Hydrogen Precipitation Research Articles

Synthesis and Catalytic Performance of Mo2C/MoS2 Composite Heterojunction Catalysts.

Hydrogen, as a clean, safe, and efficient energy carrier, is one of the hot energy sources that have attracted much attention. Mo2C, due to the introduction of C atoms, makes the atomic spacing of the Mo lattice decrease and changes the width of the d-band, which makes the electronic properties of Mo2C similar to that of Pt noble metals, exhibiting excellent electrochemical hydrogen precipitation performance. MoS2, due to its special crystal structure and tunable electronic structure, has been widely studied. In this paper, Mo2C nanoparticles were prepared by high-temperature carbonization, and then two-dimensional layered MoS2 were be loaded on Mo2C nanoparticles by the hydrothermal method to synthesize Mo2C/MoS2 composite catalysts. Their electrochemical hydrogen precipitation (HER) performance under acidic conditions was tested. The above catalysts were also characterized by modern material testing methods such as XRD, SEM, TEM, and XPS. The results showed that the composite catalysts exhibited the most excellent electrochemical hydrogen precipitation performance at Mo2C/MoS2-3, with the lowest overpotential at a current density of 10 mA cm-2, Tafel slope, and electrochemical impedance. At the same time, the electrochemically active area was dramatically enhanced, with good stability under prolonged testing. The catalytic activity was significantly improved compared with that of Mo2C and MoS2. The characterization and experimental results indicate that the heterogeneous structure of Mo2C and MoS2 formed a built-in electric field between the two, which accelerated the electron transfer efficiency and provided more active sites. The Mo2C/MoS2 composite catalyst is a low-cost, easy-to-prepare, and high-efficiency electrochemical hydrogen precipitation catalyst, providing a new idea for developing green and clean energy.

Exploration of transition metal atom-doped NiSe2 electrocatalysts for efficient alkaline hydrogen precipitation using first principles screening

Transition metal (TM) doping exhibits great potential in designing high-performance two-dimensional (2D) NiSe2-based catalysts for electrocatalytic hydrogen evolution reaction (HER). 22 TM atom-doped 2D-NiSe2 catalysts are screened, and the effects of TM doping on the thermal stability and HER catalytic activity are investigated by first-principles calculations. Among them, Cu doped 2D-NiSe2 might exhibit remarkable HER properties with the water dissociation energy of 1.03 eV and H adsorption Gibbs free energy of −0.05 eV. Furthermore, we elucidate the reasons behind the different HER activities. These findings suggest new possibilities for the application of Cu doped 2D-NiSe2 for alkaline HER, offering new perspectives for future research.

Nanoporous NiPt alloy by dealloying of amorphous NiZrPt metallic glass for alkaline hydrogen evolution reaction

The development of high-performance and low-cost alkaline hydrogen precipitation catalysts is critical for the large-scale application of hydrogen energy. In this work, the nanoporous alloy catalysts were synthesized by dealloying melt-spun NiZrPt ribbons. The optimal sample after dealloying shows excellent HER performance in alkaline medium, with a small overpotential of 15 mV to deliver 10 mA cm−2 and a low Tafel slope of 20 mV/dec. The material characterization reveals that the incorporation of Ni modulates the electronic structure of Pt. After selective dealloying of Zr and Ni, a Pt-enriched nanoporous structure was formed on the catalyst surface. Meanwhile, the remaining Ni sites acted as synergistic sites to activate the Pt sites, which allowed for better hydrogen adsorption energy and faster kinetics of the catalytic reaction. Besides, the favorable mechanical flexibility of the material makes it potential for self-supporting electrode. This work presents a way to prepare low-Pt efficient catalysts by amorphous alloy dealloying.

