Sites For Hydrogen Evolution Reaction Research Articles

Oxidation of Ni(H2O)6@MoO3 to Ni2O3/MoO3 Composites by Aerial Annealing: Electrocatalytic Hydrogen Evolution.

Molybdenum trioxide (α-MoO3) is a promising and inexpensive alternative to platinum group metals (PGMs), for electrocatalytic hydrogen evolution reaction (HER). However, to make it a viable candidate for electrocatalytic systems, we must address the hurdles associated with its inferior electrical conductivity and lack of active sites. Unlike Mo-based compounds such as MoS2 and MoSe2, which possess catalytically active edges, α-MoO3 lacks inherent active sites for HER. Previous studies have employed various strategies to activate MoO3 for HER, yet its activation in near-neutral conditions remain largely unexplored. In this study, a previously known α-MoO3 intercalating {Ni(H2O)6}2+, [MoVI2O6(CH3COO){NiII(H2O)6}0.5]·H2O (Ni(H2O)6@MoO3) is prepared via a simple and scalable room-temperature aqueous synthesis. In the subsequent aerial thermal annealing process at 300, 400 and 500 °C, Ni(H2O)6@MoO3 acts as a self-sacrificial template, yielding mixed metal oxide composites of nickel and molybdenum (named as MoO3-300, MoO3-400 and MoO3-500). The HR-TEM and XPS analyses confirm the formation of the Ni2O3 phase alongside the orthorhombic α-MoO3. The annealing temperature plays a key role in the crystallinity, phase, morphology, and electrocatalytic performance of the resulting composites. The composite formed at 400 °C (MoO3-400) shows the best electrocatalytic performance among them.

Understanding Pt Active Sites on Nitrogen-Doped Carbon Nanocages for Industrial Hydrogen Evolution with Ultralow Pt Usage.

Engineering microstructures of Pt and understanding the related catalytic mechanism are critical to optimizing the performance for hydrogen evolution reaction (HER). Herein, Pt dispersion and coordination are precisely regulated on hierarchical nitrogen-doped carbon nanocages (hNCNCs) by a thermal-driven Pt migration, from edge-hosted Pt-N2Cl2 single sites in the initial Pt1/hNCNC-70 °C catalyst to Pt clusters/nanoparticles and back to in-plane Pt-NxC4-x single sites. Thereinto, Pt-N2Cl2 presents the optimal HER activity (6 mV@10 mA cm-2) while Pt-NxC4-x shows poor HER activity (321 mV@10 mA cm-2) due to their different Pt coordination. Operando characterizations demonstrate that the low-coordinated Pt-N2 intermediates derived from Pt-N2Cl2 under the working condition are the real active sites for HER, which enable the multi-H adsorption mechanism with an ideal H* adsorption energy of nearly 0 eV, thereby the high activity, as revealed by theoretical calculations. In contrast, the high-coordinated Pt-NxC4-x sites only allow the single-H adsorption with a positive adsorption energy and thereby the low HER activity. Accordingly, with an ultralow Pt loading of only 25 μgPt cm-2, the proton exchange membrane water electrolyzer assembled using Pt1/hNCNC-70 °C as the cathodic catalyst achieves an industrial-level current density of 1.0 A cm-2 at a low cell voltage of 1.66 V and high durability, showing great potential applications.

Unveiling active sites in FeOOH nanorods@NiOOH nanosheets heterojunction for superior OER and HER electrocatalysis in water splitting

