Electrochemical Hydrogen Evolution Reaction Research Articles

Theoretical and experimental investigations of vanadium pentoxide–based electrocatalysts for the hydrogen evolution reaction in alkaline media

AbstractA key approach towards better realization of intermittent renewable energy resources, namely, solar and wind, is green electrochemical hydrogen production from water electrolysis. In recent years, there have been increasing efforts aimed at developing noble metal-free electrocatalysts that are earth-abundant and electroactive towards hydrogen evolution reaction (HER) in alkaline electrolytes, wherein an initial water dissociation step is followed by a two-electron transfer cathodic reaction. Although relatively earth-abundant, vanadium-based electrocatalysts have been sparsely reported due to subpar electroactivity and kinetics towards water electrolysis in general and alkaline electrolysis in specific. Herein, we investigate the fine-tuning of orthorhombic V2O5-based electrocatalysts as candidates for HER through a scalable two-step sol–gel calcination procedure. Briefly, surface-induced anionic oxygen deficiencies and cationic dopants are synergistically studied experimentally and theoretically. To that end, first-principle facet-dependent density function theory (DFT) calculations were conducted and revealed that the coupling of certain dopants on V2O5 and co-induction of oxygen vacancies can enhance the catalytic HER performance by the creation of new electronic states near the Fermi level (EF), enhancing conductivity, and modulating surface binding of adsorbed protons, respectively. This was reflected experimentally through kinetically non-ideal alkaline electrochemical HER using Zn0.4V1.6O5 whereby − 194 mV of overpotential was required to attain − 10 mA/cm2 of current density, as opposed to pristine V2O5 which required 32% higher overpotential requirement at the same conditions. The disclosed work can be extended to other intrinsically sluggish transition metal (TM)–based oxides via the presented systematic tuning of surface and bulk microenvironment modulation. Graphical Abstract

Aqueous pH influence on the electrocatalytic hydrogen evolution reaction with carbon nanotube-supported diiron dithiolato compound

Biomimetic chemistry on structure, function and external environment of [FeFe]-hydrogenases for hydrogen evolution reaction (HER) has shown a promising way to develop non-precious metal electrocatalysts for H2 production in the current Pt-dominated HER system. Herein, three new diiron dithiolato compounds [{(μ-SCH2)2N(C6H4CH2CO2R)}Fe2(CO)6] (R = H (1), C6H4CHO-p (2), and C6H4Me-m (3)) were first prepared and identified as a library of [FeFe]-hydrogenase models in this work. Subsequently, the as-prepared diiron molecule 2 can be covalently attached onto carbon nanotubes (CNTs), resulting in the obtainment of target CNT-supported [FeFe]-hydrogenase model labeling as covalent hybrid 2Fe2S-f-CNT. Notably, the electrocatalytic HER performance and stability of the resulted hybrid 2Fe2S-f-CNT immobilized respectively on a gassy carbon (GC) electrode are systematically studied and compared in 0.1 M KOH (pH = 13), 0.1 M phosphate buffer (pH = 7), and 0.05 M H2SO4 (pH = 1) aqueous solutions by various spectroscopic and electrochemical techniques. The result has shown that the higher electrocatalytic HER activity is observed in alkaline solution (pH = 13) relative to neutral and acidic solutions (pH = 7, 1), being attributed to the different electrochemical HER processes of diiron cluster in wide pH aqueous media as revealed by post operando analysis.

Tuning the electrocatalytic activity of MoS2 nanosheets via the in situ hybridization with ruthenium and graphene network

