Enhanced Hydrogen Evolution Reaction Activity Research Articles

Mo2C-MoS2 heterojunction a suitable and stable electrocatalyst for HER and supercapacitor Applications

In the present work, Mo2C-MoS2 heterojunction structures have been prepared by the wet impregnation method. For heterojunction species, the content of MoS2 was varied from 5 to 20% by weight. The effect of the loading content of MoS2 over Mo2C on hydrogen evolution reaction (HER) activity and electrochemical (EC) capacitance performance has been studied in detail. The Mo-C-S junction plays a key role in enhancing the HER activity and EC capacitance performance than the individual components. The prepared structures show enhanced HER activity with high current density ~36.2-78.3 mAcm-2 at very low applied potential (0.45 V), exhibiting a lower Tafel slope of 102.4 mVdec-1. The EC capacitor performance determined by CV and galvanic charge-discharge (GCD) reveals that the synthesized samples exhibit an electrochemical double-layer capacitor (EDLC, Cdl) behavior. The higher EDLC (43.9 mFcm-2) and specific capacitance (2Fg-1) obtained for the synthesized samples determine their potential applicability for the new generation supercapacitors.

Engineering multiphasic MoSe2/NiSe heterostructure interfaces for superior hydrogen production electrocatalysis

Constructing heterojunction nanocomposites with optimized active sites and interface electronic structures is promising for hydrogen evolution reaction (HER). Herein, we present an interface engineering strategy to fabricate two heterostructures, triphase MoSe2/NiSe-1 including 1T-MoSe2, 2H-MoSe2 and hexagonal phase NiSe (H-NiSe), and tetraphase MoSe2/NiSe-2 including 1T-MoSe2, 2H-MoSe2, H-NiSe and rhombohedral phase NiSe (R-NiSe). MoSe2/NiSe-1 exhibited remarkably enhanced HER activity with an overpotential of 30 mV at 10 mA cm−2, and negligible voltage change even when operated for 40 h. The strong electronic synergistic interaction between the different interfaces of mixed MoSe2/NiSe greatly enhanced the HER performance. Density functional theory calculations helped rationalize why the combination of three phases is more active, by increasing the interface electron concentration, facilitating electron transfer and decreasing the free energy ΔGH2O and ΔGH*. This work provides a rational strategy to design and assemble stable and high-performance multiphasic heterojunctioned HER electrocatalysts.

Origin of the Enhanced Hydrogen Evolution Reaction Activity of Grain Boundaries in MoS2 Monolayers

Origin of the Enhanced Hydrogen Evolution Reaction Activity of Grain Boundaries in MoS₂ Monolayers

Direct Thermal Enhancement of Hydrogen Evolution Reaction of On-Chip Monolayer MoS2.

MoS2 has drawn great attention as a promising alternative to Pt-based catalysts for the hydrogen evolution reaction (HER). However, it suffers from sluggish kinetics to drive the HER process because of inert basal planes. Here, an on-chip MoS2 monolayer (MoS2 ML) HER reactor was designed and fabricated to reveal direct thermal enhancement of MoS2 ML for the HER. The thermal effects generated efficient electron transfer in the atomic MoS2 ML and at the interface between the electrolyte and the catalyst, leading to enhanced HER activity. The MoS2 ML measured at a higher temperature (60 °C) possesses a significantly enhanced HER activity with a lower overpotential (90 mV at current densities of 10 mA cm-2), lower Tafel slope (94 mV dec-1), and higher turnover frequency (73 s-1 at an overpotential of 125 mV) compared to the results obtained at room temperature. More importantly, the findings are attractive toward understanding the thermal effect on 2D monolayers as well as the development of next-generation electrocatalysts.

Interface Engineering of Co/CoMoN/NF Heterostructures for High-Performance Electrochemical Overall Water Splitting.

