Active Hydrogen Evolution Reaction Catalysts Research Articles

Molybdenum, tungsten doped cobalt phosphides as efficient catalysts for coproduction of hydrogen and formate by glycerol electrolysis

H2 and formate are important energy carriers in fuel-cells and feedstocks in chemical industry. The hydrogen evolution reaction (HER) coupling with electro-oxidative cleavage of thermodynamically favorable polyols is a promising way to coproduce H2 and formate via electrochemical means, highly active catalysts for HER and electrooxidative cleavage of polycols are the key to achieve such a goal. Herein, molybdenum (Mo), tungsten (W) doped cobalt phosphides (Co2P) deposited onto nickel foam (NF) substrate, denoted as Mo-Co2P/NF and W-Co2P/NF, respectively, were investigated as catalytic electrodes for HER and electrochemical glycerol oxidation reaction (GOR) to yield H2 and formate. The W-Co2P/NF electrode exhibited low overpotential (η) of 113 mV to attain a current density (J) of −100 mA cm−2 for HER, while the Mo-Co2P/NF electrode demonstrated high GOR efficiency for selective production of formate. In situ Raman and infrared spectroscopic characterizations revealed that the evolved CoO2 from Co2P is the genuine catalytic sites for GOR. The asymmetric electrolyzer based on W-Co2P/NF cathode and Mo-Co2P/NF anode delivered a J = 100 mA cm−2 at 1.8 V voltage for glycerol electrolysis, which led to 18.2 % reduced electricity consumption relative to water electrolysis. This work highlights the potential of heteroelement doped phosphide in catalytic performances for HER and GOR, and opens up new avenue to coproduce more widespread commodity chemicals via gentle and sustainable electrocatalytic means.

High Surface Area MoS2 and WS2 As Active HER Catalysts

The ever-increasing demand for clean energy necessitates a widespread adoption of clean energy carriers, namely green hydrogen. However, its production via electrolysis remains expensive. To achieve the needed drop in production cost, efficient catalyst materials are sought after to overcome the energy barrier of water splitting. Transition metal dichalcogenides (TMDCs) such as tungsten and molybdenum disulfide (WS2, MoS2) have been identified as promising catalysts because of their remarkably low Gibbs free energy for hydrogen adsorption.[1] The main challenge for these materials is the precise fabrication of continuous (mono)layers to achieve the desired functional properties.[2] Bottom-up material fabrication approaches like the vapor phase methods CVD and ALD offer several advantages. The use of chemical reactions of gas phase species allows precise thickness control, high quality films and allow large areas to be coated.This study focused on the fabrication of WS2 and MoS2 layers via metal organic chemical vapor deposition (MOCVD) and subsequent investigation of the properties of the resulting films in relation to the applied process conditions. Depositions were performed on FTO substrates and their thickness dependent capability to catalyze the electrochemical hydrogen evolution reaction (HER) were investigated in detail.For WS2 the selective growth of the semiconducting hexagonal phase with the targeted stoichiometry at a deposition temperature of 600°C was achieved (Fig 1 a). Similarly, in the case of MoS2, the hexagonal phase could be selectively deposited from 400 °C onwards and with pronounced crystallinity at 600°C (Fig. 1 b) which also showed the best stochiometric match and highest purity. The thin film characterization was further supported by Raman spectroscopy which serves as probe to verify the formed phase and layer number for 2D-materials. UV-VIS spectroscopy was employed to assess the semiconducting behavior allowing for band gap determination via the Tauc plot. Morphology and surface topography, especially interesting in the realm of HER catalysis, were assessed by SEM and HR-TEM showing the typical flakelike features known for these materials in their hexagonal phase (Fig 1 c). Electrochemical LSV experiments of WS2 in H2SO4 showed thickness dependence of the overpotentials which correlates with the flake density and the availability of vertical edge sites most active for HER (Fig 1 d). Similar studies for MoS2 are ongoing. These results are especially noteworthy as previous studies on WS2 deposited onto FTO have reported notably higher overpotentials.[3,4] This study demonstrates the potential of large area and high surface area TMDCs as effective HER electrocatalysts.[1] S. H. Noh, J. Hwang, J. Kang, M. H. Seo, D. Choi, B. Han, J. Mater. Chem. A 2018, 6, 20005–20014.[2] K. S. Novoselov, D. Jiang, A. K. Geim, et al. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 10451–10453.[3] J.-L. Wree, J.-P. Glauber, A. Devi, et al. J. Mater. Chem. C 2021, 9, 10254–10265.[4] J.-L. Wree, E. Ciftyurek, A. Devi, et al. Dalton Trans. 2020, 49, 13462–13474. Figure 1