The quest for highly efficient, stable, and non-precious electrocatalysts as alternatives to Pt in the hydrogen evolution reaction (HER) at ambient temperature is paramount. Two-dimensional (2D) layered transition metal dichalcogenides (TMDs), notably MoS2, have emerged as promising noble-metal-free candidates. However, MoS2′s limited active edge sites and sluggish electron transfer kinetics present challenges in achieving efficient HER activity under both acidic and basic conditions. In this study, we introduce a composite catalyst composed of 2D MoS2 nanosheets enveloped by graphene networks, with uniform dispersion of ruthenium (Ru) nanoparticles within the extended 2D structure. This ternary hybrid catalyst exhibits excellent catalytic activity, with a low onset overpotential of 60 mV at 10 mA cm−2, a small Tafel slope of 38 mV dec-1, and remarkable durability during continuous 10-hour operation at 100 mV potential in 1.0 M KOH, without substantial activity loss. The conductive graphene support effectively prevents the restacking of exfoliated MoS2 nanosheets, enhancing mass transport and charge transfer kinetics. Ru incorporation induces the partial phase transformation of MoS2 from its trigonal (2H) to octahedral (1 T) phase, concurrently generating sulfur vacancies. The induced phase transformation not only activates the inert basal planes of MoS2 but also reduces the energy barrier for the adsorption/desorption of H* intermediates. Beyond the structural advantages, the intrinsic synergistic effects, primarily related to electronic structure modulation and defect engineering, contribute significantly to the enhanced electrochemical HER performance. In summary, this study not only introduces an efficient, cost-effective alternative to Pt-based electrocatalysts but also lays the foundation for designing other TMD-based hybrid catalysts, characterized by abundant exposed active sites and reduced barriers for hydrogen binding energy, thereby advancing electrochemical hydrogen production.

Role of cooperative effect by Mo and Pd mixed micellar assemblies for displaying the Pt/C like hydrogen evolution reaction

Cooperative effect as well as interfacial engineering are crucial factors for the development of electrochemical hydrogen evolution reaction (HER). Keeping this aspect in mind, a novel mixed micellar film using dodecylamine molybdenum (III) trichloride (MoDDA(I)) and dodecylamine palladium (II) dichloride (PdDDA(I)) was fabricated for electrochemical HER. The mixed micellar film was characterized by various instrumentation techniques to explore its structure and composition i.e. FESEM, AFM, FTIR. In addition, XPS was inserted to understand the underlying mechanism before and after electrolysis. The fabricated surface of mixed micelles was found to be hydrophobic. The efficiency of mix-metallomicelles as an electrocatalyst was checked in acidic media for electrochemical HER. The prepared reverse micellar film was activated by polarization cycles due to the in-situ reduction of metallic components. These metallic cores act as active centers for electrocatalytic HER. The HER activity of Mo-PdDDA(I) was found to be superior as compared with Pt/C. The prepared mixed micelles displayed 29.2 mV dec−1 Tafel slope. First, Mo and Pd based mixed micelles were prepared using a one-pot method. Benefiting from the role of organic media, MoDDA(I) and PdDDA(I) were able to orient in the form of reverse micelles. Wherein, Mo and Pd metal ions are present in the core of the micelles. The excellent activity exhibited by the formation of mix-metallomicelles, a synergic effect between metal ions, and interfacial engineering introduced by the surfactant moiety, which in turn facilitates the adsorption and activation of hydrogen ions on the electrode surface. Additionally, the mixed micelles provide a high surface area for the electrochemical reaction and enhance the conductivity of the electrode.

Comparative study on various morphologies of WS2 for electrochemical hydrogen evolution reaction

Nowadays, the advancement of cost-effective and efficient electrocatalysts holds significant importance in facilitating the progress of high-performance electrochemical hydrogen evolution reaction (HER). Tungsten disulfides (WS2) are well recognized as highly promising electrocatalysts for HER due to their exceptional catalytic performance, outstanding stability, and comparatively affordable price. In this study, we used ammonium metatungstate hydrate and thioacetamide as precursors to fabricate WS2 nanoflowers (NFs) by hydrothermal method, whereas WS2-flakes were prepared from ammonium tetrathiotungstate through the thermolysis technique. These structures were evaluated for HER electrocatalytic activity in acidic media. The results revealed that WS2-NFs exhibit higher catalytic activity than WS2-flakes, with an overpotential of 325 mV to obtain a current density of 10 mA cm−2 and a Tafel slope of 92.3 mV dec−1. This performance was attributed to the larger electrochemically active surface area of WS2-NFs compared to WS2-flakes materials. The results of this study could bring the basis for further studies on the synthesis of WS2-based catalytic materials for HER. ® 2023 Journal of Science and Technology - NTTU