The development of low‐cost and high‐efficiency catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte is still challenging. Herein, interfacial Co/CoMoN heterostructures supported on Ni foam (Co/CoMoN/NF) are constructed by thermal ammonolysis of CoMoO x . In 1.0 m KOH solution, Co/CoMoN/NF heterostructures exhibit excellent HER activity with an overpotential of 173 mV at 100 mA cm−2 and a Tafel slope of 68.9 mV dec−1. Density functional theory calculations indicate that the low valence state Co site acts as efficient water‐dissociation promoter, while CoMoN substrate has favorable hydrogen adsorption energy, leading to an enhanced HER activity. The Co/CoMoN/NF heterostructures also achieve high OER activity with an overpotential of 303 mV at 100 mA cm−2 and a Tafel slope of 56 mV dec−1. Using Co/CoMoN/NF heterostructures as the cathode and anode, the alkaline electrolyzer requires a low voltage of 1.56 V to reach the current density of 100 mA cm−2 along with superior long‐term durability. This study provides a new design strategy toward low‐cost and excellent catalysts for water splitting.

Conducting scaffold supported defect rich 3D rGO-CNT/MoS2 nanostructure for efficient HER electrocatalyst at variable pH

Designing a suitable noble metal-free electrocatalyst for the hydrogen evolution reaction (HER) is enduring challenge. Molybdenum disulfide (MoS 2 ) shows structural and electronic advantages as potential HER electrocatalyst. The structural and electronic design of MoS 2 electrocatalysts should be considered to improve the efficiency and stability of MoS 2 based electrodes. This report shows that the presence of synergistic interaction significantly improves the HER electrocatalytic activity of defect-rich 3D rGO-CNT/MoS 2 composites. The Defect-rich conductive scaffold supported nanostructures can improve the catalytic performance and stability. Lowering of the HOMO-LUMO gap supervises the charge transfer resistance of the nanostructure . The turnover frequency value indicates that 3D rGO-CNT/MoS 2 acts as the potential electrocatalyst and the overpotential observed at a current density of 10 mA cm −2 in acidic and alkaline media are 88 mV and 172 mV, respectively. This investigation provides a new idea to develop molybdenum disulfide and scaffolds based 3D nanostructures to improve the inherent electrocatalytic activity of HER. • Synthesis of conducting scaffold supported 3D rGO-CNT/MoS 2 nanostructure. • Physicochemical analysis leads to defect rich nanostructure with different S/Mo ratio. • Formation of conducting scaffold based nanocomposite enhance HER activity. • 3D nanostructure provide extra operational stability in acidic and alkaline pH.

Vanadium doped FeP nanoflower with optimized electronic structure for efficient hydrogen evolution

Reasonable design of hydrogen evolution reaction (HER) electrocatalyst from the perspective of electronic structure is a vital way to optimize the catalytic activity. Mono-metallic iron-based phosphates have been shown to be active toward HER, but their performance remains unsatisfactory despite their abundant reserves and low preparation cost. Here, guided by the d-band center and band structure theories, V-doped FeP nanoflower grown directly on iron foam are constructed. Combining the density functional theory (DFT) simulations with physical characterizations reveal that the enhanced HER activity is mainly attributed to the lowed d-band central position, increased water dissociation capacity, decreased hydrogen formation energy barrier and reduced charge transfer impedance. As a HER catalyst in 1 M KOH, the obtained V-FeP shows low overpotentials of ∼149, ∼246 and ∼290 mV to deliver the current densities of 100, 500 and 1000 mA cm−2 with at least 24 h. When coupled with other highly active oxygen evolution reaction (OER) catalyst (NiFe-LDH/IF), the NiFe-LDH/IF(+) || V-FeP/IF(-) pair also performs a low cell voltage and over 100-h stability at high current density of 1000 mA cm−2, which endows it a large potential in the practical electrolytic water industry. Our work may provide a reference for the enhancement of inert and low-cost HER-active iron phosphide.