The development of cost-effective, highly active, and stable electrocatalysts for water splitting to produce green hydrogen is crucial for advancing clean and sustainable energy technologies. Herein, we present an innovative in-situ synthesis of FeOOH nanorods@NiOOH nanosheets on nickel foam (FeOOH@NiOOH/NF) at an unprecedentedly low temperature, resulting in a highly efficient electrocatalyst for overall water splitting. The optimized FeOOH@NiOOH/NF sample, evaluated through time-dependent studies, exhibits exceptional oxygen evolution reaction (OER) performance with a low overpotential of 261 mV at a current density of 20 mA cm−2, alongside outstanding hydrogen evolution reaction (HER) activity with an overpotential of 150 mV at a current density of 10 mA cm−2, demonstrating excellent stability in alkaline solution. The water-splitting device featuring FeOOH@NiOOH/NF-2 electrodes achieves a voltage of 1.59 V at a current density of 10 mA cm−2, rivalling the state-of-the-art RuO2/NF||PtC/NF electrode system. Density functional theory (DFT) calculations unveil the efficient functionality of the Fe sites within the FeOOH@NiOOH heterojunction as the active OER catalyst, while the Ni centres are identified as the active HER sites. The enhanced performance of OER and HER is attributed to the tailored electronic structure at the heterojunction, modified magnetic moments of active sites, and increased electron density in the dx2-y2 orbital of Fe. This work provides critical insights into the rational design of advanced electrocatalysts for efficient water splitting.

Few-shot learning for screening 2D Ga2CoS4−x supported single-atom catalysts for hydrogen production

Hydrogen generation and related energy applications heavily rely on the hydrogen evolution reaction (HER), which faces challenges of slow kinetics and high overpotential. Efficient electrocatalysts, particularly single-atom catalysts (SACs) on two-dimensional (2D) materials, are essential. This study presents a few-shot machine learning (ML) assisted high-throughput screening of 2D septuple-atomic-layer Ga2CoS4−x supported SACs to predict HER catalytic activity. Initially, density functional theory (DFT) calculations showed that 2D Ga2CoS4 is inactive for HER. However, defective Ga2CoS4−x (x = 0–0.25) monolayers exhibit excellent HER activity due to surface sulfur vacancies (SVs), with predicted overpotentials (0–60 mV) comparable to or lower than commercial Pt/C, which typically exhibits an overpotential of around 50 mV in the acidic electrolyte, when the concentration of surface SV is lower than 8.3%. SVs generate spin-polarized states near the Fermi level, making them effective HER sites. We demonstrate ML-accelerated HER overpotential predictions for all transition metal SACs on 2D Ga2CoS4−x. Using DFT data from 18 SACs, an ML model with high prediction accuracy and reduced computation time was developed. An intrinsic descriptor linking SAC atomic properties to HER overpotential was identified. This study thus provides a framework for screening SACs on 2D materials, enhancing catalyst design.

Constructing of n‐Type Semiconductor Heterostructures for Efficient Hydrazine‐Assisted Hydrogen Production

AbstractHydrazine‐assisted water electrolysis presents a promising approach toward energy‐efficient hydrogen production. However, the progress of this technology is hindered by the limited availability of affordable, efficient, and durable catalysts. In this study, a feasible strategy is proposed for interface modulation that enables efficient hydrogen evolution and hydrazine oxidation through the construction of n‐type semiconductor heterostructures. The metal–semiconductor contacts are rationally designed using ruthenium nanoclusters and a range of metal oxide (M–O) semiconductor heterostructures, including p‐type semiconductor substrates (NiO, Co3O4, NiCo2O4, CuCo2O4, ZnCo2O4) and n‐type semiconductor substrate (Fe2O3). Intriguingly, Ru nanoclusters supported on p‐type M–O substrates induce a transition from p‐type M–O to n‐type M‐O/Ru. The design of n‐type semiconductor heterostructures can significantly reduce space‐charge regions and increase charge carrier concentration, thereby improving the electrical conductivity of electrocatalysts. Moreover, Ru atoms can serve as highly efficient active sites for hydrogen evolution reaction and hydrazine oxidation reaction. The NiO/Ru heterostructure can drive current densities of 10 and 100 mA cm−2 with only 0.021 and 0.22 V cell voltages for hydrazine‐assisted water electrolysis. This work provides new insights for the development of highly efficient semiconductor catalysts, enabling energy‐saving hydrogen production.