Maltodextrin as a Commercial-Grade Electrolyte Additive Against Dendrite Formation and Side Reactions for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) directly using zinc metal anodes are promising candidates for grid-scale energy storage systems due to their intrinsic high theoretical capacity, high safety, and environmental friendliness. However, the uncontrolled dendrite growth and water-triggered side reactions seriously plague its practical application. Herein, a cost-effective and green additive, maltodextrin (MD) is presented, to simultaneously guide the smooth Zn deposition and inhibit the occurrence of water-related side reactions. Combing experimental characterizations and theoretical calculations shows that the MD molecules could reconstruct the Helmholtz plane, induces a preferential growth of zinc along the (002) plane, and the optimized regulation of the Zn2+ diffusion path and deposition location also results in the formation of fine-grained Zn deposition layers, thereby inhibiting dendrite growth. In addition, MD molecules readily adsorb to the zinc anode surface, which isolates water molecules from direct contact with the zinc metal, reducing hydrogen precipitation reactions and inhibiting the formation of by-products. Consequently, the Zn||Zn symmetric cell with MD achieves ultra-long stable cycles of up to 5430h at 1mA cm-2 and 1mA h cm-2, and the Cu||Zn asymmetric cell can stable cycle 1000 cycles with an average coulomb efficiency of 99.78%.

Preparation and Study of Ti3C2Tx MXene–Deficient In Situ Anchored Fe−Co Alloy Nanoparticle Electrocatalyst for Hydrolysis and Hydrogenolysis

AbstractThe novel two–dimensional MXene material Ti3C2Tx has the advantages of a large specific surface area, adjustable band gap, good electrical conductivity, and high stability. However, the precipitation of hydrogen via electrolytic water splitting over Ti3C2Tx has unacceptably slow kinetics. In this paper, Co nanoparticles were incorporated on the Ti3C2TxMXene surface via electrostatic adsorption by utilizing the intrinsic MXene defects generated during the etching process. Next, a Fe−Co alloy structure was also constructed on the Ti3C2TxMXenesurface by wet chemical impregnation method using the principle of galvanic coupling substitution. The prepared catalyst had an overpotential of 118 mV at a current density of 10 mA‐cm−2 and a Tafel slope of 97.56 mV dec−1. The Fe−Co alloy structure accelerated the kinetic hydrogen precipitation step, and Fe−Co/Ti3C2Txshowed excellent stability when used in a water electrolysis process for 11 h. This work offers a promising strategy for the synthesis of intrinsically defective synthetic alloy MXene structures.

Construction of Au/ZnWO4/CdS Ternary Photocatalysts with Oxygen Vacancy Modification for Efficient Photocatalytic Hydrogen Production

AbstractRational design and optimization of the photocatalyst architecture, aimed at effectively enhancing light absorption and accelerating charge separation and transfer, can lead to the accomplishment of sustainable photocatalytic hydrogen production. In this study, a ternary system of Au/ZnWO4/CdS is prepared with oxygen vacancy modification through a combination of hydrothermal, chemical precipitation, and photochemical deposition methods. The addition of CdS and Au nanoparticles significantly enhances the light absorption range of ZnWO4 (ZWO) and creates more active sites for hydrogen production. The type‐II engineered heterojunction, in combination with Au as a cocatalyst, is a viable and efficient method for enhancing the separation and transport of electron–hole pairs, thereby facilitating the effective precipitation of hydrogen through photocatalysis. 5A10ZC exhibits a hydrogen production rate of 5483.62 µmol g−1 h−1, which is 167 times higher than that of unmodified ZWO and 29 times higher than that of pure CdS. In addition, it exhibits excellent cycle stability in the hydrogen production cycle stability test. The photoelectrochemical test results show that the construction of the system improves the separation and transfer efficiency of photogenerated carriers. This study provides a new inspiration for the construction of high‐performance photocatalytic materials.