P and Se-codopants triggered basal plane active sites in NbS2 3D nanosheets toward electrocatalytic hydrogen evolution

Promoting the intrinsic activity and accessibility of basal plane sites in transition metal dichalcogenides (TMDs) is an important way to optimize their catalytic performance for energy conversion and storage. Here, a simple liquid-phase phosphating selenization pyrolysis method is developed to prepare P and Se co-doped niobium disulfide (NbS2) 3D nanosheets with active basal plane for efficient catalyzing hydrogen evolution reaction (HER). Experimental results indicate that the P and Se co-doped NbS2 3D nanosheets exhibit significantly enhanced HER activity and stability compared to their undoped counterparts. It realizes 165 mV decreased overpotential at 10 mA cm−2 and a stable durability over 40 h continuous operation at 14 mA cm−2 without observable fading. Density functional theory (DFT) studies suggest that the P dopant is to activate the adjacent original inert Nb sites, where both S and Nb sites in P, Se co-doped NbS2 monolayer can together act as the active sites for HER. Furthermore, the addition of selenium can stabilize the catalytic activity. Our work provides a promising approach and theoretical framework for improving the electrocatalytic HER performance of NbS2, and may have general guidelines for other transition metal disulfides.

MWCNT-modified MXene as cost-effective efficient bifunctional catalyst for overall water splitting.

Utilization of cost-effective, bifunctional, and efficient electrocatalysts for complete water splitting is desirable for sustainable clean hydrogen energy. In last decade, MXenes, a family of emerging two-dimensional (2D) materials with unique physiochemical properties, enticed scientists because of their use in different applications. However, insufficient electron transport, lower intrinsic chemical activity and limited active site densities are the factors inhibiting their use in electrocatalytic cells for hydrogen production. Here, we have presented material design to address this issue and introduced carbon nanotubes (CNTs) on V2CTx MXene sheets for conductive network channels that enhance the ion diffusion for enhanced electrochemical activity. The SEM reveals the uniform dispersion of the MWCNTs over the MXene surface that resulted in the formation of conductive network channels and enhances reaction kinetics. The as-synthesized electrocatalyst was subjected to linear sweep voltammetry (LSV) measurements for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The hybrid catalyst M2 exhibited an enhanced HER activity with a lower over-potential of 27 mV which is comparable to commercially available Pt-based catalysts (32 mV). Similarly, an enhanced OER activity was observed with a lower over-potential of 469 mV as compared to pristine V2CTx MXene. The electrocatalyst was subjected to a durability test through chronoamperometry and was observed to be stable for 16 hours. Hence, this study opens a new avenue for future cost-effective efficient catalysts for overall water splitting as a solution to produce clean hydrogen.

Metal-organic framework (MOF)-derived plate-shaped CoS1.097 nanoparticles for an improved hydrogen evolution reaction.

Metal-organic framework (MOF)-derived transition metal sulfides are viewed as reliable, cost-effective, and alternative hydrogen evolution reaction (HER)-efficient electrocatalysts. They have been used to replace platinum (and their alloys) for production of renewable energy carriers such as hydrogen. Progress towards development of non-precious transition-metal sulfides through different synthetic routes to obtain unique morphological nanostructures with enhanced HER activity is challenging. We introduced a transition-metal sulfide, cobalt sulfide (CoS1.097), derived from a cobalt MOF [Co-BPY-DDE] by following facile, one-step solvothermal sulfurization. By varying the sulfurization temperature (from 140 °C to 180 °C) during the solvothermal method, three cobalt-sulfide products were obtained: CoS1.097-140, CoS1.097-160, and CoS1.097-180, respectively. Temperature variation had a vital role in optimizing the HER activity of the electrocatalyst. Besides, notable plate-shaped cobalt sulfide nanoparticles (CoS1.097-160) required overpotential of 163 mV to deliver a current density of 10 mA cm-2 with a low Tafel slope of 53 mV dec-1, thereby demonstrating faster reaction kinetics during the evolution of molecular hydrogen. Furthermore, 25 h of long-term stability of the electrocatalyst reflected its practical applicability in acidic media. CoS1.097-160 had uniform plate-shaped morphology and large electrochemical active surface area, which contributed to enhanced electrochemical performance through water electrolysis.

Porous TiNi3-based intermetallics as active and robust monolith catalysts for hydrogen evolution.

