Sulfur-Decorated Molybdenum Carbide Catalysts for Enhanced Hydrogen Evolution

One Stone, Three-Birds Approach: Ultra-active Ru/N, S-MoO2/CNTs Electrocatalyst for Overall Water Splitting in Wide Electrode Applications (NF, GC, and CC)

The construction of exceptionally multifunctional electrocatalysts is essential for various applications, but it poses significant challenges. A novel electrocatalyst, denoted as Ru/N, S-MoO2/CNTs, was successfully synthesized using a combination of mechano-grinding and hydrothermal/calcination techniques. The Ru/N, S-MoO2/CNTs demonstrates ultrasmall overpotentials of 12 and 163 mV in NF, 51 and 167 mV in GCE, and 54 and 173 mV in CC for HER and OER, respectively, at a current density of 10 mA/cm2 in alkaline medium. To accomplish electrocatalytic OWS, a current density of 10 mA/cm2 can be obtained by using a cell voltage of 1.446 V. Theoretical studies demonstrated that the inclusion of Ru, N, and S triggers a change in the composition of MoO2; produces oxygen vacancies; and forms Ru, N, and S-oxygen-Mo catalytic centers. The combination of Ru, N, and S nanoclusters; Ru, N, and S-oxygen-Mo catalytic centers; and OVs-enriched MoO2 would position it among the top electrocatalysts.

In Operando X-ray Spectroscopic and DFT Studies Revealing Improved H2 Evolution by the Synergistic Ni-Co Electron Effect in the Alkaline Condition

The different electrolyte conditions, e.g., pH value, for driving efficient HER and OER are one of the major issues hindering the aim for electrocatalytic water splitting in a high efficiency. In this regard, seeking durable and active HER electrocatalysts to align the alkaline conditions of the OER is a promising solution. However, the success in this strategy will depend on a fundamental understanding about the HER mechanism at the atomic scale. In this work, we have provided thorough understanding for the electrochemical HER mechanisms in KOH over Ni- and Co-based hollow pyrite microspheres by in operando X-ray spectroscopies and DFT calculations, including NiS2, CoS2, and Ni0.5Co0.5S2. We discovered that the Ni sites in hollow NiS2 microspheres were very stable and inert, while the Co sites in hollow CoS2 microspheres underwent reduction and generated Co metallic crystal domains under HER. The generation of Co metallic sites would further deactivate H2 evolution due to the large hydrogen desorption free energy (-1.73 eV). In contrast, the neighboring Ni and Co sites in hollow Ni0.5Co0.5S2 microspheres exhibited the electronic interaction to elevate the reactivity of Ni and facilitate the stability of Co without structure or surface degradation. The energy barrier in H2O adsorption/dissociation was only 0.73 eV, followed by 0.06 eV for hydrogen desorption over the Ni0.5Co0.5S2 surface, revealing Ni0.5Co0.5S2 as a HER electrocatalyst with higher durability and activity than NiS2 and CoS2 in the alkaline medium due to the synergy of neighboring Ni and Co sites. We believe that the findings in our work offer a guidance toward future catalyst design.

Heterostructures coupling ultrathin metal carbides and chalcogenides

Non-layered transition metal carbides (TMCs) and layered transition metal dichalcogenides (TMDs) are two well-studied material families that have individually received considerable attention over the past century. In recent years, with the shift towards two-dimensional materials and heterostructures, a field has emerged that is focused on the structure and properties of TMC/TMD heterostructures, which through chemical conversion exhibit diverse types of heterostructure configuration that host coupled 2D-3D interfaces, giving rise to exotic properties. In this Review, we highlight experimental and computational efforts to understand the routes to fabricate TMC/TMD heterostructures. Furthermore, we showcase how controlling these heterostructures can lead to emergent electronic transport, optical properties and improved catalytic properties.