Effect of Corrosion Inhibitor Pyrovanadate Ions on Microstructure and Corrosion Resistance of MgAl Layered Double Hydroxide Films on LA43M Mg-Li Alloy

In order to explore the effect of corrosion inhibitor modification on the microstructure and corrosion resistance of MgAl layered double hydroxide (LDH) film on LA43M Mg-Li alloy, the LDH films were successfully obtained by ion exchange method at different hydrothermal temperatures. Microstructure of the MgAl LDH films with anion intercalation were characterized by SEM, EDS and XRD, and the corrosion resistance of the films were tested by EIS, polarization curve and hydrogen evolution experiments. The results showed that the modified LDH nanosheets are larger in size, denser and slightly thicker than that of MgAl LDH film. Electrochemical tests and hydrogen precipitation experiments demonstrated that the corrosion inhibitor modified LDH films can further enhance the corrosion resistance of the film. The LDH prepared at 60°C has the most uniform density and the maximum thickness. It has the lowest Icorr(1.754×10−8 A.cm2) and the most positive Ecorr(−1.147 V). Furthermore, it showed the best corrosion resistance in 3.5 wt% NaCl solution.

Limiting Interfacial Free Water and Proton Concentration by Hydrogel Electrolytes for Stable MoO3 Anode in a Proton Battery.

Aqueous rechargeable proton batteries are attractive due to the small ionic radius, light mass, and ultrafast diffusion kinetics of proton as charge carriers. However, the commonly used acidic electrolyte is usually very corrosive to the electrode material, which seriously affects the cycle life of the battery. Here, it is proposed that decreasing water activity and limiting proton concentration can effectively prevent side reactions of the MoO3 anode such as corrosion and hydrogen precipitation by using a lean-water hydrogel electrolyte. The as-prepared polyacrylamide (PAAM)-poly2-acrylamide-2-methylpropanesulfonic acid (PAMPS)/MnSO4 (PPM) hydrogel electrolyte not only has abundant hydrophilic groups that can form hydrogen bonds with free water and inhibit solvent-electrode interaction, but also has fixed anions that can maintain a certain interaction with protons. The assembled MoO3||MnO2 full battery can stably cycle over 500 times for ≈350 h with an unprecedented capacity retention of 100% even at a low current density of 0.5 A g-1. This work gives a hint that limiting free water as well as proton concentration is important for the design of electrolytes or interfaces in aqueous proton batteries.

Highly efficient photocatalytic H2 evolution and degradation properties over NiO/Mn0.5Cd0.5S S-scheme photocatalyst

Well-designed and high-performance S-scheme photocatalysts for the fabrication of green hydrogen are of significant practical significance in solving the environmental and energy crises. In this study, NiO/Mn0.5Cd0.5S S-scheme heterojunctions were triumphantly prepared by electrostatic adsorption, and the formation of energy band bending and internal electric field at the interfacial contact site between NiO and Mn0.5Cd0.5S resulted in a good photogenerated carrier separation ability and enhanced hydrogen reduction performance and Rhodamine B (RhB) degradation performance. The hydrogen production rate of NiO/Mn0.5Cd0.5S S-scheme heterojunction was enhanced to three folds of the unitary Mn0.5Cd0.5S, with an apparent quantum yield (AQY) of 15.28% at 400 nm and a degradation rate of 91.5%. In addition, the NiO/Mn0.5Cd0.5S S-scheme heterojunction has enhanced and sustainable hydrogen precipitation and RhB degradation performance.

Enhanced photocatalytic hydrogen production performance of g-C3N4 with rich carbon vacancies

Hydrogen energy is globally recognized as one of the clean and renewable chemical energy sources. Development of photocatalysts that can efficiently utilize sunlight for photocatalytic hydrogen production is an urgent mission at present. In this study, g-C3N4 with abundant pore structure and carbon defects for photocatalytic hydrogen generation was prepared by heat treatment of g-C3N4 using ammonium carbonate. The results of photocatalytic hydrogen evolution experiments demonstrate that the 5NHC sample (2 g g-C3N4 was mixed with 5.0 g ammonium carbonate) exhibits the highest hydrogen precipitation rate (972.3 μmol g-1h−1), which is 4.29 times higher than that of the reference g-C3N4 (183.6 μmol g-1h−1). Moreover, the 5NHC sample shows excellent structural stability during the hydrogen production cycling experiments, confirmed by the experimental results. Cr(VI) reduction results further demonstrate excellent photocatalytic performance of 5NHC, which is 1.54 times higher than that of the reference g-C3N4. The defective energy levels induced by carbon vacancies will lead to a rapid separation of photoinduced charge pairs, which will result in boosted photocatalytic performance. This work provides an effective strategy for development of highly performance g-C3N4.