Design of bifunctional synergistic NiMoO4/g-C3N4 nanocomposite for the augmentation of electrochemical water splitting and photocatalytic antibiotic degradation performances

Developing cost-effective and efficient electrocatalysts across a wide pH range poses a significant challenge in electrochemical water splitting for energy generation. Designing nanocomposites with well-tuned interfaces can significantly boost electrocatalytic performance. Here, we present an effective and durable g-C3N4 (CN) modified NiMoO4 (NM) electrocatalysts coated on nickel foam (NF) for maximizing electrochemical water splitting performance. We optimized the nanocomposite for effective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity in acidic, neutral, and alkaline electrolytes by adjusting the weight ratio of the g-C3N4. The NMCN-4/NF electrode exhibits the best electrochemical HER activity under alkaline and acidic conditions with lower overpotentials of −0.114 and −0.158 V, respectively, to achieve −10 mA cm−2. The highest HER activity was −127.3 mA cm−2 for the NMCN-4/NF under acidic conditions, which is 3.6 and 2.98 times greater than the pristine NM and CN-coated NF electrodes, respectively. Under an alkaline medium, the highest OER activity of the NMCN-4/NF was 152.9 mA cm−2, which is 4.07 and 2.75 folds higher than NM/NF and CN/NF electrodes, respectively. Besides, the NMCN-4 catalysts showed excellent photocatalytic degradation behavior on antibiotic pollutants with a percentage of 96.68%, which is 3.2 and 3.01% higher than pristine NM and CN catalysts, respectively. The NMCN-4 electro /photocatalysts exhibit an impressive balance of electro /photocatalytic efficiency and stability.

Electrocatalytic Hydrogen Evolution of Immobilized Copper Complex on Carbonaceous Materials: From Neutral Water to Seawater.

Electrochemical hydrogen evolution reaction (HER) is an appealing strategy to utilize renewable electricity to produce green H2. Moreover, use of neutral-pH electrolyte such as water and seawater for the HER has long been desired for eco-friendly energy production that aligns with net zero emission goal. Herein, new heterogeneous catalysts were developed by dispersing an HER-active copper complex containing N4-Schiff base macrocycle (CuL) on carbonaceous materials, i. e. multi-walled carbon nanotube (CNT) and graphene oxide (GO), via non-covalent interaction and investigated their HER performance. It was found that CuL/GO exhibited higher HER activity than CuL/CNT, possibly due to its significantly larger amount of CuL immobilized onto GO. In addition, CuL/GO showed satisfactory HER performance in a neutral (pH 7) NaCl electrolyte solution. Notably, the performances of CuL/GO were boosted up when performed in natural seawater sample with the faradaic efficiency of 70 % and 3 times higher amount of H2 at -0.6 V vs reversible hydrogen electrode (RHE), in comparison to the HER in a NaCl electrolyte. Furthermore, it possessed a low overpotential of 139 mV at -10 mA/cm2. This demonstrated the potential use of CuL/GO as an effective HER catalyst in seawater for further sustainable development.

Preparation and application research of transition metal phosphides

Due to the serious environmental pollution in the world, the shortcut to harmonious development is to improve traditional disposable energy and identify new energy sources that can be utilized. The current problem that human society must solve is to discover and use efficient and inexhaustible new energy sources, among which electrolytic water technology is an effective way to develop clean energy. In recent years, researchers have focused on producing hydrogen by electrolyzed water, but the intermediate hydrogen evolution reaction and the oxygen evolution reaction are relatively slow kinetic processes, and they cannot give the factory a large range of electrolytic water hydrogen production work and push down the commercialization process, so improving the rate of electrolytic water process must be an efficient catalyst. Transition metal phosphide is one of the non-precious metal catalysts in the electrochemical hydrogen evolution reaction and oxygen evolution reaction. Transition metal phosphide can promote rapid change of chemical reaction rate, and it has the characteristics of being cheap and easy to operate so it has a great prospect in the electrolysis of water. In this experiment, the oxygen evolution performance was optimized based on the crystal surface regulation of cobalt-doped transition metal nickel phosphide. The optimal reduction time and a small overpotential (60 mV) were obtained by using sodium borohydride to reduce the sample.