(Invited) Development of Sustainable Electrocatalysts for Anion Exchange Membrane Fuel Cells and Electrolyzers

The electrocatalytic hydrogen oxidation (HOR) and evolution (HER) reactions under alkaline conditions are kinetically slow processes even when Pt group metals are employed. This presentation discusses our strategies to improve the activity of non platinum catalysts. For example, to improve the alkaline HOR activity of transition metal nanoparticles we look at engineering strong interactions with metal oxides incorporated with carbon-based catalyst supports.(1,2) Another strategy involves utilizing novel carbon materials such as onion like carbon (OLC). We have shown that the combination of CeO2 and OLC in Pd–CeO2/OLC induces surface defects and modifies the electronic structure of the Pd-OLC interface, significantly improving electrical conductivity due to enhanced charge redistribution. Such results were corroborated by density functional theory (DFT) calculations.(3) Using this strategy, peak power densities of up to 2 W cm-2 have been achieved when Pd-CeO2 is incorporated in AEMFCs.(4) Regarding the alkaline HER, mixed phase Ni-Mo and MoO3-x materials are known to have enhanced alkaline hydrogen evolution reaction (HER) activity. Here we describe the optimization of the preparation of an active HER catalyst composed of MoO2 surface nanorod arrays on nickel foam (see Figure). Large circular cathode electrodes (Area 80 cm2) were prepared and tested in a three cell stack AEM electrolyser.(5) M. V. Pagliaro, C. L. Wen, B. Sa, B. Y. Liu, M. Bellini, F. Bartoli, S. Sahoo, R. K. Singh, S. P. Alpay, H. A. Miller and D. R. Dekel, ACS Catal., 10894 (2022).M. V. Pagliaro, M. Bellini, F. Bartoli, J. Filippi, A. Marchionni, C. Castello, W. Oberhauser, L. Poggini, B. Cortigiani, L. Capozzoli, A. Lavacchi, H. A. Miller and F. Vizza, Inorg. Chim. Acta, 543 (2022).J. Ogada, A. K. Ipadeola, P. V. Mwonga, A. B. Haruna, F. Nichols, S. W. Chen, H. A. Miller, M. V. Pagliaro, F. Vizza, J. R. Varcoe, D. M. Meira, D. M. Wamwangi and K. I. Ozoemena, ACS Catal., 12, 10938 (2022).H. A. Miller, M. Bellini, D. R. Dekel, and F. Vizza, Electrochemistry Communications, 135, 107219 (2022).F. Bartoli, L. Capozzoli, T. Peruzzolo, M. Marelli, C. Evangelisti, k. Bouzek, J. Hnat, G. Serrano, L. Poggini, K. Stojanovski, V. Briega-Martos, S. Cherevko, H. A. Miller and F. Vizza, J. Mater. Chem. A, 11, 5789 (2023). Figure 1

Machine learning assisted screening of doped metals phosphides electrocatalyst towards efficient hydrogen evolution reaction

Transition metals (TM) doped metal phosphides usually exhibits promising reactivity towards acidic hydrogen evolution reaction (HER). However, the experimental screening of highly active TM-doped metal phosphides catalyst is time-consuming and challenging. In this study, a density functional theory combined machine learning (DFT-ML) framework is proposed to accelerate the screening and predicting TM-doped metal phosphides-based HER electrocatalysts. In this framework, the ML database is constructed using critical catalyst features and DFT-calculated adsorption energy of HER intermediates. Also, local average electronegativity of the adsorption site and the surrounding atoms as catalyst feature is proposed to describe the reaction sites in this ML model. Using the HER energetics on the state-of-art highly active Pt (111) as benchmark catalyst model, a set of 10 potential active HER catalysts is predicted. By performing the H* adsorption Gibbs free energy change analysis on these ML-predicted catalysts, six promising TM-doped metal phosphides HER catalysts are determined in the sample space. This study provides a facile and effective approach for the quick screening of high-performance HER electrocatalysts.