Constructing novel Sn-Mo bimetallic sulfide heterostructures for enhanced catalytic performance towards the hydrogen evolution reaction

Understanding the design principles of efficient electrocatalysts using the structure–activity relationship is crucial for the advancement of energy-related applications, and specifically the hydrogen evolution reaction (HER). Non-precious electrocatalysts with low overpotentials are essential for driving the HER and achieving high energy efficiency. In this study, we synthesized and thoroughly investigated various heterostructures combining Mo and Sn sulfides, ranging from complete phase-separated hybrids to homogeneous mixtures: SnS@MoS2 core–shell structures, SnS/MoS2 with edge-rich Mo and (SnxMo1-x)S with uniformly distributed Sn-Mo. Our findings reveal that the SnS@MoS2 structure exhibited relatively high intrinsic activity characterized by a high electrochemical active surface area and rapid charge transfer kinetics, thereby enhancing the HER catalytic performance. The presence of fluffy MoS2 layers provided an abundance of optimized sites for HER, potentially due to strain and defects such as S vacancies, known as active catalytic sites. The optimal structure facilitated efficient charge transfer from the core to the shell, improving conductivity and catalytic activity. Our research highlights the advantages of a core–shell hybrid structure, offering guiding principles for the development of an optimal SnS@MoS2 catalyst.

Black Titanium Oxide/Activated TaS2 Flakes Photoelectrode for Plasmon Assisted Hydrogen Evolution at Neutral pH at High Current Density.

A heterojunction photo-electrode(s) consisting of porous black titanium oxide (bTiO2) and electrochemically self-activated TaS2 flakes is proposed and utilized for hydrogen evolution reaction (HER). The self-activated TaS2 flakes provide abundant catalytic sites for HER and the porous bTiO2, prepared by electrochemical anodization and subsequent reduction serves as an efficient light absorber, providing electrons for HER. Additionally, Au nanostructures are introduced between bTiO2 and TaS2 to facilitate the charge transfer and plasmon-triggering ability of the structure created. After structure optimization, high HER catalytic activity at acidic pH and excellent HER activity at neutral pH are achieved at high current densities. In particular, with the utilization of bTiO2@TaS2 photoelectrode (neutral electrolyte, sunlight illumination) current densities of 250 and 500mA cm-2 are achieved at overpotentials of 433, and 689mV, respectively, both exceeding the "benchmark" Pt. The addition of gold nanostructures further reduces the overpotential to 360 and 543mV at 250 and 500mA cm-2, respectively. The stability of the prepared electrodes is investigated and found to be satisfying within 24 h of performance at high current densities. The proposed system offers an excellent potential alternative to Pt for the development of green hydrogen production on an industrial scale.

Phosphorus Defect Mediated Electron Redistribution to Boost Anion Exchange Membrane‐Based Alkaline Seawater Electrolysis

AbstractIt is of essential importance to design bifunctional electrocatalysts with excellent performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater splitting. Herein, an approach for manipulating electron redistribution in NiCoP treated by P defect (Pv) engineering (NiCoPv@NF) is presented, exhibiting excellent catalytic activities and stability toward HER/OER in alkaline seawater solution. The Pv reduces the surface electrooxidation reconfiguration energy barrier, making it easier to drive the local conversion of crystals to active oxy(hydroxide) in OER. In addition, the Ni site of NiCoPv and the Co site of NiCoOOH are the active sites for HER and OER processes, respectively. In situ generated PO43− adsorbed on the catalyst surface causes spatial repulsion, preventing Cl− corrosion in seawater electrolysis. The seawater AEM electrolyzer using NiCoPv@NF couple achieves excellent performance of high activity (2.43 V at 500 mA cm−2) and long‐term durability (500 mA cm−2 over 110 h). The working efficiency of AEM in 1.0 M KOH is as high as 77.0% at 100 mA cm−2 with the price of per GGE H2 as low as $ 0.87.

