Electrode For Hydrogen Evolution Reaction Research Articles

Hydrogen Evolution Reaction of BaSnO3- δ Thin Film on p-Si

Oxide perovskites are proposed as photoelectrodes for the hydrogen evolution reaction(HER) in alkaline solutions. The cubic perovskite BaSnO3 can be used as a photoelectrode due to the edge position of conduction band, which is lower than the reduction potential. However, since it has a wide band gap of 3.1 eV, it is limited to use energy of a long wavelength including visible light. In this research, we investigated photoelectrochemical characteristics of BaSnO3 thin film deposited by Pulsed laser deposition(PLD) with promoting oxygen vacancy. The HER performance was enhanced due to band gap adjusted oxygen vacancy concentration. Furthermore, Electrochemical Impedance Spectroscopy(EIS) was measured to confirm surface charge resistance and charge transport. Thus, this study introduces that BaSnO3-δ/p-Si can be an efficient electrode for HER.

Amorphous nickel sulfoselenide for efficient electrochemical urea-assisted hydrogen production in alkaline media

Abstract Amorphous Ni sulfoselenide on the surface of Ni(OH)2 nanoplate that is supported by nickel foam is synthesized, which demonstrates high activity and durability for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) in alkaline media. As for HER, the introduction of sulfur in Ni sulfoselenide not only increases the electrochemical active area, but also improves the water adsorption ability and provides an optimal adsorption site for hydrogen atom. As for UOR, the in-situ formed amorphous oxyhydroxide is believed as the real active species. The electrolyzer assembled by Ni sulfoselenide electrodes shows a low voltage of 1.47 at 10 mA cm−2 in 1 M KOH + 0.5 M urea, which is much lower than that required for overall water splitting. The present work demonstrates an effective bifunctional electrode for HER and UOR that can be used to produce hydrogen and remove pollutant (urea) in water at the same time.

Heteroatom Modification of Nanoporous Nickel Surfaces for Electrocatalytic Water Splitting

Herein, we report heteroatom (N and O)-modified nanoporous Ni surfaces on Ni foam (NF) as a high-performance bifunctional electrode for hydrogen evolution reaction (HER) and oxygen evolution reacti...

3D flexible WxV1-xSe2 nanoplates arrays on carbon cloth as an novel efficient hydrogen evolution electrocatalysts

Developing a highly stable electrocatalysts for hydrogen generation is gaining considerable attention for sustainable development of energy storage and conversion. In this paper, vertically aligned tungsten (W) doped vanadium diselenide (VSe2) nanoplates array is successfully synthesized on carbon cloth (CC) to form 3-dimensional (3D) electrode for hydrogen evolution reaction (HER) reaction. The optimal WxV1-xSe2 nanoplates array exhibit substantially low overpotentials of 173 mV to drive 10 mA cm−2 respectively, as compared with pristine VSe2 (280 mV) in acidic conditions. The Tafel slope values of WxV1-xSe2 nanoplates array is noted to be 80 mVdec-1 in acidic conditions. Furthermore, WxV1-xSe2 nanoplates array catalyst delivers significant cycling stability in acidic conditions. The significant catalytic performance is attributed to doping effect of W in VSe2, which actually enhances the conductivity and creates number of catalytic active sites to increase the electrocatalytic activity. The results highlight that WxV1-xSe2 nanoplates could be a promising candidate for electrocatalyst in water splitting applications.