Impact of Co:Fe cations composition in amorphous and mesoporous cobalt iron phosphate electrocatalysts synthesized by SILAR method on durable electrochemical water splitting

Efficient and durable electrocatalysts are crucial for energy conversion devices that perform the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The structural and morphological characteristics of the electrocatalyst can significantly impact the HER/OER performance. Therefore, it is essential to develop a high-performing electrocatalyst with desired properties using a simple and cost-effective chemical process. So, herein, successive ionic layer adsorption and reaction (SILAR) deposited amorphous, hydrous cobalt iron phosphate (CFP) thin film electrocatalysts are implemented toward electrochemical water splitting. Moreover, in the present work, the molar proportions of cobalt and iron were streamlined to study their synergistic effect on electrochemical HER and OER performance. The electrode of best-performing (CFP–S2) requires the lowest overpotentials of 242 mV for OER and 67.9 mV for HER at a current density of 10 mA/cm2, which maintains its activity after 24 h. The alkaline water splitting into a similar electrolytic bath using two electrode systems was demonstrated for 100 h with the lowest overpotential of 1.72 V. The remarkable electrochemical performance and postmortem analysis unambiguously demonstrate that CFP electrodes are a highly promising and robust option for long-duration water-splitting devices, and the facile SILAR method for scalable CFP electrode synthesis indicates enormous potential for commercial applications.

Top-down nanostructured multilayer MoS2 with atomically sharp edges for electrochemical hydrogen evolution reaction

Cost-efficient and readily scalable platinum-free electrocatalysts are crucial for a smooth transition to future renewable energy systems. Top-down activation of MoS2 promises the production of sustainable hydrogen evolution electrocatalysts from the Earth-abundant molybdenite ore. Here, the deterministic nanopatterning of multilayer MoS2 with numerous zigzag edges is explored as a pathway to enhance hydrogen evolution reaction (HER). Nanopatterned single-nanosheet MoS2 electrodes are assessed by two highly localized electrochemical techniques: selected area voltammetry (with lithography-defined regions of electrode-electrolyte contact) and Scanning ElectroChemical Microscopy (SECM). The nanopatterning effect is the most pronounced after prolonged electrochemical cycling in an acidic electrolyte. The electrocatalytic hydrogen evolution activity of edge-enriched electrodes is dramatically enhanced: the maximum electrochemical current density (jmax) achieved at -510 mV vs. reversible hydrogen electrode (mVRHE) is increased by two orders of magnitude, reaching >300 mA⋅cm−2. Both the η10 and η100 overpotentials are significantly reduced as well. Meanwhile, pristine MoS2 shows just ≈6 times jmax increase (≈30 mA⋅cm−2) after the very same cycling. The increased electrocatalytic activity comes with electrode morphology degradation, evidenced by ex-situ scanning electron microscopy. SECM directly visualizes stronger HER activity in the regions with densely located zigzag edges. Intense white light illumination significantly boosts HER on MoS2 electrodes due to the photo-enhanced MoS2 conductivity. These results improve the understanding and reveal the limitations of MoS2-based electrocatalytic water splitting.

Recent advances of metal suboxide catalysts for carbon‐neutral energy applications

AbstractMetal suboxides have emerged as a class of promising candidates for many electrocatalytic applications owing to their enhanced electrical conductivity and chemical activities. In this review, we have summarized the recent progress of metal suboxides. We have firstly introduced the discovery of metal suboxides, and their categories according to element tables. Then various metal suboxides synthetic methods have been systematically illustrated involving solid‐state synthesis, high‐temperature synthesis, low‐temperature synthesis and plasma‐driven synthetic methods, etc. In addition, their applications have been demonstrated in the field of water, carbon and nitrogen cycle‐based energy catalysis technologies involving electrochemical hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction, urea oxidation reaction, methanol oxidation reaction, nitrogen reduction reaction and nitrate reduction reaction, etc. Finally, we make a brief conclusion about the developments of metal suboxides, giving an outlook for future research challenges. These insights are expected to hold promise for developing metal suboxide catalysts toward practical applications.

Phase-Transition of Mo2 C Induced by Tungsten Doping as Heterointerface-Rich Electrocatalyst for Optimizing Hydrogen Evolution Activity.