Electrochemical water splitting offers an appealing method to produce hydrogen as we attempt to achieve global carbon neutrality. However, the lack of earth-abundant, low-cost, active, and stable catalysts at large current densities severely hinders its industrial applications. TiNi3-based intermetallics as porous monolith catalysts (PMCs) exhibit an efficient hydrogen evolution reaction (HER) performance (an overpotential of 244 mV to afford 200 mA cm-2) and excellent stability in 1 M KOH. Theoretical calculations demonstrate that the synergetic effect between Ni and Mo can enhance HER activity. PMCs provide a new strategy to design catalysts with efficient and stable performance for industrial applications.

Self-supported amorphous TaNx(Oy)/nickel foam thin film as an advanced electrocatalyst for hydrogen evolution reaction.

Chemical vapor deposited (CVD) amorphous tantalum-oxy nitride film on porous three-dimensional (3D) nickel foam (TaNx(Oy)/NF) utilizing tantalum precursor, tris(diethylamino)(ethylimino)tantalum(V), ([Ta(NEt)(NEt2)3]) with preformed Ta-N bonds is reported as a potential self-supported electrocatalyst for hydrogen evolution reaction (HER). The morphological analyses revealed the formation of thin film of core-shell structured TaNx(Oy) coating (ca. 236 nm) on NF. In 0.5 M H2SO4, TaNx(Oy)/NF exhibited enhanced HER activity with a low onset potential as compared to the bare NF (-50 mV vs. -166 mV). The TaNx(Oy)/NF samples also displayed higher current density (-11.08 mA cm-2vs. -3.36 mA cm-2 at 400 mV), lower Tafel slope (151 mV dec-1vs. 179 mV dec-1) and lower charge transfer resistance exemplifying the advantage of TaNx(Oy) coating towards enhanced HER performance. The enhanced HER catalytic activity is attributed to the synergistic effect between the amorphous TaNx(Oy) film and the nickel foam.

Saturated hydrogen regulated ti coordination of metallic tih2/ti electrode via in-situ electrochemical hydrogenation for enhanced hydrogen evolution reaction

The hydrogen adsorption energy is an important factor of hydrogen evolution reaction (HER) intrinsic catalytic activity. Herein, we propose a facile strategy to synthesize metallic titanium hydride (TiH2) via in-situ electrochemical hydrogenation of titanium oxide (TiO2) in acidic media. The saturated H tunes Ti coordination reduces the ΔGH* and resistance of TiH2, which improves the H coverage and accelerates the charge transfer. The obtained TiH2/Ti possesses the enhanced HER activity with large current density (1400 mA cm−2 at −1.13 V vs. RHE) and superstability (1350 mA cm−2 for 88 h). Furthermore, large-sized and porous TiH2/Ti is produced by laser to construct the TiH2/Ti||IrO2/Ti electrolyzer, which confirmed that the self-supporting electrode with gas diffusion channel was beneficial for water electrolysis. This work provides an universal method to regulate metal coordination through in-situ electrochemical hydrogenation for the enhanced HER activity.

Pt NPs-loaded siloxene nanosheets for hydrogen co-evolutions from Zn-H2O fuel cells-powered water-splitting

Siloxene features abundant functional groups and oxygen vacancies, which facilitates the ultrafine platinum nanoparticles loading for catalyzing hydrogen evolution reaction (HER). Herein, a siloxene-p-Pt-2 h composite has been fabricated with an ultralow platinum loading on siloxene (0.56 wt%), which shows greatly enhanced HER activity featuring an ultralow overpotential (η10 = 23 mV). Attractively, the siloxene-p-Pt-2 h has been applied as a HER catalyst in a Zn-H2O fuel cell, demonstrating a high power density of 157 mW cm−2 in coupling with the cathode hydrogen evolution. Moreover, a coupled configuration between two Zn-H2O fuel cells in series and the cell-powered hydroxide electrolyzer achieves the efficient hydrogen co-productions co-catalyzed by the HER catalysts. The excellent HER performance is attributed to the hydrophilic character and the optimal Gibbs free energy via the strong interaction between the siloxene and platinum nanoparticles. This work provides a novel design of self-powered co-productions of hydrogen.