Facile synthesis and electrochemical performances of three dimensional Ni3S2 as bifunctional electrode for overall water splitting

3D Ni3S2 /Ni foam electrocatalysts were successfully synthesized through a facile one-step solvothermal method in Methanol, Ethanol and Ethylene glycol solutions, then directly applied as the electrodes for hydrogen evolution reaction and the oxygen evolution reaction. The electrochemical measurements demonstrated the excellent electrochemical activity and stability toward water splitting, Moreover, the electrocatalytic behaviors of the samples were also investigated at various temperatures (0–60 °C), systematically. Remarkably, the electrolyzer based on 3D Ni3S2 /Ni foam electrodes delivered a current density of 20 mA cm−2 at a cell of voltage of 1.89 V and shows excellent long-term stability. The porous three dimensional structure of Ni3S2/NF electrodes, electrical conductivity, and large electrochemical surface area are responsible for the excellent electrocatalytic performances The study presents a feasible and effective strategy to prepare highly efficient electrocatalysts for water splitting.

Recent advances in screening two-dimensional materials for high-performance energy storage and conversion devices based on electronic structure theory

With the ever-growing global energy demands and environmental pollution issues, developing high-performance energy storage and conversion materials has become a hot topic in the material science community. In this regard, substantial progress has been made in theoretically predicting new materials for energy-related fields, experimentally synthesizing these materials, and further improving their properties for high performance in energy storage and conversion devices. In particular, two-dimensional (2D) materials have shown great potential in the field of energy storage and conversion. However, it remains challenging to explore 2D materials that render high efficiency of energy storage and conversion while guarantee long-term stability and safety. Over the past decades, theoretical calculations based on density functional theory (DFT) have become a practical toolkit to address this issue by revealing the reaction mechanism at an atomic scale and screening high-performance energy storage and conversion materials on a large scale. In particular, DFT calculations enable us to establish the relationships between the intrinsic properties of materials and their performance for energy storage and conversion, and provide theoretical guidance for screening and experimentally synthesizing the promising materials. In this review, we summarize the DFT calculations’ applications in recent studies of developing high-performance and reliable energy-related 2D materials for Li-ion battery (LIB), water splitting, fuel cells, and electrochemical carbon dioxide reduction (CRR). First, we introduce the reaction mechanism of LIB, hydrogen evolution reaction (HER), oxygen evolution reaction/oxygen reduction reaction (OER/ORR), and CRR in detail and the application of 2D material in these fields. Then, we highlight the role of DFT calculations in unveiling the intrinsic relationships between the electronic structure and the performance of 2D materials by comprehensively discussing the descriptors in predicting the performance of 2D materials. For example, the occupancy of d orbital and energy required to fill empty states serve as descriptors to predict the electrochemical performance of the electrode in ion intercalation battery. The d orbital center, lowest unoccupied states, and oxygen vacancy formation energy serve as descriptors to predict the catalytic performance of electrode in HER. The energy difference between the lowest valance electron orbital center and Fermi level, occupancy of p z orbital, and the energy difference between p z and p x /p y orbital center serve as descriptors to predict the catalytic performance of electrode in ORR. Even though these descriptors can help to further understand the relationships between the electronic structure and the performance of the electrochemical electrode, they are only reliable to specific materials and inapplicable to the electrode with a complex structure or complex reaction path, such as the electrode in CRR. Newly developed machine learning methods may bring a breakthrough to the exploration of a universal descriptor, which is a key factor in the large-scale screening of potential electrode materials with excellent performance and the dependable guidance to experimental synthesis. Finally, we summarize the disadvantage of DFT calculation, such as the underestimation of bandgap and incorrect description of van der Waals interaction, and give a perspective of DFT calculations in the study of new energy-related materials. The method to simulate the ambient environment of the electrode (including the electrolyte, external electric field, and non-cooperative transfer of proton and electron) based on DFT calculation is needed to be developed, which is vital to reflect the actual working condition of the electrode. The universal descriptor applicable to the electrode with a complex structure is also needed to explore to overcome the poor versatility of single intrinsic property of the material in predicting the performance of the electrochemical electrode.