Tiny Ni3S2 boosting MoS2 hydrogen evolution in alkali by enlarging coupling boundaries and stimulating basal plane

The relatively slow reaction kinetics of the hydrogen evolution reaction (HER) by water electrolysis in alkali hinder its large-scale industrial production. To improve the HER activity in alkaline media, a novel Ni₃S₂/MoS₂/CC catalytic electrode was synthesized by a simple two-step hydrothermal method in this work. The modification of MoS₂ by Ni₃S₂ could facilitate the adsorption and dissociation of water, thus accelerating the alkaline HER kinetics. Moreover, the unique morphology of small Ni₃S₂ nanoparticles grown on MoS₂ nanosheets not only increased the interface coupling boundaries, which acted as the most efficient active sites for the Volmer step in alkaline medium, but also sufficiently activated the MoS₂ basal plane, thus providing more active sites. Consequently, Ni₃S₂/MoS₂/CC only needed overpotentials of 189.4 and 240 mV to drive current densities of 100 and 300 mA·cm^-2, respectively. More importantly, its catalytic performance of Ni₃S₂/MoS₂/CC even exceeded that of Pt/C at a high current density after 261.7 mA·cm^-2 in 1.0 M KOH.

Co3O4-MoSe2@C nanocomposite as a multi-functional catalyst for electrochemical water splitting and lithium-oxygen battery

Co₃O₄-MoSe₂@C nanocomposite has been prepared by a convenient method via combining hydrothermally synthesized MoSe₂@C and Co₃O₄. When catalyzing the hydrogen evolution reaction and oxygen evolution reaction, the catalyst features low overpotentials of 144 mV and 360 mV (both at 10 mA cm^-2current density), respectively. It can also serve as the cathode in the lithium-oxygen battery and the device shows a low charging-discharging overpotential of 1.50 V with a stable performance of over 200 cycles at current density of 1000 mA g^-1, shedding light on the design and synthesis of novel multifunctional electrocatalysts for energy conversions.

3D Hierarchical Porous Fe/Ni-P-B as Practical Bifunctional Electrode for Alkaline Water Electrolysis

Bifunctional electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are extremely attractive as they can simplify the water electrolysis system. Here, a general and scalable strategy to prepare stable and efficient bifunctional electrode was reported, based on a novel hierarchical porous structure constructed by conductive electrocatalyst. The method involved the construction of 3D monolithic structure and its surface reconstruction by chemical etching process. This strategy produced an advanced 3D hierarchical porous Fe/Ni-P-B@MS electrode containing well-defined macropores (>100 μm) at the inter-wire space and mesopores (<100 nm) distributed uniformly over the entire catalyst surface. This highly efficient bifunctional electrode required only 79 and 279 mV to reach 100 mA cm^-2 toward HER and OER in 1.0 m KOH. An alkaline electrolyzer consisting of this electrode provided 100 mA cm^-2 at a low cell voltage of 1.61 V and survived at large current density of 800 mA cm^-2 for over 140 h without apparent degradation. This work provides a new perspective for the rational design of transition metal-based bifunctional electrodes with outstanding performance.

Supramolecular confinement pyrolysis to carbon-supported Mo nanostructures spanning four scales for hydroquinone determination

Metal nanostructures with high atom utilization, abundant active sites, and special electron structures should be beneficial to the electrochemical monitoring of hydroquinone (HQ), a highly toxic environmental pollutant. However, traditional nanostructures, especially non-noble metals generally suffer from severe aggregation, or consist of a mixture of nanoparticles and nanoclusters, resulting in low detection sensitivity. Herein, we precisely control the size of Mo-based nanostructures spanning four scales (viz. Mo₂C nanoparticles, Mo₂C nanodots, Mo nanoclusters and Mo single atoms) anchored on N, P, O co-doped carbon support. The detection sensitivity of four samples toward the HQ follows the orders of Mo single atoms＞Mo₂C nanodots＞Mo nanoclusters＞Mo₂C nanoparticles. The catalytic ability of four catalysts is investigated, also showing the same order. The supported Mo single atoms show superior electro-sensing performance for HQ with wide linear range (0.02-200 μM) and low detection limit (0.005 μM), surpassing most previously reported catalysts. Moreover, the coexistence of dihydroxybenzene isomers of catechol (CC) and resorcinol (RC) does not interfere with the detection of HQ on the Mo single-atom sensor. This work opens up a polyoxometalate-based confinement pyrolysis approach to constructing ultrafine metal-based nanostructures spanning multiple-scales for efficient electrochemical applications.

