High Hydrogen Evolution Reaction Activity Research Articles

Phase Engineering and Dispersion Stabilization of Cobalt toward Enhanced Hydrogen Evolution.

Phase engineering is promising to increase the intrinsic activity of the catalyst toward hydrogen evolution reaction (HER). However, the polymorphism interface is unstable due to the presence of metastable phases. Herein, phase engineering and dispersion stabilization are applied simultaneously to boost the HER activity of cobalt without sacrificing the stability. A fast and facile approach (plasma cathodic electro deposition) is developed to prepare cobalt film with a hetero-phase structure. The polymorphs of cobalt are realized through reduced stacking fault energy due to the doping of Mo, and the high temperature treatment resulted from the plasma discharge. Meanwhile, homogeneously dispersed oxide/carbide nanoparticles are produced from the reaction of plasma-induced oxygen/carbon atoms with electro-deposited metal. The existence of rich polymorphism interface and oxide/carbide help to facilitate H2 production by the tuning of electronic structure and the increase of active sites. Furthermore, oxide/carbide dispersoid effectively prevents the phase transition through a pinning effect on the grain boundary. As-prepared Co-hybrid/CoO_MoC exhibits both high HER activity and robust stability (44mV at 10mA cm-2, Tafel slope of 53.2mV dec-1, no degradation after 100 h test). The work reported here provides an alternate approach to the design of advanced HER catalysts for real application.

Hierarchical multiphase heterointerfaces Ni2P–CoP/MoO2 catalyst for efficient and stable hydrogen evolution reaction over the entire pH range

The development of pH-versatile, high-performing, and durable catalysts for hydrogen evolution reaction (HER) is crucial to satisfy the complex environment of water electrolysis industry. Herein, we present the synthesis of a hierarchical multiphase heterointerfaces Ni2P–CoP/MoO2 nanocatalyst with exceptionally high HER activity in the entire pH range through a facile three-step process involved hydrothermal, electrodeposition, and in situ phosphating treatment. Experiments and characterization revealed the strong electronic interactions among the phases of Ni2P, CoP, and MoO2, which endowed the Ni2P–CoP/MoO2 with high hydrogen evolution activity in different pH ranges. Meanwhile, the layered structure of our as-prepared catalyst makes the massive exposure of active sites. As a result, the Ni2P–CoP/MoO2 catalyst shows remarkable performance, requiring mere overpotentials of 33, 41, and 23 mV to drive 10 mA cm−2 in 1 M KOH, 1 M phosphate buffer solution, 0.5 M H2SO4, respectively. Moreover, the catalyst exhibits excellent stability in the chronopotentialmetry test under different pH electrolyte. Impressively, the Ni2P–CoP/MoO2 catalyst coupled with Ni–Fe LDH to form an overall water splitting system only require 1.50 V to drive 10 mA cm−2. Furthermore, this system actuated by wind and solar energy can stably undergo a continuous production of hydrogen and oxygen.

Crystalline Phase Engineering to Modulate the Interfacial Interaction of the Ruthenium/Molybdenum Carbide for Acidic Hydrogen Evolution.

Ruthenium (Ru) is an ideal substitute to commercial Pt/C for the acidic hydrogen evolution reaction (HER), but it still suffers from undesirable activity due to the strong adsorption free energy of H* (ΔGH*). Herein, we propose crystalline phase engineering by loading Ru clusters on precisely prepared cubic and hexagonal molybdenum carbide (α-MoC/β-Mo2C) supports to modulate the interfacial interactions and achieve high HER activity. Advanced spectroscopies demonstrate that Ru on β-Mo2C shows a lower valence state and withdraws more electrons from the support than that of Ru on α-MoC, indicative of a strong interfacial interaction. Density functional theory reveals that the ΔGH* of Ru/β-Mo2C approaches 0 eV, illuminating an enhancement mechanism at the Ru/β-Mo2C interface. The resultant Ru/β-Mo2C exhibits an encouraging performance in a proton exchange membrane water electrolyzer with a low cell voltage (1.58 V@ 1.0 A cm-2) and long stability (500 h@ 1.0 A cm-2).