Modification of the ultrasonication derived-g-C3N4 nanosheets/quantum dots by MoS2 nanostructures to improve electrocatalytic hydrogen evolution reaction

In this work, graphitic carbon nitride (g-C3N4) nanosheets/quantum dots (NS/QD) was prepared using a simple and low-cost procedure. By two steps exfoliation in a bath and tip sonicator, the g-C3N4 (NS/QD) was produced from bulk g-C3N4. To improve electrocatalytic hydrogen evolution reaction (HER), the g-C3N4 (NS/QD) were modified by the MoS2 nanostructures. Nanocomposite of the g-C3N4 (NS/QD) with MoS2 nanostructures was deposited on a flexible, conductive and three dimensional carbon cloth by a facile and binder-free electrophoretic technique. This electrode exhibited a Tafel slope of 88 mV/dec and an overpotential of 0.28 V vs RHE at −2 mA/cm2, lower than that of the g-C3N4, and good stability after 1000 cycles and 100 days for HER. The enhanced electrocatalytic performance was attributed to the MoS2 and g-C3N4 nanostructures on three dimensional carbon cloth, leading to high surface area and more number of the exposed active sites for HER. This heterostructure improved charge transport, proton adsorption and hydrogen evolution on the electrode. This work proposes cost-effective, stable and three dimensional g-C3N4 based electrode for hydrogen evolution reaction.

An open-structured carbon fiber brush electrode for efficient hydrogen evolution by inducing oriented bubble transport

Hydrogen, as a promising energy carrier to alleviate the global issues of energy crisis, has arisen a worldwide concern. However, the lack of management of the produced bubbles on electrode surface is one of the critical barriers for hydrogen evolution reaction (HER) since insufficient bubble removal causes the blockage of the active sites, increased ohmic resistance in the electrolyte and deficient ion transfer from the bulk solution to the electrode surface. In this study, an open-structured carbon fiber brush electrode (CFB) that can be produced by simply twisting a folded Ti wire fitted with carbon fibers was proposed. As a proof-of-concept demonstration, an earth-abundant electrocatalyst, MoS2 nanosheets was loaded on the CFB via solvothermal method to fabricate the HER electrode (MoS2⊥CFB). This structure not only ensures a uniform electrocatalyst distribution throughout the exterior and internal electrode surface but also ensures an improved exposure of active sites and a sufficient reaction ion supply by inducing oriented hydrogen bubble transport during the electrochemical process. Additionally, the open structure of CFB accelerates fluid flow around the electrode, which also guarantees a sufficient proton supply and hydrogen bubble removal. As a results, MoS2⊥CFB exhibits a 3.7 times higher current density at an overpotential of 400 mV and prominent durability as compared with the same catalyst growing on the common carbon cloth substrate.

Wood-derived electrode supporting CVD-grown ReS2 for efficient and stable hydrogen production

Rhenium disulfide (ReS2) as a catalyst is promising in water splitting for hydrogen evolution reaction (HER) owing to its unique structure and physiochemical property. Chemical vapor deposition (CVD) is one of effective means for the fabrication of high-crystallinity ReS2. At present, conductivities of typical substrates used for the CVD growth are mostly poor. The transfer to a conductive support or other engineering for improving the conductivity is necessarily required for the application of HER electrode. However, the damage to original structure and the introduction of impurities are highly possible in the process. The cost of time and material is also increased. In this work, we propose that a wood-derived carbon framework is used as a working electrode supporting CVD-grown ReS2 nanosheets in electrocatalytic HER. The optimal HER electrode with unique pore-through structure exhibits effective electrochemical surface area of 521 cmECSA2 and outstanding stability over 11 h. Such a carbon framework derived from natural wood is earth-abundant, ecofriendly and renewable, which can be potentially applied in the green energy industry.