Smart Designs of Mo Based Electrocatalysts for Hydrogen Evolution Reaction

As a sustainable and clean energy source, hydrogen can be generated by electrolytic water splitting (i.e., a hydrogen evolution reaction, HER). Compared with conventional noble metal catalysts (e.g., Pt), Mo based materials have been deemed as a promising alternative, with a relatively low cost and comparable catalytic performances. In this review, we demonstrate a comprehensive summary of various Mo based materials, such as MoO2, MoS2 and Mo2C. Moreover, state of the art designs of the catalyst structures are presented, to improve the activity and stability for hydrogen evolution, including Mo based carbon composites, heteroatom doping and heterostructure construction. The structure–performance relationships relating to the number of active sites, electron/ion conductivity, H/H2O binding and activation energy, as well as hydrophilicity, are discussed in depth. Finally, conclusive remarks and future works are proposed.

Interface engineering triggered by carbon nanotube-supported multiple sulfides for boosting oxygen evolution

Finding an efficient, stable and cheap oxygen evolution reaction (OER) catalyst is very important for renewable energy conversion systems. There are relatively few related research reports due to the thermodynamic instability of transition metal sulfides (TMSs) at the oxidation potential and these are usually focused on single metal sulfides or bimetal sulfides. Metal sulfide mixture systems are rarely studied. The fabrication of a TMS/TMS interface is a feasible method to improve the kinetics of the OER. Here, we constructed TMS hybrid electrocatalysts with multiple phase interfaces for the oxygen evolution reaction, named S-CoFe/CNTs. The results show that the S-CoFe/CNT catalyst exhibits a low overpotential of 258 mV to achieve a current density of 10 mA cm^-2, and has high activity in the OER process. Meanwhile, the catalyst also shows a low Tafel slope (69 mV dec^-1) and good stability. This can be attributed to the synergistic catalysis of the multiphase interface in the catalyst and the rapid electron transfer pathway brought by CNTs. The new strategy for the synthesis of catalysts containing the TMS/TMS interface provides a new idea and method for the development of efficient and practical water splitting catalysts.

Development of a Ni-Doped VAl3 Topological Semimetal with a Significantly Enhanced HER Catalytic Performance

Topological materials with robust topological surface states appear to be well-suited as electrochemical catalysts. However, few studies have been published on the development of non-noble metal topological catalysts, most likely because the topological properties tend to be attributed to the s and p orbital electrons, while transition-metal catalysis mainly involves d orbital electrons. Herein, we proposed a topological semimetallic (TSM) compound, VAl₃, with a surface state consisting mainly of d orbital electrons, as an electrocatalyst for the hydrogen evolution reaction (HER). Density functional theory (DFT) calculations showed that the surface state electrons enhanced the adsorption of H atoms. Moreover, the transfer of surface state electrons between the surface and adsorbed H atoms was optimized through nickel doping. We experimentally prepared single-crystals VAl₃ and V_0.75Ni_0.25Al₃ alloys. Electrochemical analysis showed that not only did V_0.75Ni_0.25Al₃ outperform VAl₃ but also it was among the best non-noble metal topological HER electrocatalysts currently available.

Synergistic effect of S-bridged Fe-Ni group on hydrogen evolution for pentlandite

Pentlandite is reported to exhibit good catalytic activity in hydrogen evolution reaction (HER). Many studies have paid attention to metal catalysis of pentlandite. However, the nonmetal catalysis is not considered for HER. Here, we unravel one probable catalytic mechanism of pentlandite toward HER using density functional theory. In our study models, (001) and (100) surfaces are created because there are three types of S-bridged M-M groups on them. Our study reveals that (Fe-Ni)-S center has a moderate value of Gibbs free energy while the corresponding value for (Fe-Fe)-S or (Ni-Ni)-S center is largely positive or negative. In (Fe-Ni)-S group, Fe and Ni can regulate the antibonding state of S, and then balance adsorption and desorption of proton. In addition, an intrinsic electronic potential difference exists between Fe and Ni in (Fe-Ni)-S group, which may boost the charge transfer. Particularly, (Fe-Ni)-S groups are perpendicular to the surface, and four of them make up one closed loop in the surface. It is suggested that the behaviors of such configuration composed of reaction centers resemble edge sites along the layers of MoS₂ toward HER. This study provides a deep insight into the synergistic effect of S-bridged Fe-Ni groups and enables the modulation of electrocatalytic reaction of pentlandite toward HER.