Reductive chemistry of pyrrolic macrocycles: A PCET dichotomy between metal and ligand

Proton-coupled electron transfer (PCET) is central to the reactivity of porphyrins. The coupling of the electron to the proton is central to a porphyrin’s ability to catalyze energy conversion reactions of which the hydrogen evolution reaction (HER) is exemplary. To understand the mechanistic details of the PCET chemistry of porphyrins and related macrocyclic congeners, we have designed hangman constructs that allow a proton, placed in the secondary coordination sphere (off of the hangman backbone), to be coupled to redox transformations at the macrocycle. For metals whose reduction potentials are positive of the porphyrin macrocycle, such as Co and Fe, HER catalysis is confined to PCET transformations of the metal center where the active catalyst for HER is a reduced metal hydride. Alternatively, the reduction potentials of Ni, Zn, and 2H (freebase) porphyrins allow for redox non-innocence of the macrocycle; here the active “hydridic” catalyst is a phlorin, which gives rise to elaborate HER reaction sequences. Beyond HER catalysis, redox non-innocence of Ni, Zn, and 2H porphyrins and related compounds has been informative for providing detailed mechanistic insight into the multi-site PCET hydrogenation of olefinic bonds of the macrocycle. This mini-review unravels the PCET dichotomy between the metal and macrocycle in promoting HER catalysis and novel chemical transformations that give rise to unusual macrocyclic structures.

Electrocatalysts based on MoS2 and WS2 for hydrogen evolution reaction: An overview

AbstractRecently, hydrogen energy has been significantly investigated by numerous technologies. To date, noble platinum group metals have often been employed to fabricate working electrodes for hydrogen evolution reaction (HER). Therefore, the demand of highly active HER catalysts based on effective and lower‐cost materials is becoming more and more critical. Transition metal dichalcogenide (TMD) materials could be one of the most suitable materials for these requirements because they possess numerous unique mechanical, electronic, and chemical characteristics that are greatly beneficial for HER processes. Among many TMD materials, tungsten disulfide (WS2) and molybdenum disulfide (MoS2) are the most well‐known TMD materials which have been intensively studied for different applications, including HER, batteries, and supercapacitors. In this review, we tried to cover the HER mechanism of catalysts and their parameters. Besides that, the structures, properties, preparation, and HER performance of catalyst materials based on WS2 and MoS2 are comprehensively discussed. After that, the challenges and future trends of catalysts based on WS2 and MoS2 for HER are also considered.

Palladium nanoparticles confined in uncoordinated amine groups of metal-organic frameworks as efficient hydrogen evolution electrocatalysts.

Hydrogen obtained through the electrolysis of water is a potential solution to the growing demand of human society for energy. In addition, water electrolysis generates less environmental pollution than fossil energy sources. However, the preparation of highly active and low-cost electrocatalysts remains a key challenge. Here, we report a facile and inexpensive method to prepare palladium nanoparticles (Pd NPs) supported on aminated (-NH2) metal-organic frameworks (MOF). The obtained electrocatalyst (Pd@Uio-66-NH2) exhibits excellent electrocatalytic performance for the hydrogen evolution reaction (HER), featuring an ultralow overpotential (34 mV at 10 mA cm-2), small Tafel slope (41 mV dec-1), and superior stability in acid electrolyte. Systematic characterization demonstrated that -NH2 can effectively stabilize palladium acetate as the Lewis base. Meanwhile, the strong interaction between the lone pair electrons and the d-orbital ensures that the Pd atoms are uniformly distributed in the MOF material, inhibiting the agglomeration of metal NPs in the reaction. This strategy provides an avenue to prepare inexpensive and highly active catalysts for HER in acidic media.