Waste leather-derived (Cr, N)-co-doped carbon cloth coupling with Mo2C nanoparticles as a self-supported electrode for highly active hydrogen evolution reaction performances

In leather industry, it is a big challenge to deal with tons of waste leathers, especially those containing chromium. On the other hand, non-precious cost-effective hydrogen evolution reaction (HER) electrocatalysts are of considerable demands for environmentally-friendly energy production. Herein, in order to meet these two challenges, we creatively utilized chromium-containing waste leathers to fabricate high performance non-precious HER catalysts. Leather consists of collagen bundles; high temperature annealing of Cr-containing waste leather results in the formation of (Cr, N)-co-doped carbon cloth (CNCC). Molybdenum carbide nanoparticles can be simultaneously coupled onto CNCC (Mo2C@CNCC) by loading Mo oxyanions on waste leather through wet impregnation before annealing. The resulted Mo2C@CNCC is self-supported and can be directly applied as HER electrode, which exhibits outstanding electrocatalytic HER performances in alkaline media with low overpotential (113 mV at 10 mA/cm2) and long-term stability (more than 70 h). The existence of Cr in waste leather is unbeneficial for waste leather disposition, but plays an important role to enhance the HER performances. This simple “changing harm for the treasure” route provides a new green concept for dealing with waste leather and creating high performance electrocatalysts.

Deposit amorphous Ni-Co-B-RE (RE = Ce, Gd and Nd) on nickel foam as a high performance and durable electrode for hydrogen evolution reaction

Abstract The rare earths (RE) are widely used in composites modification. In this study, the morphology, the electronic structure and the catalytic performance have been investigated by doping RE. The amorphous structure of Ni-Co-B-RE/NF (RE = Ce, Gd and Nd, NF = Ni foam) electrodes, which can be used as a catalyst for the hydrogen evolution reaction (HER), was prepared on Ni foam by a handy chemical deposition method. Interestingly, the synergistic effect of rare earth Gd and electronic materials (e.g. Ni, Co and B) can accelerate deposition rate and refine coated particles. The results suggest that the Ni-Co-B-Gd/NF electrode exhibits excellent catalytic performance in alkaline solutions, which shows a high electrochemical stability even with overpotential of 92 mV at a current density of 10 mA cm−2 and Tafel slope of 105 mV dec−1.

Electrodeposition of Ni–Fe–Mn ternary nanosheets as affordable and efficient electrocatalyst for both hydrogen and oxygen evolution reactions

The synthesis of high performance and economical electrocatalysts in the process of overall water splitting is very important for the production of hydrogen energy and has become one of the most important challenges. Here, various Ni, Ni–Fe, Ni–Mn nanosheets and Ni–Fe–Mn ternary nanosheets were created using cost-effective, versatile and binder-free electrochemical deposition methods, and the electrocatalytic activity of various electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were investigated in an alkaline environment. Due to the high electrochemical active surface area due to the fabrication of nanosheets, the synergistic effect between different elements on the electronic structure, the high wettability due to the formation of nanosheets and the quick detachment of formed gasses from the electrode, the Ni–Fe–Mn nanosheets electrode showed excellent electrocatalytic activity. In order to deliver the 10 mA cm−2 current density in HER and OER processes, this electrode required values of 64 mV and 230 mV overpotential, respectively. Also, the stability test showed that after 10 h of electrolysis at a current density of 100 mA cm−2, the overpotential changes was very small (less than 4%), indicating that the electrode was excellent electrostatic stability. Also, when using as a bi-functional electrode in the full water splitting system, it only needed a cell voltage of 1528 V to deliver a current of 10 mA cm−2. The results of this study indicate a new strategy for the synthesis of active and stable electrocatalysts.