MoS2-CuCo2S4 nanosheets with a honeycomb structure formed on Ni foam: An efficient electrocatalyst for hydrogen evolution reaction

The physical, chemical, and electrocatalytic properties of conventional single-component electrocatalysts developed for the hydrogen evolution reaction (HER) no longer match the needs of many commercial applications. This necessitates for the creation of more sophisticated and effective electrocatalysts for the HER. In this study, MoS2-CuCo2S4 was loaded onto NF using a simple two-step hydrothermal method. In the resultant NF/MoS2-CuCo2S4 material, CuCo2S4 offers a lot of active sites to support vertically arranged MoS2 nanosheets, thereby decreasing their agglomeration. Moreover, the heterogeneous structure formed between CuCo2S4 and MoS2 facilitates charge transfer and exposes the active sites for HER, further improving the electrochemical hydrogen evolution performance of the heterostructured electrocatalyst. In a 1.0 M KOH solution, the synthesized NF/MoS2-CuCo2S4 nanosheet catalyst has outstanding electrocatalytic efficacy, with an overpotential as low as 67 mV at a current density of 10 mA·cm−2.

In Situ Reconstruction to Surface Sulfide Adsorbed Metal Scaffold for Enhanced Electrocatalytic Hydrogen Evolution Activity

AbstractTransition‐metal‐based compounds have been intensively explored as efficient electrocatalysts for hydrogen evolution reaction (HER). Feasible reconstruction to the real active sites, which is yet to be identified, endows the promotion of HER activity. Here, it is reported that the incoming S coordinates and anion vacancies prompt the structural reconstruction of S‐doped Co3O4 on carbon cloth (S‐Co3O4/CC) during HER. A list of in situ studies reveals that the real active sites for HER are the “metallic surface‐adparticles” system embracing metallic Co scaffold and the dilute coverage of S coordinated Coδ+. Reaction mechanism exploration illustrates that interfacial perimeters between the coverage of Co3S4 moieties and metallic Co considerably facilitate the adsorption of H*, improve the kinetics of water dissociation, and consequently promote HER activity. The exemplified sulfide‐mediated topotactic transformation strategy is extended to the preparation of S, Fe codoped Ni(OH)2 (S‐NiFe/CC) as a bifunctional electrocatalyst. The assembled anion exchange membrane water electrolyzer achieves a current density of 1.0 A cm−2 at 1.72 V, showing excellent capability in catalyzing overall water splitting at ampere level. This study, showing a feasible strategy that enables the facile reconstruction to identify active sites, would inspire the development of efficient electrocatalysts for HER and other electrochemical hydrogenation reaction.

Boosting Efficient Alkaline Hydrogen Evolution Reaction of CoFe-Layered Double Hydroxides Nanosheets via Co-Coordination Mechanism of W-Doping and Oxygen Defect Engineering.

While surface defects and heteroatom doping exhibit promising potential in augmenting the electrocatalytic hydrogen evolution reaction (HER), their performance remains unable to rival that of the costly Pt-based catalysts. Yet, the concurrent modification of catalysts by integrating both approaches stands as a promising strategy to effectively address the aforementioned limitation. In this work, tungsten dopants are introduced into self-supported CoFe-layered double hydroxides (LDH) on nickel foam using a hydrothermal method, and oxygen vacancies (Ov) are further introduced through calcination. The analysis results demonstrated that tungsten doping reduces the Ov formation energy of CoFeW-LDH. The Ov acted as oxophilic sites, facilitating water adsorption and dissociation, and reducing the barrier for cleaving HO─H bonds from 0.64 to 0.14eV. Additionally, Ov regulated the electronic structure of CoFeW-LDH to endow optimized hydrogen binding ability on tungsten atoms, thereby accelerating alkaline Volmer and Heyrovsky reaction kinetics. Specifically, the abundance of Ov induced a transition of tungsten from a six-coordinated to highly active four-coordinated structure, which becomes the active site for HER. Consequently, an ultra-low overpotential of 41mV at 10 mAcm-2, and a low Tafel slope of 35mVdec-1 are achieved. These findings offer crucial insights for the design of efficient HER electrocatalysts.