Coupling interface constructions of ZnO@ZnS@FeOOH for photocatalytic hydrogen production performance

Photocatalysis is a reliable method to solve energy crisis and generate green energy hydrogen. ZnO@ZnS (ZOS) formed heterojunction repressed carrier complexation and thus enhanced photocatalytic performance, but its low photoresponse efficiency limited its photocatalytic performance. Therefore, in this paper, ZnO@ZnS was modified with ethylene diamine tetraacetic acid (EDTA) to form ZnO@ZnS@FeOOH composites with coupling interface. The modification of EDTA could inhibite the oxidation of FeOOH during the synthesis process, and what’s more it could enhance the charge transfer at the heterojunction interface to promote the separation of electron-hole pairs and photoresponsive ability to further enhanced the hydrogen precipitation performance. The concentration of EDTA and Fe sources were regulated to investigate the photocatalytic hydrogen production capacity of the composites. The results indicated that the ternary composite ZnO@ZnS@FeOOH had the superior hydrogen evolution performance with the hydrogen evolution rate of 529.17 umol g−1 h−1, which was 2.4 times higher than that of ZOS. EDTA acts as an electron channel to enhance the inter-interfacial electron transfer capability, and the loading of FeOOH formed a heterojunction structure, which promoted carrier separation and enhanced the photoresponse. It’s the synergistic effect to enhanced the photocatalytic hydrogen production performance. This paper provided a method for the construction of ternary heterojunctions and interfacial charge transport channels.

Preparation of Fe‐Doped Ni3S2/Ni(OH)2/Ni/NSG Composites and Enhanced Water Splitting Performance

Herein, Fe‐doped Ni3S2/Ni(OH)2/Ni@NSG electrocatalysts are prepared by dealloying Ni–Al precursors followed by magnetic stirring. It is found that the hydrogen precipitation reaction (HER) of NSG‐Fe‐25 is 148 mV at a current density of 10 mA cm−2 and the oxygen evolution reaction (OER) is 274 mV at a current density of 50 mA cm−2 compared to NSG‐Fe‐5, NSG‐Fe‐45, Ni‐NN‐Fe, and Ni‐NN‐Fe@NSG. The Tafel slopes for the HER are 81.6 mV dec−1, and the Tafel slope of OER is 61.6 mV dec−1, while the Cdl value of NSG‐Fe‐25 is larger and the resistance value is smaller. Therefore, NSG‐Fe‐25 has the optimal performance. The heterostructure of Fe‐doped Ni3S2/Ni(OH)2/Ni@NSG provides abundant active sites for surface HER and OER, which enhances the electronic conductivity of the electrode. Meanwhile, long‐term constant‐current electrolysis test experiments show that NSG‐Fe has good stability in use. The present study opens a new window for the design and preparation of total hydrolysis electrocatalysts.

Overall Spontaneous Water Splitting for Calcium Bismuthate Ca(BiO2)2: Flexible-Electronic-Controlled Band Edge Position and Adsorption-Site-Modulated Bond Strength.