Defect-Assisted Anchoring of Pt Single Atoms on MoS2 Nanosheets Produces High-Performance Catalyst for Industrial Hydrogen Evolution Reaction.

Pt-based catalysts are currently the most efficient electrocatalysts for the hydrogen evolution reaction (HER), but the scarcity and high cost of Pt limit industrial applications. Downsizing Pt nanoparticles (NPs) to single atoms (SAs) can expose more active sites and increase atomic utilization, thus decreasing the cost. Here, a solar-irradiation strategy is used to prepare hybrid SA-Pt/MoS2 nanosheets (NSs) that demonstrate excellent HER activity (the overpotential at a current density of 10 mA cm-2 (η10 ) of 44 mV, and Tafel slope of 34.83 mV dec-1 in acidic media; η10 of 123 mV, and Tafel slope of 76.71 mV dec-1 in alkaline media). Defects and deformations introduced by thermal pretreatment of the hydrothermal MoS2 NSs promote anchoring and stability of Pt SAs. The fabrication of Pt SAs and NPs is easily controlled using different Pt-precursor concentrations. Moreover, SA-Pt/MoS2 produced under natural sunlight exhibits high HER performance (η10 of 55mV, and Tafel slope of 43.54mV dec-1 ), which indicates its viability for mass production. Theoretical simulations show that Pt improves the absorption of H atoms and the charge-transfer kinetics of MoS2 , which significantly enhance HER activity. A simple, inexpensive strategy for preparing SA-Pt/MoS2 hybrid catalysts for industrial HER is provided.

Electrodeposition of the manganese-doped nickel-phosphorus catalyst with enhanced hydrogen evolution reaction activity and durability

Hydrogen technology is widely considered a novel clean energy source, and electrolysis is an effective method for hydrogen evolution. Therefore, efficient hydrogen evolution reaction (HER) catalysts are urgently needed to replace precious metal catalysts and meet ecological and environmental protection standards. Herein, Ni–Mn–P electrocatalysts are synthesized using facile electrodeposition technology. The influence of the Mn addition on the catalytic behavior is studied by the comprehensive analysis of catalytic performance and morphology of the catalysts. Among them, the Ni–Mn–P0.01 catalyst exhibits small coral-like structures, greatly improving the adsorption and desorption of hydrogen ions and reducing the overpotential hydrogen evolution. Consequently, overpotential at 10 mA cm−2 electric current density is 113 mV, and the value of the Tafel slope achieves 74 mV/dec. Furthermore, the Ni–Mn–P catalyst shows long-time (20 h) stability at current densities of 10 and 60 mA/cm2. The results confirm that the synergistic effect of Ni, Mn, and P accelerates the electrochemical reaction. Meanwhile, the addition of manganese element can change the micromorphology of the catalyst, thereby exposing more active sites to participate in the reaction, enhancing water ionization, improving the catalytic performance. This study opens a new way toward improving the activity of the catalyst by adjusting Mn concentration during the electrodeposition process.

Single-Atom Co Doped in Ultrathin WO3 Arrays for the Enhanced Hydrogen Evolution Reaction in a Wide pH Range.

Owing to the scarcity of Pt, low-cost, stable, and efficient nonprecious metal-based electrocatalysts that can be applied in a wide pH range for the hydrogen evolution reaction (HER) are urgently required. Herein, a highly efficient and robust HER catalyst that is applicable at all pH values is fabricated, containing isolated Co-single atomic sites anchored in the self-supported WO3 arrays grown on Cu foam. At a current density of 10 mA cm-2, the HER overpotentials are 117, 105, and 149 mV at pH values of 0, 7, and 14, respectively, which are significantly lower than those of the undoped WO3, suggesting superior electrocatalytic H2-evolution activity at all pH values. The catalyst also exhibits long-term stability over a wide pH range, particularly in an acidic medium over 24 h, owing to the excellent anticorrosion properties of WO3. Density functional theory calculations prove that the enhanced HER activity is attributed to the isolated Co sites because these optimize the adsorption energy of H* species on WO3. Moreover, the high electrical conductivity of Co-doped WO3 and the three-dimensional array structure supported on the porous metal support afford a catalyst with suitable HER kinetics to enhance the catalytic performance.