Boosting the efficiency and stability of CoMoS4 by N incorporation for electrocatalytic hydrogen evolution

Here, an in situ N incorporation method was developed to boost the efficiency and durability of CoMoS₄ electrocatalyst for hydrogen evolution. Theoretical and experimental results reveal that such modification not only reduces the energy barrier of H* desorption by decreasing the electron densities around active metal sites, but also decreases the leaching rates of the metal ions with enhanced stability.

Distinctive MoS2-MoP nanosheet structures anchored on N-doped porous carbon support as a catalyst to enhance the electrochemical hydrogen production

The fabricated MoS₂-MoP/NC heterojunction electrocatalyst showed a low overpotential, small Tafel slope and excellent stability in alkaline and acidic media.

Hierarchical Fe3 C-Mo2 C-Carbon Hybrid Electrocatalysts Promoted through a Strong Charge-Transfer Effect

Highly efficient, stable, and low-cost catalysts for electrochemical water splitting play a critical role in promoting energy efficiency in the renewable hydrogen power-related industries. In this study, nonprecious metal carbides composed of Fe₃ C and Mo₂ C supported by carbon nanoplates are prepared and utilized as bifunctional electrocatalysts for overall water splitting. Spatially confined annealing of the polydopamine-coated metal precursors affords a structure containing porous cubes isolated by carbon nanoplates encapsulated with Fe₃ C and Mo₂ C nanoparticles. The hybrid electrocatalyst with a hierarchical structure, large surface area, and abundant exposed active sites benefits from efficient mass transport and more importantly the strong charge-transfer effect between the iron and molybdenum moieties. Under strong alkaline conditions, the optimized Fe₃ C-Mo₂ C hybrid (with a Fe/Mo ratio of 1 : 2) requires a low overpotential of 274 and 301 mV for the electrocatalytic oxygen evolution reaction at current densities of 10 and 100 mA cm^-2 , respectively, accompanied with decent hydrogen evolution activity, thereby demonstrating efficient bifunctional electrocatalytic activity towards overall water splitting.

Superconductivity enhancement in phase-engineered molybdenum carbide/disulfide vertical heterostructures

Stacking layers of atomically thin transition-metal carbides and two-dimensional (2D) semiconducting transition-metal dichalcogenides, could lead to nontrivial superconductivity and other unprecedented phenomena yet to be studied. In this work, superconducting α-phase thin molybdenum carbide flakes were first synthesized, and a subsequent sulfurization treatment induced the formation of vertical heterolayer systems consisting of different phases of molybdenum carbide-ranging from α to γ' and γ phases-in conjunction with molybdenum sulfide layers. These transition-metal carbide/disulfide heterostructures exhibited critical superconducting temperatures as high as 6 K, higher than that of the starting single-phased α-Mo₂C (4 K). We analyzed possible interface configurations to explain the observed moiré patterns resulting from the vertical heterostacks. Our density-functional theory (DFT) calculations indicate that epitaxial strain and moiré patterns lead to a higher interfacial density of states, which favors superconductivity. Such engineered heterostructures might allow the coupling of superconductivity to the topologically nontrivial surface states featured by transition-metal carbide phases composing these heterostructures potentially leading to unconventional superconductivity. Moreover, we envisage that our approach could also be generalized to other metal carbide and nitride systems that could exhibit high-temperature superconductivity.