Electrocatalyst for hydrogen evolution and H2O2 recognition on composite carbon paste electrodes with three new Ag(I) MOFs

Three new Ag(I) metal-organic frameworks (Ag-MOFs) containing bisbenzimidazole-derived ligand, namely, {[Ag2(L)(TP)](H2O)}n (1), {[Ag2(L)(HBTC))(H2O)](CH3CH2OH)(H2O)}n (2) and {[Ag4(L)2(IP)2](CH3CN)3(H2O)16}n (3) (L = bis(1-(pyridin-4-ylmethyl)-benzimidazol-2-yl methyl) ether, TP = Terephthalate, BTC = Benzenetricarboxylate, IP = Isophthalate), have been synthesized by volatilization method and systematic adjustment of solvent and aromatic polyacid co-ligand. Single crystal structural analysis showed that although three Ag-MOFs have a three-dimensional (3D) network backbone structure, their topological structures are different. Electrocatalytic hydrogen evolution reaction (HER) of carbon paste composite electrodes (Ag-MOF-1∼3@CPE) prepared by mixing graphite powder with Ag-MOFs were investigated in 0.5 M H2SO4 electrolyte. The HER measurements show that the overpotential η10293K of Ag-MOF-1∼3@CPE are -634, -533 and -615 mV compared with sCPCE (blank electrode, -966 mV), and the Tafel slope of sCPCE and Ag-MOF-1∼3@CPE were 276, 251, 123 and 220 mV dec−1, respectively. The results prove that Ag-MOF-1∼3@CPE could effectively catalyze and accelerate the HER behavior, with electrocatalytic activity order being Ag-MOF-2@CPE > Ag-MOF-3@CPE > Ag-MOF-1@CPE > sCPE. The highest HER activity of Ag-MOF-2@CPE can be attributed to the fact that Ag-MOF-2 contains coordination water molecule, while the higher activity of Ag-MOF-3@CPE than Ag-MOF-1@CPE is due to steric hindrance. Furthermore, the recognition performance of Ag-MOF-1∼3@CPE for H2O2 was further studied by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6). The three sensors can detect H2O2 in a linear range from 0.5 μM to 4 mM with sensitivities of 103, 34.5 and 138 μA·mM−1·cm−2, and also revealed long-term stability and good selectivity. Our study provides a new approach for designing efficient, non-precious metal electrochemical catalysts.

Atomically precise Pdm(SR)n nanoclusters for efficient hydrogen evolution reaction

Thiolate (SR) protected noble metal nanoclusters have grasped immense attention because of their promising applications in electrocatalysis, electrochemical sensors, photoluminescencse, supercapacitor and energy production. Among the noble metals, numerous reports have highlighted interesting results for Au25(SR)18, Au22(SR)18 and Ag44(SR)30 clusters but Pd and Pt nanoclusters are less addressed. Room temperature ionic liquids (RTIL) show enhanced electrocatalytic activity and stability as a binding matrix as compared to commercial binders like Nafion, Polyvinylidene fluoride (PVDF) and so on. Here, we have synthesised water-soluble thiolate 3-mercaptopropyl sulfonate (MPS) capped Palladium nanoclusters (Pd-MPS NCs). Further, Poly Acrylamide Gel Electrophoresis (PAGE), a separation technique was used to isolate size-dependent NCs and their electrocatalytic activity for the hydrogen evolution reaction (HER) with room temperature ionic liquid as a binding matrix was demonstrated. The electron microscope images of isolated Pd-MPS NCs from these three bands (obtained from PAGE separation) resulted with size ranges of 0.8-1.8 nm, 2-4 nm and 4.2-8 nm respectively. Among the three bands obtained from PAGE gel from the crude Pd NCs, the ultrasmall Pdm(SR)n NCs was isolated from the lower band resulted in high HER activity with less overpotential of 197 mV and a Tafel slope of 125.2 mV dec-1 as compared to Pd-MPS NCs obtained from the other two distinctive bands.

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.

Spin Polarization of 2D Weyl Semimetal Fe2Sn Enabling High Hydrogen Evolution Reaction Activity.