Metal-Organic Powder Thermochemical Solid-Vapor Architectonics toward Gradient Hybrid Monolith with Combined Structure-Function Features

The conversion of inorganic powders or metal powders into gradient components is typically achieved with the help of a non-uniform electric or pressure field. However, the current technologies are ineffective in converting powder into gradient-structured hybrid components with combined structure-function features because of the lack of a non-uniform field to control evolution of the structures. The present work addresses this challenge by taking advantage of uniformly distributed metal nanoparticles and non-uniformly distributed reactive gases generated during thermopyrolysis of metal-organic powder to generate gradient metal-carbon monolith via combined chemical vapor deposition and solid-state welding. The obtained monolith shows good mechanical strength and high catalytic activity, allowing it to be used as a working electrode for a seawater battery. This method connecting gas-solid-state synthesis together with processing may lead to other gradient hybrid monoliths in the future.A gradient carbon-metal hybrid component can be manufactured by thermopyrolysis of metal-organic framework powder. The non-uniformly distributed carbonaceous vapor and uniformly dispersed Co nanoparticles are essential for generating the gradient carbon monolith. This monolith exhibits good mechanical strength and high catalytic activity, and thus can be directly utilized as an electrode for a Mg/HO battery to generate electricity from seawater. The assembled battery shows power density comparable with that of a battery with Pt as the electrode.Direct manufacturing from powder to final component is of great significance for industry. However, it remains a challenge to develop a one-pot “powder-to-product” strategy to produce gradient hybrid components with combined structural and functional advantages. In this work, we report metal-organic powder thermochemical solid-vapor architectonics to direct zeolitic imidazolate framework powder into gradient cobalt/carbon monolith by utilizing in situ generated reactive vapor (non-uniform distribution) and Co nanoparticles (uniformly distributed) to achieve a combination of chemical vapor deposition/growth and solid-state welding. The gradient hybrid monolith possesses good mechanical stability, allowing it to be directly used as a freestanding working electrode for hydrogen evolution reaction in a seawater battery. This catalyst shows a low overpotential of 84 mV at a current density of 10 mA cm. Furthermore, a stable power generation of over 168 h in seawater has also been realized.

Electroplated synthesis of semi-rigid MoS2–rGO–Cu as efficient self-supporting electrode for hydrogen evolution reaction

The self-supporting catalytic electrode is useful in the industry, since it can reduce the complex pre-treatment of catalytic materials and avoid the use of binders. In this work, a ternary self-supporting electrode including Cu mesh-supported graphene and molybdenum disulfide (MoS2) was prepared by electroplating zinc and hydrothermal reaction. Due to the excellent conductivity of copper and the hydrogen evolution catalytic ability of MoS2, this self-supporting electrode showed a low Tafel slope as 54 mV dec−1 and a current density of 400 mA cm−2 at an overpotential of -300 mV in hydrogen evolution reaction (HER). In addition, due to the metal flexibility of the Cu mesh substrate, the MoS2–rGOCu ternary self-supporting electrode can be bent or cut into any desired shape. Even shaped as an elongated one, curved "S", this self-supporting electrode still kept itself from any deformation when hydrogen bubbles were rapidly generated. Therefore, a strategy for green, simple, and low-cost self-supporting electrode was provided, which may increase the large-scale operation of the catalytic electrode in HER.

Bacterial nanocellulose as a green and flexible electrode matrix for efficient hydrogen evolution reaction in alkaline conditions

Bacterial nanocellullose (BNC) is a versatile matrix for designing and incorporating three-dimensional functional nanomaterials for different applications. The present study describes the fabrication of a flexible catalytic electrode for hydrogen evolution reaction using nanocellulose derived from Komagataeibacter sucrofermentans. By simple electroless deposition, the BNC is transformed into a conductive flexible substrate. On the subsequent electrodeposition process in a solution of Ni and Mo, the conductive BNC made into an active electrode for hydrogen (H2) generation. The highly nano-porous architecture and binder-free nature of the BNC electrode enhances the surface active sites and exhibit an excellent catalytic hydrogen production in alkaline conditions. Electrochemical studies show that the NiMoO4/BNC electrode to achieve a current density of 10 mA cm−2 requires an overpotential of 109 mV with a Tafel slope of 170 mV dec−1 in 1 M KOH. Moreover, the electrode demonstrates good stability in the alkaline medium during prolonged electrolysis for 48 h. The study offers the fabrication of BNC based electrode for efficient electrocatalytic hydrogen production and promoting the usage of green materials in renewable energy technologies.