MoSe2-Ni3Se4 Hybrid Nanoelectrocatalysts and Their Enhanced Electrocatalytic Activity for Hydrogen Evolution Reaction

Combining MoSe₂ with other transition metal dichalcogenides to form a hybrid nanostructure is an effective route to enhance the electrocatalytic activities for hydrogen evolution reaction (HER). In this study, MoSe₂-Ni₃Se₄ hybrid nanoelectrocatalysts with a flower-like morphology are synthesized by a seed-induced solution approach. Instead of independently nucleating to form separate nanocrystals, the Ni₃Se₄ component tends to nucleate and grow on the surfaces of ultrathin nanoflakes of MoSe₂ to form a hybrid nanostructure. MoSe₂-Ni₃Se₄ hybrid nanoelectrocatalysts with different Mo:Ni ratios are prepared and their HER catalytic activities are compared. The results show that the HER activities are affected by the Mo:Ni ratios. In comparison with pure MoSe₂, the MoSe₂-Ni₃Se₄ hybrid nanoelectrocatalysts having a Mo:Ni molar ratio of 2:1 exhibit enhanced HER properties with an overpotential of 203 mV at 10 mA/cm² and a Tafel slope of 57 mV per decade. Improved conductivity and increased turnover frequencies (TOFs) are also observed for the MoSe₂-Ni₃Se₄ hybrid samples.

Molecular-scale cage-confinement pyrolysis route to size-controlled molybdenum carbide nanoparticles for electrochemical sensor

Herein, size-controllable molybdenum carbide nanoparticles (Mo₂C NPs) encapsulated by N, P-codoped carbon shells which simultaneously wrapping on the surface of carbon nanotube (Mo₂C@NPC/CNT) is synthesized through a molecular-scale cage-confinement pyrolysis route. Such confinement achieves a good coating and protection of Mo₂C and the effective control over the size of Mo₂C NPs ranging from 2.5 to 10 nm facilitates a rational investigation into their electrochemical sensor behavior at nanometer scales. The optimized structure consisting of Mo₂C nanoparticles with size of ~5 nm showed an outstanding electrochemical response toward dopamine (DA) and acetaminophen (AC) with detection limits (S/N = 3) of 0.008 μM for AC and 0.01 μM for DA.

Sustainable hydrogen production by molybdenum carbide-based efficient photocatalysts: From properties to mechanism

Hydrogen is considered to be a promising energy carrier to solve the issue of energy crisis. Molybdenum carbide (Mo_xC) is the typical material, which has similar properties of Pt and thought to be an attractive alternative to noble metals for H₂ evolution. The study of Mo_xC as alternative catalyst for H₂ production is almost focused on electrocatalytic field, while the application of Mo_xC as a co-catalyst in photocatalytic H₂ evolution has received in-depth research in recent years. Particularly, Mo_xC exhibits significant enhancement in the H₂ production performance of semiconductors under visible light irradiation. However, a review discussing Mo_xC serving as a co-catalysts in the photocatalytic H₂ evolution is still absent. Herein, the recent progress of Mo_xC on photocatalytic H₂ evolution is reviewed. Firstly, the preparation methods including chemical vapor deposition, temperature programming, and organic-inorganic hybridization are detailly summarized. Then, the fundamental structure, electronic properties, and specific conductance of Mo_xC are illustrated to illuminate the advantages of Mo_xC as a co-catalyst for H₂ evolution. Furthermore, the different heterojunctions formed between Mo_xC and other semiconductors for enhancing the photocatalytic performance are emphasized. Finally, perspectives regarding the current challenges and the future research directions on the improvement of catalytic performance of Mo_xC-based photocatalysts are also presented.

Development of core–shell structured Mo2C@BN as novel microwave catalysts for highly effective direct decomposition of H2S into H2 and S at low temperature

Direct decomposition of hydrogen sulfide is an attractive approach for producing CO_x-free H₂ and S from a toxic and abundant waste gas.

Mo2C-embedded biomass-derived honeycomb-like nitrogen-doped carbon nanosheet/graphene aerogel films for highly efficient electrocatalytic hydrogen evolution

Honeycomb-like Mo₂C@nitrogen-doped carbon nanosheet/graphene aerogel films were synthesized successfully by solid-state reaction between (NH₄)₆Mo₇O₂₄ and regenerated chitin/graphene oxide aerogel.