It is well known that magnetic field is one of the effective tools to improve the activity of hydrogen evolution reaction (HER), but considering the inconvenient application of an external magnetic field, it is essential to find a ferromagnetic material with high HER activity itself. Fortunately, recent study has shown that the two-dimmention (2D) Fe2Sn monolayer is a stable ferromagnetic topological Weyl semimetal material with high Tc of 433 K. Here, we report the Fe2Sn monolayer can be used as an alternative HER catalyst compared with expensive platinum (Pt). Our first-principles results show that the Gibbs free energy (ΔGH*) value of the spin polarized Fe2Sn monolayer is -0.06 eV, much better than that without considering spin polarization (-1.23 eV). Moreover, the kinetic analysis demonstrates that the HER occurs on the Fe2Sn monolayer according to the Volmer-Tafel mechanism with low energy barriers. Hence, our findings provide obvious evidence for spin-polarization-improved HER activity, paving a new way to design high-performance HER catalysts.

Co3O4/C derived from ZIF-67 cathode enhances the microbial electrosynthesis of acetate from CO2

Microbial Electrosynthesis (MES) is an electrochemical reduction technology that efficiently converts CO2 into chemicals by electrically driving microbial catalysts. However, the lower mass transfer efficiency of CO2 and hydrogen H2 affected the performance of the MES. In this study, Co3O4/C is derived from the carbonization of ZIF-67 with different temperature (700 °C,800 °C,900 °C), in which some Co ions are exposed and a large number of catalytically active sites are supplied. Among them, the Co3O4/C with 800 °C had the highest hydrogen evolution reaction activity and the lowest internal resistance. The Co3O4/C with 800 °C showed the highest hydrogen production rate of 81.34 × 102 mol day−1, which was 4.4 times higher than that of the bare carbon felt. Furthermore, the Co3O4/C with 800 °C modified cathode was beneficial to the formation of biofilm and improved the enrichment of Acetobacterium and Arcobacter. The highest acetate yield of 0.19 g L−1d−1 was obtained by Co3O4/C with 800 °C, which was 2.1 times higher than that of bare carbon felt, and the corresponding acetate concentration reached 5.61 ± 0.1 g L−1. Co3O4/C derived from ZIF-67 with good H2 production and CO2 adsorption ability is an effective strategy to improve MES cathode.

High hydrogen evolution activities of dual-metal atoms incorporated N-doped graphenes achieved by coordination regulation

Electrolysis of water to produce hydrogen (H) can solve the current energy crisis and environmental problems. However, efficient hydrogen evolution reaction (HER) catalysts are still limited to a few noble metals, thus prohibiting their broad applications. Herein, first-principles calculations were carried out to investigate the theoretical HER performances of a series of N-doped graphenes containing inexpensive single- and dual-metal atoms. Among them, MN4-gra (M = Fe, Co, Ni), homonuclear MMN6-gra, and heteronuclear M1M2N6-gra mostly exhibit low HER activities due to the weak H adsorption, and only CoN4-gra, NiNiN6-gra, and CoNiN6-gra show better ΔG *H values of 0.19, 0.15 and 0.27 eV, respectively. In contrast, low-coordinated MMN5-gra and M1M2N5-gra both have rather high HER activities. In particular, the ΔG *H values of FeNiN5-gra and CoNiN5-gra are as low as -0.04 and -0.06 eV, respectively, very close to the ideal 0 eV. Detailed analyses reveal that such high activity mainly stems from the reduced metal coordination and the synergistic effect between the two metals, which greatly enhance the adsorption ability of the active center. More interestingly, the strong H adsorption of MMN5-gra /M1M2N5-gra could enable them to further adsorb a second H atom and generate a stable HMH intermediate to yield the final product H2. Under this novel mechanism, the two-step |ΔG *H| values of FeNiN5-gra and CoNiN5-gra are all no more than 0.10 eV. Our work not only discloses the important effect of coordination regulation and site synergy on enhancing the catalytic activity but also finds a new HER path on the metal-embedded N-doped graphenes.

ZnO monolayer-supported single atom catalysts for efficient electrocatalytic hydrogen evolution reaction.