Eco-friendly photocatalysts for water splitting, highly efficient in oxygen/hydrogen evolution reactions, hold great promise for the storage of inexhaustible solar energy and address environmental challenges. However, current common photocatalysts rarely exhibit both H2 and O2 production performances unless some regulatory measures, such as strain engineering, are implemented. Additionally, the extensive utilization of flexible electronics remains constrained by their high Young's modulus. Herein, on the basis of density functional theory calculations, we identify a novel spontaneous oxygen-producing two-dimensional Ca(BiO2)2 material, which can efficiently regulate the electronic structures of the surface active sites, optimize the reaction pathways, reduce the reaction energy barriers, and boost the overall water-splitting activity through biaxial strain modulation. In detail, an unstrained Ca(BiO2)2 monolayer not only possesses a suitable band gap value (2.02 eV) to fulfill the photocatalytic water-splitting band edge relationships but also holds favorable transport properties, excellent optical absorption across the visible light spectrum, and spontaneous oxygen production under neutral conditions. More excitingly, under application of a 7% biaxial tensile strain modulation with an ideal biaxial strength of 32.35 GPa nm, the Ca(BiO2)2 monolayer not only maintains its structural integrity but also exhibits a completely spontaneous reaction for photocatalytic hydrogen precipitation with superior optical absorption. This can primarily be attributed to the substantial reduction of the potential barrier through strain engineering as well as the weakening of bond energy resulting from changes of the adsorption site as calculated by crystal orbital Hamiltonian population analysis. This flexible stretchable electronic modulated the photocatalyst behavior and bond energy of O-Bi and O-Ca interactions, offering outstanding potential for photocatalytic water spontaneous oxygen and hydrogen evolution among all of the reported metal oxides, and is more likely to become a promising candidate for future flexible electronic devices.

Efficient reduction of CO2 and inhibition of hydrogen precipitation by polyoxometalate photocatalyst modified with the metal Mn.

Photocatalytic reduction of CO2 to chemical fuels is attractive for solving both the greenhouse effect and the energy crisis, but the key challenge is to design and synthesize photocatalysts with remarkable performance under visible light irradiation. Efficient catalytic carbon dioxide reduction (CO2RR) with light is considered a promising sustainable and clean approach to solve environmental problems. Herein, we found a new photocatalyst ([Mn(en)2]6[V12B18O54(OH)6]) (abbreviated as Mn6V12) based on the modifiability of polyoxometalates, in which Mn acts as a modifying unit to efficiently reduce CO2 to CO and effectively inhibit the hydrogen precipitation reaction. This Mn modified polyoxometalate catalyst has a maximum CO generation rate of 4625.0 μmol g-1 h-1 and a maximum H2 generation rate of 499.6 μmol g-1 h-1, with a selectivity of 90.3% for CO generation and 9.7% for H2 generation. This polyoxometalate photocatalyst can effectively reduce CO and inhibit the hydrogen precipitation reaction. It provides a new idea for the efficient photocatalytic carbon dioxide reduction (CO2RR) with polyoxometalate catalysts.

Significant improvement of photocatalytic hydrogen evolution performance in covalent organic frameworks: substituent fine-tuning

Six covalent organic frameworks with different substituents on the same backbone were synthesized to explore the relationship between their photocatalytic hydrogen precipitation efficiency and their structures.

Facile synthesis of ZnIn2S4@ZnS composites for efficient photocatalytic hydrogen precipitation

A ZnIn2S4@ZnS catalyst synthesized through a two-step process exhibits better photocatalytic H2 production performance (2.873 mmol g−1 h−1) than ZnIn2S4 (0.229 mmol g−1 h−1) under visible light due to the efficient interfacial electron transfer.

An anti-corrosive cellulose nanocrystal/carbon nanotube derived Zn anode interface for dendrite-free aqueous Zn-ion batteries.