Boron triggers the phase transformation of Mo x C (α-MoC1-x /β-Mo2C) for enhanced hydrogen production

As highly efficient non-precious metal-based catalysts for the hydrogen evolution reaction (HER), molybdenum carbides have attracted much attention over the phase and structure modification for the improvement of HER performances. In this work, a novel strategy is proposed to modulate phases of molybdenum carbides by boron doping, so that the HER performances can be well controlled. After B-doping, the HER activity of the as-prepared B30 catalyst is significantly enhanced with a much smaller Tafel slope of 78 mV dec-1 than that of the blank one (134 mV dec-1), which originates from the increased amount of active sites, enhanced turnover frequency of each active site and reduced electron transfer resistance. Moreover, this work could broaden our view of phase regulation and provide more possible perspectives for the application in other fields.

Co,N-Codoped porous vanadium nitride nanoplates as superior bifunctional electrocatalysts for hydrogen evolution and oxygen reduction reactions

Developing efficient and low-cost bifunctional electrocatalysts as candidates for Pt-based materials to satisfy commercial applications in the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is still very challenging. Herein, we show that Co,N-codoped porous vanadium nitride (VCoN) nanoplates are successfully synthesized via a simple one-step pyrolysis protocol without the use of NH3 gas. We also demonstrate that the crystallization, surface chemical state and porosity of vanadium nitride are well modulated by inventively using Co dopants as structural inducers. The resulting VCoN material exhibits an excellent catalytic activity towards the HER in alkaline media, with an extremely low onset potential of -0.03 V, an overpotential of 179 mV at 10 mA cm-2, and a remarkable durability for over 100 h. Moreover, it shows a superior ORR performance, which compares favorably with commercial 20% Pt/C, exhibiting an onset potential of ∼1.02 V, a half-wave potential of ∼0.91 V and a weak potential shift (-5 mV) after 2000 cycles at 1600 rpm in 0.1 M KOH. Such excellent electrocatalytic performance primarily contributes to the unique structural features of the heteroatom N (pyrrolic and graphitic N) and Co codoping in favor of improving the electrical conductivity and the high porosity contributing to exposing numerous catalytic active sites.

Charge Engineering of Mo2C@Defect-Rich N-Doped Carbon Nanosheets for Efficient Electrocatalytic H2 Evolution

Charge engineering of carbon materials with many defects shows great potential in electrocatalysis, and molybdenum carbide (Mo2C) is one of the noble-metal-free electrocatalysts with the most potential. Herein, we study the Mo2C on pyridinic nitrogen-doped defective carbon sheets (MoNCs) as catalysts for the hydrogen evolution reaction. Theoretical calculations imply that the introduction of Mo2C produces a graphene wave structure, which in some senses behaves like N doping to form localized charges. Being an active electrocatalyst, MoNCs demonstrate a Tafel slope as low as 60.6 mV dec-1 and high durability of up to 10 h in acidic media. Besides charge engineering, plentiful defects and hierarchical morphology also contribute to good performance. This work underlines the importance of charge engineering to boost catalytic performance.

Facile preparation of molybdenum carbide (Mo2C) nanoparticles and its effective utilization in electrochemical sensing of folic acid via imprinting

Herein, we propose a facile chemical reduction method to synthesize the molybdenum carbide (Mo₂C) nanoparticles and its application for the electrochemical detection of folic acid (FA) through imprinting technique. Raman scattering, photoelectron spectroscopy and electron microscopy techniques were employed to study the properties of Mo₂C nanoparticles. FA imprinting was carried out in the presence of pyrrole monomer over Mo₂C modified glassy carbon electrode (GCE). The proposed sensor showed the detection behavior for wide range of FA concentrations from 0.01 μM to 120 μM with an excellent LOD value of 4 nM and good selectivity toward FA as compared to other co-existing species in real samples. The fabricated MIP-Mo₂C/GCE sensors were able to be replicated with ∼1.9% RSD, and their reproduced sensor offered good repeatability (RSD; 1.6%) and stability.