Hydrogen is identified as one of the most promising sustainable and clean energy sources. The development of a hydrogen evolution reaction (HER) catalyst with high activity is essential to meet future needs. Considering the novel advantages of two-dimensional materials and the high catalytic activity of atomic transition metals, in this study, using density functional theory calculations, the HER on a single transition metal (10 different TM atoms) adsorbed and doped ZnO monolayer (ZnO-m) has been investigated. The Volmer-Tafel reaction mechanisms and strain engineering of the three best HER catalysts are also discussed. The results show that Pt@ZnO-m, Co-doped ZnO-m and Ir-doped ZnO-m with high stability all have a smaller absolute H adsorption free energy than Pt, and the optimal value of Pt@ZnO-m is -0.017 eV. The calculation of the reaction energy barriers shows that the Volmer-Tafel step is favorable. Co@ZnO-m and Ir@ZnO-m have high HER activity, the widest pH range, and acid-alkali resistance. Pt@ZnO-m and Co-doped ZnO-m maintain excellent HER performances in the strain range of -4% to 4%.

An in situ phase transformation induced mesoporous heterointerface for the alkaline hydrogen evolution reaction.

The phase structure of a catalyst plays a crucial role in determining the catalytic activity. In this study, a facile phosphorization process is employed to achieve the in situ phase transformation from single-phase Co3O4 to CoO/CoP hybrid phases. Characterization techniques, including XRD, BET, SEM, and TEM, confirm the retention of the mesoporous nature during the phase transformation, forming porous CoO/CoP heterointerfaces. Strong charge transfer is observed across the CoO/CoP heterointerface, indicating a robust interaction between the hybrid phases. The CoO/CoP hybrid exhibits significantly enhanced catalytic activity for the alkaline hydrogen evolution reaction (HER) compared to pristine Co3O4. Density Functional Theory (DFT) calculations reveal that the elimination of the band gap in the spin-down band of Co in CoO/CoP contributes to the observed high HER activity. The findings highlight the potential of CoO/CoP hybrids as efficient catalysts for HER, and contribute to the advancement of catalyst design for sustainable energy applications.

Structure transformation induced bi-component Co–Mo/A-Co(OH)2 as highly efficient hydrogen evolution catalyst in alkaline media

Elucidating the inherent origins of the sluggish hydrogen evolution reaction (HER) kinetics in alkaline media and developing high-performance electrocatalysts are fundamental for the advances of conventional alkaline water electrolyzers and emerging anion exchange membrane (AEM) electrolyzers. Here we present a facile electrochemical modification strategy for the synthesis of bi-component Co–Mo(18%)/A-Co(OH)2 catalyst toward efficient HER catalysis in alkaline media. Porous Co–Mo alloys with adjustable Mo/Co atomic ratio are first prepared by H2-assisted cathodic electrodeposition. By virtue of the appropriate electronic structure and hydrogen binding energy, Co–Mo(18%) is the most HER active among the alloys and is further activated by a constant-current electrochemical modification process. Physical characterizations reveal the formation of amorphous Co(OH)2 nanoparticles on the surface. Electrokinetic analysis combined with theoretical calculations reveal that the in-situ formed Co(OH)2 can efficiently promote the water dissociation, resulting in accelerated Volmer-step kinetics. As a result, the Co–Mo(18%)/A-Co(OH)2 simultaneously achieves the optimization of the two factors dominating alkaline HER activity, i.e., water dissociation and hydrogen adsorption/desorption via the bifunctional synergy of the bi-components. The high HER activity (η10 of 47 ​mV at 10 ​mA ​cm−2) of Co–Mo(18%)/A-Co(OH)2 is close to benchmark Pt/C catalyst and comparable or superior to the most active non-noble metal catalysts.

Insights into the hydrogen evolution reaction in vanadium redox flow batteries: A synchrotron radiation based X-ray imaging study

The parasitic hydrogen evolution reaction (HER) in the negative half-cell of vanadium redox flow batteries (VRFBs) causes severe efficiency losses. Thus, a deeper understanding of this process and the accompanying bubble formation is crucial. This benchmarking study locally analyzes the bubble distribution in thick, porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms. Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs. The study systematically varies the electrode potential and material, concluding that more negative electrode potentials of −200 mV vs. reversible hydrogen electrode (RHE) and lower cause more substantial bubble formation, resulting in bubble fractions of around 15%–20% in carbon felt electrodes. Contrarily, the bubble fractions stay only around 2% in an electrode combining carbon felt and carbon paper. The detected areas with high HER activity, such as the border subregion with more than 30% bubble fraction in carbon felt electrodes, the cutting edges, and preferential spots in the electrode bulk, are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses. The described combination of electrochemical measurements, local X-ray micro-tomography, AI-based segmentation, and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes, providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.