Structurally Modified MXenes-Based Catalysts for Application in Hydrogen Evolution Reaction: A Review

Green hydrogen production via electrocatalytic water splitting paves the way for renewable, clean, and sustainable hydrogen (H2) generation. H2 gas is produced from the cathodic hydrogen evolution reaction (HER), where the reaction is catalyzed primarily from Pt-based catalysts under both acidic and alkaline environments. Lowering the loading of Pt and the search for alternative active catalysts for HER is still an ongoing challenge. Two-dimensional MXenes are effective supports to stabilize and homogenously distribute HER-active electrocatalysts to boost the HER performance. Factors involved in the effectiveness of MXenes for their role in HER include transition metal types and termination groups. Recently, tailoring the conditions during the synthesis of MXenes has made it possible to tune the morphology of MXenes from multilayers to few layers (delaminated), formation of porous MXenes, and those with unique crumpled and rolled structures. Changing the morphology of MXenes alters the surface area, exposed active sites and accessibility of electrolyte materials/ions to these active sites. This review provides insight into the effects of varying morphology of MXenes towards the electrocatalytic HER activity of the MXene itself and MXene composites/hybrids with HER-active catalysts. Synthesis methods to obtain the different MXene morphologies are also summarized.

Rational Designing of Bimetallic/Trimetallic Hydrogen Evolution Reaction Catalysts Using Supervised Machine Learning.

Cost-efficient electrocatalysts to replace precious platinum group metals- (PGMs-) based catalysts for the hydrogen evolution reaction (HER) carry significant potential for sustainable energy solutions. Machine learning (ML) methods have provided new avenues for intelligent screening and predicting efficient heterogeneous catalysts in recent years. We coalesce density functional theory (DFT) and supervised ML methods to discover earth-abundant active heterogeneous NiCoCu-based HER catalysts. An intuitive generalized microstructure model was designed to study the adsorbate's surface coverage and generate input features for the ML process. The study utilizes optimized eXtreme Gradient Boost Regression (XGBR) models to screen NiCoCu alloy-based catalysts for HER. We show that the most active HER catalysts can be screened from an extensive set of catalysts with this approach. Therefore, our approach can provide an efficient way to discover novel heterogeneous catalysts for various electrochemical reactions.

Mechanically processing copper plate into active catalyst for electrochemical hydrogen production

As a cheap and earth-abundant metal, copper is known highly conductive but inactive for catalyzing hydrogen evolution reaction (HER) due to its fully filled d orbital and weak adsorption for hydrogen intermediate. Herein, we adopt a mechanical stirring process to introduce a large number of dislocations into copper plate, and retain the dislocations by the quenching effect of dry ice. Theoretical computation indicates that dislocation can cause uneven distribution of charge density, and the electron-deficient area remarkably enhances the hydrogen adsorption, turning inactive copper into active HER catalyst. The product achieves high turnover frequency, low overpotential and long-term durability. Our work bridges mechanical process and functional materials, and exploits a powerful technology on producing self-supported catalysts in a rapid way

Facile Spray Pyrolysis Synthesis of Ruthenium Single-Atomic Catalyst with High Activity and Stability for Hydrogen Evolution Reactions over a Wide pH Range

Electrochemical water splitting is an economic, green and sustainable route to produce hydrogen through the hydrogen evolution reaction (HER). Nowadays, ruthenium is an efficient catalyst with a desirable cost for HER. Doping Ru with a transition metal oxide was recently shown to greatly boost the activity and durability of the HER, even with small amounts of ruthenium based electrocatalysts. It also reduced total amount of Ru. Recent literature reported that Ru-O-Mo sites have better HER than Ru single atom due to significantly improved H2O adsorption. Among the various synthetic method, spray pyrolysis methods can produce rapidly large-scale production of uniformly mixed elements in spherical particles at one-step. In this study, we synthesized ruthenium doped MoO2 spheres (200~300nm) using ultrasonic spray pyrolysis method in various temperature from 500 oC to 800 oC. The synthesized catalysts were analyzed by XRD, FE-SEM, Raman, XPS and electrochemical analyzer. This research can provide a new strategy to synthesize highly active catalysts for HER over a wide pH range.