Self-Supported Vanadium Carbide by an Electropolymerization-Assisted Method for Efficient Hydrogen Production.

Exploring efficient electrodes toward the hydrogen evolution reaction (HER) remains a great challenge for large-scale hydrogen production. Owing to its high earth abundance, low electrical resistivity, and small density, vanadium carbide (VC) is a promising HER electrode candidate but has been rarely explored. In this work, VC nanoparticles encased in nitrogen-doped carbon matrix on carbon cloth (VC@NC/CC) were prepared as a binder-free HER cathode through electropolymerization followed by carbothermal reduction under argon. In the first step of pyrrole electropolymerization, the VO4 3- anions, serving as both vanadium source and supporting electrolyte, were homogeneously incorporated in the positively charged polypyrrole (PPy) framework through coulombic interaction. The electropolymerization was effective for preparation of binder-free metal carbide materials with various polymer monomers as carbon source, which was favorable for the high performance of metal carbide electrodes. During the pyrolysis process, the polymeric hybrids were converted to VC nanoparticles and entrapped in the PPy-derived N-doped carbon matrix. The optimized VC@NC/CC electrode exhibited high catalytic activity and durability in both acidic and alkaline media. The use of VC for efficient HER is remarkable, and such a convenient and versatile electropolymerization-assisted method is appealing for the fabrication of industrially scalable large-area VC electrodes for efficient hydrogen production.

Ultrathin VS2 nanosheets vertically aligned on NiCo2S4@C3N4 hybrid for asymmetric supercapacitor and alkaline hydrogen evolution reaction

Hollow transition metal sulfide hybrid nanostructures offer promising potential materials for electrochemical water splitting and energy storage applications. Herein, we demonstrate the rational design of hollow structured NiCo2S4@C3N4@VS2 hybrid nanostructures for asymmetric supercapacitor and alkaline hydrogen evolution reaction (HER). Through an efficient step-by-step strategy, ultrathin VS2 nanosheets were vertically grown on C3N4 coated NiCo2S4 hollow nanospheres to form NiCo2S4@C3N4@VS2 hybrid nanostructures. Benefiting from intriguing morphological features and conductivity, NiCo2S4@C3N4@VS2 hybrid nanostructures exhibit a large specific capacitance 1984.1 F/g at 1 A/g, superior rate capacity (91.5% at 5 A/g) and outstanding durability (retaining 88.4% over 5000 cycles at 5 A/g). Moreover, the NiCo2S4@C3N4@VS2//AC asymmetric supercapacitor device provides a large energy density (31.7 Wh/kg), remarkable power density (711.1 W/kg) and superior cycle life (retention of 91.2% after 5000 cycles). Furthermore, the hybrid nanostructures manifest enhanced electrochemical activity as electrocatalysts for HER process with small Tafel slope of 71.8 mV dec−1, excellent overpotential of 110 mV at 10 mA cm−2 and remarkable stability. Thus, the NiCo2S4@C3N4@VS2 hybrid nanostructures can hold excellent potential for advanced asymmetric supercapacitor and alkaline HER electrodes.

Amorphous MoS2 nanosheets on MoO2 films/Mo foil as free-standing electrode for synergetic electrocatalytic hydrogen evolution reaction

