hydrogen storage. The highest hydrogen discharge capability of SnFe2O4@MWCNTs was achieved ∼ 365 mAh/g during the 1st cycle, and the storage capacity enhanced to ∼ 2350 mAh/g at the end of 20 cycles using a current of 2 mA. Consequently, the SnFe2O4@MWCNTS illustrated great capacity as a prospective active material for hydrogen storage systems.