Amorphous phosphorus-doped MoS2 catalyst for efficient hydrogen evolution reaction

Splitting water is an important method for producing clean and sustainable hydrogen to replace finite fossil fuels in future energy systems. MoS₂ is reported as a promising catalyst without noble metallic elements to accelerate the rate of the electrocatalytic hydrogen evolution reaction. However, there is a real need and strong demand for further improvement of the MoS₂-based catalyst. In the present study, a novel amorphous phosphorus-doped MoS₂ nanocomposite (P-MoS₂) is prepared by a facile hydrothermal method. Compared with crystalline molybdenum disulfide, the amorphous P-doped MoS₂ catalyst exhibits much better activity with a smaller Tafel slope of 39 mV dec^-1. Moreover, good stability is also demonstrated over the P-MoS₂ catalyst in acidic electrolyte. This highly active amorphous P-doped MoS₂ catalyst is a promising candidate to facilitate the development of economical hydrogen production systems.

Big to Small: Ultrafine Mo2 C Particles Derived from Giant Polyoxomolybdate Clusters for Hydrogen Evolution Reaction

Due to its electronic structure, similar to platinum, molybdenum carbides (Mo₂ C) hold great promise as a cost-effective catalyst platform. However, the realization of high-performance Mo₂ C catalysts is still limited because controlling their particle size and catalytic activity is challenging with current synthesis methods. Here, the synthesis of ultrafine β-Mo₂ C nanoparticles with narrow size distribution (2.5 ± 0.7 nm) and high mass loading (up to 27.5 wt%) on graphene substrate using a giant Mo-based polyoxomolybdate cluster, Mo₁₃₂ ((NH₄ )₄₂ [Mo₁₃₂ O₃₇₂ (CH₃ COO)₃₀ (H₂ O)₇₂ ]·10CH₃ COONH₄ ·300H₂ O) is demonstrated. Moreover, a nitrogen-containing polymeric binder (polyethyleneimine) is used to create MoN bonds between Mo₂ C nanoparticles and nitrogen-doped graphene layers, which significantly enhance the catalytic activity of Mo₂ C for the hydrogen evolution reaction, as is revealed by X-ray photoelectron spectroscopy and density functional theory calculations. The optimal Mo₂ C catalyst shows a large exchange current density of 1.19 mA cm^-2 , a high turnover frequency of 0.70 s^-1 as well as excellent durability. The demonstrated new strategy opens up the possibility of developing practical platinum substitutes based on Mo₂ C for various catalytic applications.

Graphene oxide supported cobalt phosphide nanorods designed from a molecular complex for efficient hydrogen evolution at low overpotential

The cathodic current density (cd) of GO-Co₂P is 20/100 mA cm⁻² at an overpotential of 80/154 mV. At 100 mA cm⁻² cd, stability is observed for 70 h.

Exploring Burstein–Moss type effects in nickel doped hematite dendrite nanostructures for enhanced photo-electrochemical water splitting

The Burstein–Moss suggests which that the optical band gap of degenerately doped semiconductors increases when all states close to the conduction band get populated is important to obtain different optical properties for the same material.

Structural Design and Electronic Modulation of Transition-Metal-Carbide Electrocatalysts toward Efficient Hydrogen Evolution

As the key of hydrogen economy, electrocatalytic hydrogen evolution reactions (HERs) depend on the availability of cost-efficient electrocatalysts. Over the past years, there is a rapid rise in noble-metal-free electrocatalysts. Among them, transition metal carbides (TMCs) are highlighted due to their structural and electronic merits, e.g., high conductivity, metallic band states, tunable surface/bulk architectures, etc. Herein, representative efforts and progress made on TMCs are comprehensively reviewed, focusing on the noble-metal-like electronic configuration and the relevant structural/electronic modulation. Briefly, specific nanostructures and carbon-based hybrids are introduced to increase active-site abundance and to promote mass transportation, and heteroatom doping and heterointerface engineering are encouraged to optimize the chemical configurations of active sites toward intrinsically boosted HER kinetics. Finally, a perspective on the future development of TMC electrocatalysts is offered. The overall aim is to shed some light on the exploration of emerging materials in energy chemistry.