A facile oxidation-sulfidation strategy is proposed to fabricate the vertically aligned amorphous MoS2 nanosheets on MoO2 films/Mo foil (MF) as free-standing electrode, which features as the integration of three merits (high conductivity, abundant exposures of active sites, and enhanced mass transfer) into one electrode for hydrogen evolution reaction (HER). Density functional theory (DFT) calculations reveal the strong interaction between MoS2 and MoO2, which can enhance the intrinsic conductivity with narrow bandgap, and decreases hydrogen adsorption free energy (ΔGH∗ = ~0.06 eV) to facilitate the HER process. Benefiting from the unique hierarchical structure with amorphous MoS2 nanosheets on conductive MoO2 films/MF to facilitate the electron/mass transfer by eliminate contact resistance, controllable number of stacking layers and size of MoS2 slabs to expose more edge sites, the optimal MoS2/MoO2/MF exhibits outstanding activity with overpotential of 154 mV at the current density of 10 mA cm−2, Tafel slope of 52.1 mV dec−1, and robust stability. Furthermore, the intrinsic HER activity (vs. ECSA) on MoS2/MoO2/MF is significantly enhanced, which shows 4.5 and 18.6 times higher than those of MoS2/MF and MoO2/MF at overpotential of 200 mV, respectively.

Hydrogen Evolution Reaction by Atomic Layer-Deposited MoNx on Porous Carbon Substrates: The Effects of Porosity and Annealing on Catalyst Activity and Stability.

Molybdenum-based compounds are considered as a potential replacement for expensive precious-metal electrocatalysts for the hydrogen evolution reaction (HER) in acid electrolytes. However, coating of thin films of molybdenum nitride or carbide on a large-area self-standing substrate with high precision is still challenging. Here, MoNx is uniformly coated on carbon cloth (CC) and nitrogen-doped carbon (NC)-modified CC (NCCC) substrates by atomic layer deposition (ALD). The as-deposited film has a nanocrystalline character close to amorphous and a composition of approximately Mo2 N with significant oxygen contamination, mainly at the surface. Among the as-prepared ALD-MoNx electrodes, the MoNx /NCCC has the highest HER activity (overpotential η≈236 mV to achieve 10 mA cm-2 ) owing to the high surface area and porosity of the NCCC substrate. However, the durability of the electrode is poor, owing to the poor adhesion of NC powder on CC. Annealing MoNx /NCCC in H2 atmosphere at 400 °C improves both the activity and durability of the electrode without significant change in the phase or porosity. Annealing at an elevated temperature of 600 °C results in formation of a Mo2 C phase that further enhances the activity (η≈196 mV to achieve 10 mA cm-2 ), although there is a huge reduction in the porosity of the electrode as a consequence of the annealing. The structure of the electrode is also systematically investigated by electrochemical impedance spectroscopy (EIS). A deviation in the conventional Warburg impedance is observed in EIS of the NCCC-based electrode and is ascribed to the change in the H+ ion diffusion characteristics, owing to the geometry of the pores. The change in porous nature with annealing and the loss in porosity are reflected in the EIS of H+ ion diffusion observed at high-frequency. The current work establishes a better understanding of the importance of various parameters for a highly active HER electrode and will help the development of a commercial electrode for HER using the ALD technique.

Metal-Organic Powder Thermochemical Solid-Vapor Architectonics Towards Gradient Hybrid Monolith with Combined Structure-Function Features

Direct manufacturing from powder to final component is of great significance for industry. However, it remains a challenge to develop a one-pot “powder to product” strategy to produce gradient hybrid component with combined structure-function advantages. In this work, we report a metal-organic powder thermochemical solid-vapor architectonics to direct zeolitic imidazolate framework powder into gradient cobalt/carbon monolith with atomically doped nitrogen, encapsulated cobalt nanoparticles, nanotubes arrays, and well-interconnected grains. The in situ generated H 2 vapor (non-uniform distribution) and Co nanoparticles (uniformly distributed) combines a chemical vapor deposition/growth and a solids-state welding together, leading to formation of the unique gradient monolith. The gradient carbon monolith is of good mechanical stability, therefore is directly used as a freestanding working electrode for hydrogen evolution reaction (HER) in a seawater battery. This catalyst shows a low overpotential of 84 mV at a current density of 10 mA cm-2 as well as good stability for HER at a constant overpotential of 200 mV for 5 h. Furthermore, a stable power generation of over 168 h in seawater has been realized.