Interface engineering of Ni0.85Se/Ni3S2 nanostructure for highly enhanced hydrogen evolution in alkaline solution

Interface engineering is considered as an effective strategy to improve the hydrogen evolution reaction (HER) performance of electrocatalysts. Herein, the Ni0.85Se/Ni3S2 heterostructure grown on nickel foam (NF) is synthesized via successive wet-chemical processes. The obtained Ni0.85Se/Ni3S2 heterostructure is firstly investigated as an HER electrocatalyst in alkaline media and exhibits more excellent electrochemical properties over Ni3S2. And it delivers a low overpotential of 145 mV at a current density of −10 mA cm−2, and superior stability. Based on the analysis of high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectra (XPS), the enhanced HER activity is due to the modulation of surface electronic structure, ascribing from the construction of heterointerface between Ni0.85Se and Ni3S2. Meanwhile, the Ni0.85Se/Ni3S2 heterostructure prepared in this work is also verified to be employed as a promising alternative to noble metal catalysts in HER.

Waste‐yeast biomass as nitrogen/phosphorus sources and carbon template: Environment‐friendly synthesis of N,P‐Mo2C nanoparticles on porous carbon matrix for efficient hydrogen evolution

Tailor-made advanced electrocatalysts with high active and stable for hydrogen evolution reaction (HER) play a key role in the development of hydrogen economy. Herein, a N,P-co-doped molybdenum carbide confined in porous carbon matrix (N,P-Mo2C/NPC) with a hierarchical structure is prepared by a resources recovery process. The N,P-Mo2C/NPC compound exhibits outstanding HER activity with a low overpotential of 84 mV to achieve 10 mA/cm2, and excellent stability in alkaline media. The electrochemical measurements confirm that the enhanced HER activity of N,P-Mo2C/NPC is ascribe to the synergy of N,P-codoped and porous carbon matrix. Density functional theory calculations further reveal that the electron density of active sites on Mo2C can be regulated by the N/P doping, leading to optimal H adsorption strength. In this work, the proof-of-concept resource utilization, a microorganism derived molybdenum carbide electrocatalyst for HER is fabricated, which may inaugurate a new way for designing electrocatalysts by the utilization of solid waste.

Geometric and electronic modulation of fcc NiCo alloy by Group-Ⅵ B metal doping to accelerate hydrogen evolution reaction in acidic and alkaline media

Bimetallic nickel–cobalt (Ni-Co) alloy has been regarded as an emerging class of material for the electrochemical hydrogen evolution reaction (HER). However, it operates at an overpotential significantly above the thermodynamic requirement. Here we present a facile one-step electrochemical reduction approach to incorporate fcc NiCo alloy with ⅥB group transition metals (M−NiCo, M = chromium (Cr), molybdenum (Mo), or tungsten (W)). This method enables to control the induction time of protrusion growth (τ) to produce hierarchical structure by imposing high current density (-0.6 A cm−2) and strong electric field on the cathode. Herein, W-NiCo holey nanotower arrays show tremendously enhanced HER activity compared with pristine NiCo alloy, which provides an overpotential of 109.2 mV (reduced by 58.7%) to achieve a current density of −10 mA cm−2, with a Tafel slope of 110.3 mV dec-1 in alkaline medium. The same law applies to the acid electrolyte with an overpotential of 78.5 mV (reduced by 66.1%) and low Tafel slop of 56.6 mV dec-1. Based on the experimental and theory analysis, We find W-doping can promote more active sites exposed, tune the electron configuration, moderate the gibbs free energy of the H intermediate, and accelerate the desorption of H2. It makes the rate-determining step change from Volmer to Heyrovsky reaction and finally surmount the limit of sluggish dynamics. The novel route provides an efficient doping control on Ni-based hierarchical alloys via 4f-orbital electronic and geometric structure engineering, which suggests an environmentally friendly method for energy-related process in practical applications.