Dynamic Co(µ‐O)2Ru Moiety Endowed Efficiently Catalytic Hydrogen Evolution

AbstractA large number of highly active Ru‐based electrocatalysts have been reported for the hydrogen evolution reaction (HER). The utilization of synergistic effects for promoting HER performance remains inadequate, especially for corresponding potential‐driven reactive sites at the atomic level. Herein, a Co‐substituted RuRu2P structure is employed as a model system to reveal the synergistic effect on Ru‐based electrocatalysts and to realize the potential‐driven reactive sites during the HER. Optimized RuRu2P @ Co0.6 exhibits a superior catalytic performance in alkaline electrolytes, achieving a low overpotential of 9 mV at a current density of 10 mA cm–2. To precisely describe the geometrical nature of surface moiety of Co(µ‐O)2Ru, an indicator (β) is established to quantify the strain of Co(µ‐O)2Ru moieties through calculating the LCoL (L = P or O) angles through employing in situ X‐ray absorption spectroscopy. Both bond strain and corresponding metal‐metal distance of CoRu in Co(µ‐O)2Ru moiety can significantly affect the structural tolerance and facilitate the coupling of adsorbed hydrogen atoms during HER. It is believed that the perspective raised in the present work will provide a new avenue to the design of highly active HER catalysts at the atomic scale.

Hydrogen evolution reaction activity of III-V heterostructure nanowires

III-V materials have gained great interest in materials science community since a few decades due to their versatile properties. Experimenting with the crystal phase, dimensional confinement, chemical environment and external conditions open-up a window to finely tune the properties of material of interest at atomic scale. The density functional theory-based investigation of III-V semiconductors under heterostructure nanowire configuration is presented with specific focus on the electronic dispersion and band alignment. The combination of GaSb core having triangular(T)/circular(R) cross-sections with GaP and GaAs shells reveal formation of type-II heterostructure with moderate electronic band gap suggesting promising application in photocatalysis and photovoltaics. Motivated by these results, we have investigated the catalytic activity of the heterostructure nanowires towards hydrogen evolution reaction (HER). Interesting results showing reliable HER activity over different surface sites of the nanowires evidently approve their importance as an active HER catalyst. Furthermore, being within nano regime, the present systems suggest cost-effective production of HER catalyst as compared to the conventional novel metal-based catalysts.

Phosphatizing Engineering of Perovskite Oxide Nanofibers for Hydrogen Evolution Reaction to Achieve Extraordinary Electrocatalytic Performance

AbstractPerovskite oxides with tailored elements and structures endow promising electrocatalytic properties for hydrogen evolution reaction (HER) due to considerable activity and satisfactory long‐term operating stability. However, the synthesis of 1D perovskite nanostructures with anion dopants remains a challenge, as well as insights into the performance origin from experimental and theoretical views. Herein, combined with electrospinning and phosphatizing strategies, P‐doped Pr0.5La0.5BaCo2O5+δ perovskite nanofibers (P‐PLBC‐F) are reported for highly active HER catalysts. The P‐PLBC‐F catalyst outperforms the classic perovskites and can be comparable to the commercial Pt/C (wtPt = 20%) benchmark, exhibiting a Tafel slope of −32.9 mV dec−1 and overpotential of −307 mV at 500 mA cm−2 disk in alkaline media. The highly catalytic activity benefits from the desired 1D nanostructure, steered electronic structures (charge transfer energy ΔCo‐P = 0.79 eV) and Gibbs free energy for the H* desorption (1.02 eV) induced by the P3− doping, as supported by density functional theory calculations. The findings described here unveil the phosphatizing mechanism of the perovskites for catalyzing the hydrogen production, and broaden horizons in terms of rational designs of novel perovskite‐based catalysts for sustainable energy.