Electrochemical hydrogen evolution reaction (HER) from water splitting driven by renewable energy is considered a promising method for large-scale hydrogen production, and as an alternative to noble-metal electrocatalysts, molybdenum carbide (Mo2 C) has exhibited effective HER performance. However, the strong bonding strength of intermediate adsorbed H (Hads ) with Mo active site slows down the HER kinetics of Mo2 C. Herein, using phase-transition strategy, hexagonal β-Mo2 C could be easily transferred to cubic δ-Mo2 C through electron injection triggered by tungsten (W) doping, and heterointerface-rich Mo2 C-based composites, including β-Mo2 C, δ-Mo2 C, and MoO2 , are presented. Experimental results and density functional theory calculations reveal that W doping mainly contributes to the phase-transition process, and the generated heterointerfaces are the dominant factor in inducing remarkable electron accumulation around Mo active sites, thus weakening the Mo─H coupling. Wherein, the β-Mo2 C/MoO2 interface plays an important role in optimizing the electronic structure of Mo 3d orbital and hydrogen adsorption Gibbs free energy (ΔGH* ), enabling these Mo2 C-based composites to have excellent intrinsic catalytic activity like low overpotential (η10 = 99.8mV), small Tafel slope (60.16 dec-1 ), and good stability in 1m KOH. This work sheds light on phase-transition engineering and offers a convenient route to construct heterointerfaces for large-scale HER production.

Bulk‐Heterojunction Electrocatalysts in Confined Geometry Boosting Stable, Acid/Alkaline‐Universal Water Electrolysis

AbstractAlkaline water splitting electrocatalysts have been studied for decades; however, many difficulties remain for commercialization, such as sluggish hydrogen evolution reaction (HER) kinetics and poor catalytic stability. Herein, by mimicking the bulk‐heterojunction morphology of conventional organic solar cells, a uniform 10 nm scale nanocube is reported that consists of subnanometer‐scale heterointerfaces between transition metal phosphides and oxides, which serves as an alkaline water splitting electrocatalyst; showing great performance and stability toward HER and oxygen evolution reaction (OER). Interestingly, the nanocube electrocatalyst reveals acid/alkaline independency from the synergistic effect of electrochemical HER (cobalt phosphide) and thermochemical water dissociation (cobalt oxide). From the spray coating process, nanocube electrocatalyst spreads uniformly on large scale (≈6.6 × 5.6 cm2) and is applied to alkaline water electrolyzers, stably delivering 600 mA cm−2 current for >100 h. The photovoltaic‐electrochemical (PV‐EC) system, including silicon PV cells, achieves 11.5% solar‐to‐hydrogen (STH) efficiency stably for >100 h.

Enhanced electrochemical performances of SrMoO4/MWCNT-PVP nanocomposites as electrocatalyst for hydrogen evolution reaction

In this work, we have successfully synthesized the cost-effective, abundant in nature and environmentally friendly SrMoO4/MWCNT-PVP by using the co-precipitation technique for hydrogen evolution reaction (HER). Prepared nanocomposites were characterized by XRD, which confirms the formation of tetragonal structure of SrMoO4 and indexed with JCPDS (01-074-3912). Raman spectra confirm the combination of SrMoO4 with carbon composite (verified by D and G band 1.02 ID/IG ratio) and its functional group was further analyzed with the help of FTIR spectra. Synthesized product morphology was characterized by using SEM and TEM images, which confirms formation of well-defined dumb-bell shaped nanostructures with the combination of carbon nanotube and also it further confirms the formation of polycrystalline nature of the material. The elemental composition was analyzed by EDS images, which confirms the occurrence of Sr, Mo, O, and C in an appropriate form with a uniform distribution, respectively. MWCNT in SrMoO4 incorporation led to decrease overpotential of 204 mV and 110 mV/dec Tafel slope of the material, which was examined by the LSV curves and Tafel plot analysis. Electrochemical impedance spectroscopy was also investigated, and it delivered the small charge-transfer resistance of 248 Ω, which further supporting the HER analysis and denoting the promising HER kinetics. Therefore, our work unlocks a new path for the properly tuned nanostructured morphology of metal oxide with carbon composite for electrochemical hydrogen evolution reaction application.