Rh-WO3 Electrocatalyst for Hydrogen Evolution Reaction in the Alkaline Seawater Electrolyte

One potential strategy to develop hydrogen evolution electrocatalysts for producing sustainable hydrogen in water electrolysis is creating electrocatalysts with low-cost, high activity, and high stability. Herein, we show that low-loading metal-based tungsten oxide (WO3) can be used as electrocatalysts for the hydrogen evolution reaction (HER) in acid, alkaline, and alkaline seawater electrolytes. Among prepared electrocatalysts, rhodium (Rh)-WO3 exhibits a high HER activity with the values of overpotential of 48, 116, and 98 mV to obtain a current density of 10 mA.cm-2 in acid, alkaline, and alkaline seawater electrolytes, respectively. In addition, the Rh-WO3 electrocatalyst shows high stability during the HER operation for over 60,000s. Besides, the application of Rh-WO3 electrocatalyst as cathode and commercial ruthenium oxide (RuO2) as an anode for overall water splitting show excellent efficiency with only a potential of 1.45 V to a current density of 10 mA.cm-2 in the alkaline-seawater electrolyte. The Rh-WO3//RuO2 cell also exhibits high stability for over 40,000s. The results provide evidence that Rh-WO3 can be a promising HER catalyst for sustainable hydrogen production via alkaline-seawater electrolysis application, as show in Figure 1. Figure 1

The Influence of Doping in the Electrocatalytic Properties of NiFe2O4-Derived Nitrides

Transition metal nitrides (TMNs) have been widely studied in the last years due to their extraordinary properties such as high electrical conductivity and versatile physical and chemical properties. They can be easily synthesize from metal oxide precursors and, in addition, they display electrocatalytic activities similar to Pt and other conventional noble metal electrocatalysts.1 Among them, several Ni-, Co- and Fe-based nitrides have been studied as electrocatalysts for the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).2–4 The combination of these metals in different proportions (stoichiometric and non-stoichiometric) can give place to a wide range of electrocatalysts with better electrochemical performance than the single metal nitrides. Apart from them, 2nd and 3rd row TMNs like Mo- and W-based nitrides can display high HER activity, surpassing those 1st row TMNs above-mentioned, therefore doping 1st row TMNs with Mo or W, even in very small amounts, can increase significantly the electrocatalytic performance of these materials.5 In this work, NiFe2O4-derived nitrides and their Mo- and W-doped versions were synthesized via the resorcinol-formaldehyde sol-gel polymerization method, followed by nitridation in ammonia atmosphere. The influence of doping for the HER, ORR and OER reactions in alkaline electrolyte has been studied. As observed, W-doping results in improved ORR and OER activities. Characterization techniques, such as XRD, TEM and XPS, are being performed in the initial and used catalysts, observing a structural change from the initial oxide (NiFe2O4) to the final nitride (NiFe2N), including the doped versions, which can help to understand their electrocatalytic properties.

Operando construction of nickel-modifiedamorphous 2D CaTiO3 nanosheets for enhanced photocatalytic hydrogen production

We report the successful preparation of an amorphous nickel-modified 2D CaTiO3 photocatalyst via a methanol co-precipitation method. The Ni was operando constructed into the CaTiO3 surface, leading to improved separation of photoinduced charge carriers and enhanced photocatalytic hydrogen evolution reaction (HER) under solar light irradiation. The optimized photocatalyst yields a high HER activity of 1.7 mmol/g/h in the presence of glycerol as a hole scavenger. Our findings suggest that the amorphous form of the catalyst and the loading of Ni contribute to the improved photocatalytic activity. Our results demonstrate for the first time that amorphous 2D CaTiO3 with operando-constructed nickel can produce sacrificial hydrogen, highlighting the potential of amorphous materials for sustainable energy conversion applications.