Notorious zinc dendrite growth and hydrogen precipitation reactions disrupt the galvanic/stripping process at the electrolyte/electrode interface, which seriously affects the cycling stability of zinc anodes in aqueous zinc ion batteries. To improve the stability and reversibility of zinc anodes, we report an artificial SEI consisting of hydrophobic carbon nanocrystals and highly conductive carbon nanotube networks. This interfacial hydrophobicity effectively excludes free water from the surface of the zinc anode, which prevents water erosion and reduces the interfacial side reactions, resulting in a significant improvement in the cycling stability and coulombic efficiency of Zn plating/stripping. Benefiting from the reversible proton storage and fast desolvation kinetic behavior of the CNC/CNT interlayer, the stable cycling time of Zn/Zn symmetric batteries exceeds 700 h even at a high current density of 5 mA cm-2. The assembled CNC/CNT@Zn‖V2O5 full cell maintains a high capacity of 101.1 mA h g-1 after 5000 cycles (1.0 mA g-1). This study opens up a new area for expanding the use of organic compounds in zinc anode protection and offers a promising strategy for accelerating the development of aqueous zinc-ion batteries.

A rationally designed 3DTiO2@CdZnS heterojunction photocatalyst for effectively enhanced visible-light-driven hydrogen evolution.

Hydrogen production with higher efficiency and lower cost is of great significance for the sustainable development of energy. Zinc cadmium sulfide (CZS) is gaining more attention owing to its excellent photocatalytic properties. However, its development is greatly limited due to photogenerated charge recombination. In this work, an innovative design with a unique 3D morphology was introduced by integrating 3DTiO2 into CZS to form a novel 3DTiO2/CZS heterojunction photocatalyst. As a result, the optimized composite achieved a very high hydrogen production rate of 75.38 mmol h-1 g-1 under visible light, which is 2.4 times higher than that of the original CZS. It can also be greatly demonstrated through photoelectrochemical tests that this unique 3D morphology contributes to the effective separation of electrons and holes, thus dramatically improving the photocatalytic activity of 3DTiO2/CZS composites. The 3DTiO2/CZS composite has a rational energy band structure, which makes it more favorable for the hydrogen precipitation reaction. It is believed that such a modification strategy based on 3DTiO2 can be applied to other similar photocatalysts as well for boosting hydrogen evolution.

A new efficient catalyst: Metal-organic frameworks in electrocatalysis

Global warming and ecological degradation are becoming major environmental problems in the world today. To reduce energy loss and advocate green chemistry, the development of new energy sources is very important. Electrocatalytic technology has low environmental pollution and carbon emission because only electrons are involved and there is no need to add external fuel. And metal-organic framework (MOF), with its porous structure and large surface area, can provide an ideal reaction platform for electrocatalytic reactions. This paper first introduces the discovery and development of MOF materials, followed by a discussion of the current methods for designing MOFs from several perspectives, including pore size, conductivity, and active sites. Then the development of MOF materials with transition metal ions was analysed from the perspective of the elements Fe, Co, and Ni, which exhibit higher reaction rates in comparison with ordinary MOF materials in hydrogen precipitation reaction, oxygen absorption reaction and other reactions. Finally, this paper introduced several synthetic ideas and methods of MOF and reviewed the methods to synthesise MOF electrocatalytic materials.

Design of a photocatalyst combining graphdiyne (g-CnH2n-2) nanosheets with a PVP-modified co-metal coordination polymer and its hydrogen-evolution performance.

Metal coordination polymers are organometallic frameworks in which a metal and an organic ligand are linked via a dative bond. The material in question exhibits ultra-high porosity, large specific surface area, and abundant active sites, which can be customised in terms of morphology, size, and electronic structure through rational design. Graphdiyne, a novel two-dimensional carbon allotrope, boasts structural stability and enhanced electrical conductivity due to its hybridization of sp2 and sp carbons. A metal-organic framework of Co (MOF-67) was synthesized via hydrothermal synthesis. The introduction of polyvinyl pyrrolidone (PVP) served as a structural regulator and surfactant to obtain a more active metal coordination polymer (Co-MCPS). PVP, in its dual role, significantly amplified the catalytic performance of metal coordinate polymers, as demonstrated in a number of experiments. The incorporation of GDY onto the surfaces of MOF-67 and Co-MCPS induced an electron-rich isolation layer, which could effectively sequester oxidation sites, thereby enhancing the rate of charge carrier separation and hydrogen precipitation evolution efficiency.