A Highly Active Porous Mo2C-Mo2N Heterostructure on Carbon Nanowalls/Diamond for a High-Current Hydrogen Evolution Reaction

Developing non-precious metal-based electrocatalysts operating in high-current densities is highly demanded for the industry-level electrochemical hydrogen evolution reaction (HER). Here, we report the facile preparation of binder-free Mo2C-Mo2N heterostructures on carbon nanowalls/diamond (CNWs/D) via ultrasonic soaking followed by an annealing treatment. The experimental investigations and density functional theory calculations reveal the downshift of the d-band center caused by the heterojunction between Mo2C/Mo2N triggering highly active interfacial sites with a nearly zero ∆GH* value. Furthermore, the 3D-networked CNWs/D, as the current collector, features high electrical conductivity and large surface area, greatly boosting the electron transfer rate of HER occurring on the interfacial sites of Mo2C-Mo2N. Consequently, the self-supporting Mo2C-Mo2N@CNWs/D exhibits significantly low overpotentials of 137.8 and 194.4 mV at high current densities of 500 and 1000 mA/cm2, respectively, in an alkaline solution, which far surpass the benchmark Pt/C (228.5 and 359.3 mV) and are superior to most transition-metal-based materials. This work presents a cost-effective and high-efficiency non-precious metal-based electrocatalyst candidate for the electrochemical hydrogen production industry.

Self-healable, Tolerant Superaerophobic Coating for Improving Electrochemical Hydrogen Production.

Gas-evolving electrodes often suffer from the blocking of catalytic active sites-due to unwanted and unavoidable adhesion of generated gas bubbles, which elevates the overpotential for the electrochemical hydrogen evolution reaction (HER)- by raising the resistance of the electrode. Here, a catalyst-free and self-healable superaerophobic coating having ultra-low bubble adhesion is introduced for achieving significantly depleted overpotentials of 209 and 506mV at both low (50mAcm-2) and high (500mAcm-2) current densities, respectively, compared to a bare nickel-foam electrode. The optimized coating ensured an early detachment of the generated tiny (0.8±0.1mm) gas bubble-and thus, prevented the undesired rise in resistance of the coated electrode. The systematic association of physical (i.e., ionic interactions, H-bonding, etc.) cross-linkage, β-amino ester type covalent cross-linkage and reinforced halloysite nano clay enables the design of such functional material embedded with essential characteristics-including improved mechanical (toughness of 63.7kJm-3, and tensile modulus of 26kPa) property and chemical (extremes of pH (1 and 14), salinity, etc.) stability, rapid (<10min) self-healing ability (even at alkaline condition) and desired bubble-wettability (bubble contact angle of 158.2±0.2°) with ultralow force (4.2±0.4µN) of bubble adhesion.

Mn-doped nickel–cobalt sulfides as bifunctional electrodes for high-performance supercapacitors and electrocatalysts for hydrogen evolution reactions

The development of active electrode materials with dual functions of energy storage and electrocatalyst is important for future energy storage and energy conversion devices. In this work, manganese-doped nickel cobalt sulfide (Mn-NCS) mesoporous microspheres were prepared via a simple two-step solvent-thermal method and the effects of different Mn2+ doping levels on the electrochemical properties and hydrogen evolution reactions (HER) of the prepared samples were investigated. As a supercapacitor electrode material, optimized Mn0.5-NCS had a maximum specific capacitance of 1175 C g−1 at a current density of 1 A/g and remained an outstanding capacitance retention rate of 81 % at a current density of 20 A/g. The asymmetric supercapacitor was assembled with the optimal electrode material as the positive electrode and activated carbon as the negative electrode, and a high energy density of 55.4Wh kg−1 was achieved at a power density of 797 W kg−1. The Mn0.5-NCS exhibited the best HER performance in alkaline electrolyte, shown as the lowest overpotential of 95 mV and the smallest Tafel slope of 71 mV dec−1 at a current density of 10 mA cm−2. Experimental tests and density functional theory (DFT) calculations revealed that manganese preferentially occupies nickel sites and acted as an electron donor in the electrochemical process to realize the electron redistribution, increasing electron density and accelerating charge transfer. The results indicated that manganese-doped nickel–cobalt sulfides have great potential as bifunctional electrode materials for high-performance supercapacitors and HER.