Design of nanocatalyst for electrode structure: Electrophoretic deposition of iron phosphide nanoparticles to produce a highly active hydrogen evolution reaction catalyst

• FeP NP electrocatalytic electrode was fabricated via electrophoretic deposition. • Morphology and porosity of catalyst layer were tuned by altering deposition kinetics. • Optimized porosity/catalyst loading lead to the excellent HER activity. • The HER electrode was successfully applied as cathode GDE of high performance PEMWE. The inherent properties of nanoparticles (NPs) can be engineered into macroscopic structures by capturing the collective characteristics of the nanomaterials via a fabrication process to realize macroscopic functionality. Herein, we report a powerful manufacturing technique for fabricating an electrode composed of highly porous iron phosphide (FeP) NP catalyst layers conformally deposited on macroporous Carbon paper (CP) that shows excellent hydrogen evolution reaction activity. The surface morphology and porosity of the FeP NP catalyst layers on the FeP/CP electrode were tuned by altering the deposition kinetics of the colloidal FeP NPs by controlling the solvent system in the electrophoretic deposition process. The FeP/CP electrode achieved a low overpotential of 38 mV at 10 mA cm −2 in 0.5 M H 2 SO 4 due to the highly exposed catalytic surface with a high catalyst loading amount and fast charge transfer. When the FeP/CP electrode was applied as a cathode gas diffusion electrode in a proton exchange membrane water electrolyzer, the single-cell exhibited excellent operating performance (1.48 A cm −2 @ 2.0 V cell , 90 °C). Our results illustrate a facile route for fabricating nanostructured macroscale devices by maximizing the collective properties of the nanoscale materials.

Amorphous CoFeB on nickel foam as a high efficient electrocatalyst for hydrogen evolution reaction

The development of high-performance, low cost and earth abundant catalysts for hydrogen evolution reaction (HER) is desired. This work presents amorphous CoFeB supported on nickel foam (NF), prepared by a facial chemical reduction method, as an active catalyst for HER in alkaline solution. Structure characterization indicated that with the incorporation of Fe atom, CoFeB catalysts exhibit similar petal-like granular morphology as CoB. The optimal CoFeB/NF-0.15 catalyst exhibits Brunauer-Emmett-Teller (BET) surface area of 27.4 m2 g−1, nearly two times larger than 13.2 m2 g−1 for CoB, suggesting higher specific surface area. CoFeB/NF-0.15 catalyst shows excellent HER performance and reaches −10 mA cm−2 at overpotential of 35 mV in alkaline solution, and Tafel slope of 84.7 mV dec−1, indicative of Volmer-Heyrovsky reaction mechanism. The synergistic effect among Fe, Co and B atoms and the more exposed active sites as well as faster electron transfer kinetics collectively contributed to the improved intrinsic activity of CoFeB for HER. Moreover, CoFeB/NF-0.15 exhibits good stability for over 16 h.

In situ electrochemical dehydrogenation of ultrathin Co(OH)2 nanosheets for enhanced hydrogen evolution

Transition metal hydroxides/oxyhydroxides have recently emerged as highly active electrocatalysts for oxygen evolution reaction in alkaline water electrolysis, while have not yet been widely investigated for hydrogen evolution electrocatalysts owing to their unfavorable H*-adsorption, making it difficult to construct an overall-water-splitting cell for hydrogen production. In this work, we proposed a straightforward and effective approach to develop an efficient in-plane heterostructured CoOOH/Co(OH)2 catalyst via in-situ electrochemical dehydrogenation method, in which the dehydrogenated –CoOOH and Co(OH)2 at the surface synergistically boost the hydrogen evolution reaction (HER) kinetics in base as confirmed by high-resolution transmission electron microscope, synchrotron X-ray absorption spectroscopy, and electron energy loss spectroscopy. Due to the in-situ dehydrogenation of ultrathin Co(OH)2 nanosheets, the catalytic activity of the CoOOH/Co(OH)2 heterostructures is progressively improved, which exhibit outstanding hydrogen-evolving activity in base requiring a low overpotential of 132 mV to afford 10 mA/cm2 with very fast reaction kinetics after 60 h dehydrogenation. The gradually improved catalytic performance for the CoOOH/Co(OH)2 is probably due to the enhanced H*-adsorption induced by the synergistic effect of heterostructures and better conductivity of CoOOH relative to electrically insulating Co(OH)2. This work will open the opportunity for a new family of transition metal hydroxides/oxyhydroxides as active HER catalysts, and also highlight the importance of using in situ techniques to construct precious metal-free efficient catalysts for alkaline hydrogen evolution.