Electronic structure optimizing of Ru nanoclusters via Co single atom and N, S co-doped reduced graphene oxide for accelerating water electrolysis

The development of efficient and stable electrocatalysts for hydrogen evolution reaction (HER) is impending for the advancement of water-splitting. In this study, we developed a novel electrocatalyst consisting of highly dispersed Ru nanoclusters ameliorated by cobalt single atoms and N, S co-doped reduced graphene oxide (CoSARuNC@NSG). Benefitted from the optimized electronic structure of the Ru nanoclusters induced by the adjacent single atomic Co and N, S co-doped RGO support, the electrocatalyst exhibits exceptional HER performance with overpotentials of 15 mV and 74 mV for achieving a current density of 10 mA cm−2 in alkaline and acidic water. The catalyst outperforms most noble metal-based HER electrocatalysts. Furthermore, the electrolyzer assembled with CoSARuNC@NSG and RuO2 demonstrated an overall voltage of 1.56 V at 10 mA cm−2 and an excellent operational stability for over 25 h with almost no attenuation. Theoretical calculations also deduce its high HER activity demonstrated by the smaller reaction energy barrier due to the optimized electronic structure of Ru nanoclusters. This strategy involving the regulation of metal nanoparticles activity through flexible single atom and GO support could provide valuable insights into the design of high-performance and low-cost HER catalysts.

Effect of electron transfer of 2D Ti3C2Tx@MOF heterostructure on hydrogen evolution reaction activity

Metal-organic framework (MOF) layers were grown in situ from 2D transition metal carbides (MXenes, Ti3C2Tx) at room temperature to obtain the two-dimensional (2D) Ti3C2Tx@MOF heterostructures with a tightly connected interface. This interface provided more titanium atoms in the low-valence state in comparison to the original Ti3C2Tx, thus facilitating more electron transfer from Ti3C2Tx to MOF-(Fe/Co) nanosheets. The charge density difference and density functional theory results disclosed that Ti3C2Tx could modulate the electronic density around the active sites and lower ΔGH* energy barrier of 2D MOF-(Fe/Co) nanosheets towards the improved hydrogen evolution reaction (HER) activity. The obtained 2D Ti3C2Tx@MOF heterostructures exhibited a much higher HER activity in 1 M KOH electrolyte (with the overpotential of 104 mV at 10 mA/cm2 and Tafel slope of 79 mV/dec) than those of 2D Ti3C2Tx@MOF-TH, 2D MOF nanosheets, and Ti3C2Tx nanosheets. This research provides a basis for developing superior 2D MOFs, which can enhance HER properties through efficient electronic transport at the heterojunction interface.

Surface/Interface Engineering of Hierarchical MoO2/MoNi4@Ru/RuO2 Heterogeneous Nanosheet Arrays for Alkaline Water Electrolysis with Fast Kinetics

Comprehensive SummaryRealizing the hydrogen economy by water electrolysis is an attractive approach for hydrogen production, while the efficient and stable bifunctional catalysts under high current densities are the bottleneck that limits the half‐cell reactions of water splitting. Here, we propose an approach of hydrothermal and thermal annealing methods for robust MoO2/MoNi4@Ru/RuO2 heterogeneous cuboid array electrocatalyst with multiplying surface‐active sites by depositing a monolayer amount of Ru. Benefiting from abundant MoO2/MoNi4@Ru/RuO2 heterointerfaces, MoO2/MoNi4@Ru/RuO2 heterogeneous cuboid array electrocatalysts effectively drive the alkaline water splitting with superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances. The synthesized MoO2/MoNi4@Ru/RuO2 has high HER activity, which realizes the working overpotentials of 48 mV at 50 mA·cm–2, further achieving overpotentials of 230 mV for industry‐level 1000 mA·cm–2 in alkaline water electrolysis. Moreover, it also showed an enhanced OER activity than commercial RuO2 with a small overpotential of 280 mV at 200 mA·cm–2 in alkaline media. When building an electrolyzer with electrodes of (–)MoO2/MoNi4@Ru/RuO2IIMoO2/ MoNi4@Ru/RuO2 (+), a cell voltage of 1.63 V and 1.75 V is just required to support the current density of 200 mA·cm–2 and 500 mA·cm–2 in alkaline water electrolysis, much lower than that of the electrolyzer of (–)Pt/CIIRuO2(+). This work demonstrates that MoO2/MoNi4@Ru/RuO2 heterogeneous nanosheet arrays are promising candidates for industrial water electrolysis applications, providing a possibility for the exploration of water electrolysis with a large current density.