Stilbene-incorporated platinum(II) di-yne electrocatalysts for generating hydrogen from acetic acid

Molecular hydrogen (H2) is a potential alternative to fossil fuels since it is a green energy source with high energy density and non-polluting combustion materials. We present herein the electrochemical properties and hydrogen evolution reaction (HER) ability of two Pt(II) diynes (Pt-Sb-Pt & Sb-Pt-Sb) bearing stilbene unit. Both complexes catalyzed the HER in acidic media. In addition, density functional theory (DFT) calculation was carried out at B3LYP/LANL2DZ level of theory in gas phases as well as in the solvent (DMF) to delineate the possible mechanism of HER. We demonstrated that the studied Pt(II) electrocatalysts shift the reduction potential noticeably. However, no apparent role of photo-switchable stilbene fragment on electrolysis was observed and the presence of ethynyl moiety was necessary for stabilization of the metal center. To the best of our knowledge, this is the first study highlighting the electrocatalytic HER by platina-ynes.

Strategically Designed Pd-Induced Changes in Alkaline Hydrogen Evolution Reaction and Oxygen Evolution Reaction Performances of Electrochemical Water Oxidation by the Galvanically Synthesized MoO2/MoO3 Composite Thin Film.

Electrochemical water oxidation is believed to be an effective pathway to produce clean, carbon-free, and environmentally sustainable green energy. In this work, we report a simple, easy-to-construct, facile, low-cost, and single-step galvanic technique to synthesize a Pd-supported temperature-assisted MoOx thin film nanocomposite for effective water oxidation. The most suitable nanocomposite exhibits very low overpotential at 10 mA/cm2 with smaller Tafel slope values for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes in an alkaline medium. The formation of a metal oxide-metal junction accelerates the growth of more active sites, promoting induced electronic synergism at the MoOx-Pd interface. This endows higher electrical conductivity and faster electron transfer kinetics, thus accelerating the faster water dissociation reaction following the Tafel-Volmer mechanism to boost the HER process in an alkaline medium. The excellent electrochemical HER and OER performances of our electrocatalyst even supersede the accomplishments of the benchmark catalysts Pt/C and RuO2. Moreover, neither of these two catalysts demonstrates both catalytic reactions, i.e., HER and OER at the same time, which have been observed for our synthesized catalyst. Our findings illustrate the potential of a thin-film MoOx-Pd nanocomposite to be an exceedingly effective electrocatalyst developed by interface engineering strategies. This also provides insight into designing several other semiconductor composite catalysts using simple synthesis techniques for highly efficient HER/OER processes that could be alternatives to benchmark electrocatalysts for water electrolysis.

Efficient electrochemical hydrogen evolution activity of nanostructured Ag3PO4/MoS2 heterogeneous composite catalyst

Hydrogen (H2) generation by electrochemical water splitting is a key technique for sustainable energy applications. Two-dimensional (2D) transition-metal dichalcogenide (MoS2) and silver phosphate (Ag3PO4) possess excellent electrochemical hydrogen evolution reaction (HER) properties when they are combined together as a composite rather than individuals. Reports examining the HER activity by using Ag3PO4, especially, in combination with the 2D layered MoS2 are limited in literature. The weight fraction of MoS2 in Ag3PO4 is optimized for 1, 3, and 5 wt%. The Ag3PO4/1 wt % MoS2 combination exhibits enhanced HER activity with least overpotential of 235 mV among the other samples in the acidic medium. The synergistic effect of optimal nano-scale 2D layered MoS2 structure and Ag3PO4 is essential for creating higher electrochemical active surface area of 217 mF/cm2, and hence this leads to faster reaction kinetics in the HER. This work suggests the advantages of Ag3PO4/1 wt % MoS2 heterogeneous composite catalyst for electrochemical analysis and HER indicating lower resistivity and low Tafel slope value (179 mV/dec) among the prepared catalysts making it a promising candidate for its use in practical energy applications.