A new hyperbranched water-splitting technique based on Co3O4/MoS2 nano composite catalyst for High-Performance of hydrogen evolution reaction

Due to the extensive use of fossil fuels & their direct influence on the environment, new ways of producing energy sources are highly needed. Hydrogen is the perfect candidate for renewable energy; however, H2 gas production is associated with disadvantages due to a lack of efficient and active catalysts that could be cost-effective and comparable to platinum performance. Active hydrogen evolution reaction catalysts are needed to advance the development of a cheaper generation of solar fuels. Thus, outperformance, and stable earth abundant. And inexpensive catalysts are highly demanded. That is H2 gas production from the electrolysis of water through HER. In this work, we present different analytical techniques that characterize an efficient and highly stable catalyst based on transition metal oxide Co3O4/MoS2 nanostructures. And their composites for water splitting in harsh acidic conditions time and material chemical composition as like SEM, EDS, XRD, HRTEM & XPS. The composite material is highly best to produce HER at 10 mA cm−2 and obtained 268 mV overpotential of nano Co3O4/MoS2 (S3) and Tafel slope of 56 mv/dec. Faraday efficiencies of the hydrogen gas production measured for the 60 min and catalyst is highly durable for the 20 h. The presented catalysts are up to the mark of platinum metal performance and superior to several transition metal oxides. This fabrication technology is a new roadmap for developing active and scalable hydrogen-evolving catalysts by overcoming the issues of fewer catalytic edges, low density, and poor conductivity.

Dual Doping of MoP with M(Mn,Fe) and S to Achieve High Hydrogen Evolution Reaction Activity in Both Acidic and Alkaline Media

AbstractRational design of cost‐effective, high performance and stable hydrogen evolution reaction (HER) electrocatalysts in both acidic and alkaline media holds the key to the future hydrogen‐based economy. Herein, we introduce an effective approach of simultaneous non‐metal (S) and metal (Fe or Mn) doping of MoP to achieve excellent HER performance at different pH. The catalysts show remarkable overpotentials at −10 mA cm−2 of only 65 and 68 mV in 0.5 M H2SO4, and 50 and 51 mV in 1.0 M KOH, respectively, as well as much higher turnover frequencies compared to undoped MoP. Furthermore, the catalysts exhibit outstanding long‐term stability at a fixed current of −10 mA cm−2 for 40 h. The effects of both dopants, such as electronic structure modification and enhancement of the intrinsic activity, increase of the electrochemically active surface area, and formation of coordinatively unsaturated edge sites, act cooperatively to accelerate the HER at both pH media. Additionally, the presence of oxophilic Mn and Fe at the surface results in Mn or Fe oxide/hydroxide species that promote the dissociation of water molecules in alkaline electrolyte. This work introduces a facile and effective design principle that could pave the way towards engineering highly active HER catalysts for a wide pH range.

Nanoscaled and Atomic Ruthenium Electrocatalysts Confined Inside Super-Hydrophilic Carbon Nanofibers for Efficient Hydrogen Evolution Reaction.

A series of Ru-based catalysts have been developed for the hydrogen evolution reaction (HER) by the facile impregnation of copious and eco-friendly bacterial cellulose (BC) with Ru(bpy)3 Cl2 (bpy = 2,2'-bipyridine) followed by pyrolysis. After the oxidation and molecular recomposition processes that occur within the BC precursors during pyrolysis, sub-2nm Ru nanoparticles (NPs) and atomic Ru species confined within surface-oxidized N-doped carbon nanofibers (CNFs) can be observed in the derived catalysts. The surface oxidation of CNFs leads the derived catalysts with super hydrophilicity and water-absorbing capacity, and also provides dimensional confinement for the nanoscaled and atomic Ru species. With these added structural advantages and the component synergy, the derived catalysts show superior HER activities, for which the overpotentials are as low as 19.6mV (1 m KOH) and 55.0mV (0.5 m H2 SO4 ) for the most active case at the current density of 10mA cm-2 . Moreover, superior HER activity can be also achieved for the catalysts derived with a wide range of Ru loadings. Finally, the influence of Ru NP size on HER activity is investigated by density functional theory simulations. This method provides a reliable protocol for preparing highly active HER catalysts for scale-up applications.