Doping induced mixed polytypic interfaces of MoS2 for superior electrocatalytic hydrogen evolution

Metallic 1Tphase of MoS2 is desirable for accelerating electrochemical hydrogen generation from water due to its excellent electrical conductivity. However, it is challenging to synthesize stable 1T-MoS2 on a large scale using conventional chemical or physical routes. Here in, we report highly durable Mn-doping assisted in-plane 1T/2H mixed phases of MoS2 synthesized by a simple one-step hydrothermal method. The Mn-doping not only results in a favourable electronic modification in the host lattice but also in a structural evolution from 2H (trigonal prismatic) to 1T (octahedral) phase through sulfur-plane gliding with additional defects. The 1T/2H interfaces exhibit more active sites for hydrogen evolution reaction (HER) than its bulk 2H-counterpart. The developed electrode shows relatively low overpotential of 95 mV at a current density of 10 mA/cm2 and a low Tafel slope of 72 mV/dec in 0.5 M H2SO4. In addition, Density Functional Theory based calculations also support that Mn-doping in pristine 2H-MoS2 encourages a structural phase separation. Locally hybridized d-orbitals of Mn induce the formation of 2H/1T interfaces. It results in the delocalization of electrons, and thus facilitates the hydrogen adsorption and desorption process, better than the 2H phase.

High-Throughput Designed and Laser-Etched NiFeCrVTi High-Entropy Alloys with High Catalytic Activities and Corrosion Resistance for Hydrogen Evolution in Seawater.

Electrocatalytic hydrogen evolution from seawater through wind or solar energy is a cost-effective way to produce green hydrogen fuel. However, the lack of highly active and anti-corrosive electrocatalysts in seawater severely hinders the industrial application. Herein, a novel Ni1.1FeCr0.4V0.3Ti0.3 high-entropy alloy (HEA) is designed through high throughput computing and prepared via powder metallurgy with the surface treated by laser etching under different laser power. The laser-etched NiFeCrVTi high-entropy alloys exhibit a unique periodically ordered structure with multiple active centers and high porosity. The Ni-HEA-30 displays remarkable hydrogen evolution reaction (HER) performance with an overpotential of 55.9mV and a Tafel slope of 47.3mV dec-1 in seawater. Density functional theory (DFT) calculations are applied to identify the real active sites for HER on the HEA surface as the key factor for both proton and intermediate transformation, which also reveals that the Cr atom promotes the adsorption energy of water molecules, and the modulation of the electronic structure plays a crucial role in optimizing the hydrogen binding capabilities of the Ni atoms within the alloy. Additionally, the electrocatalyst displays high corrosion resistance in seawater, contributing to the good durability for hydrogen production. This work uncovers a new paradigm to develop novel electrocatalysts with superior reaction activity in seawater.

Tailoring the morphology of Mo2S3/MoP2 composite thin films via aerosol assisted chemical vapor deposition for enhanced hydrogen evolution reaction performance

In this study, we report on the fabrication of Mo2S3/MoP2 composite thin films using a single-step aerosol assisted chemical vapor deposition method from a single-source precursor solution of [(ƞ5-Cp)Mo(CO)2(S2P(SC6H4Me)2)] (1). Deposition times of 20, 30, and 40 min were used to obtain thin films with different morphologies. Our investigation found that the 30-minute thin film, which had a widely distributed grainy morphology, exhibited the highest electrocatalytic performance for hydrogen evolution reaction (HER) as determined by linear sweep voltammetry studies. This film required the lowest applied potential of 250 mV to generate a current density of 10 mAcm−2 with a low charge transport resistance of 715 Ω, despite having the lowest charge donor density of 5.52 × 1019 cm−3. We found that the unique morphology of this thin film enhanced electron mobility, resulting in superior HER performance with a Tafel slope of ∼123 mVdec−1 and a higher current charge density of 0.408 mAcm−2 due to increased active sites for HER. The Mo2S3/MoP2 heterostructure exhibited favourable band gaps of ∼2.2 and ∼2.7 eV, respectively, resulting in a synergistic effect that allowed for effective electron transfer. Our study concludes that different deposition durations produced composite thin films with altered morphologies that exhibit dissimilar electrochemical kinetics in HER.

Self‐integration exactly constructing oxygen‐modified MoNi alloys for efficient hydrogen evolution

AbstractIntroducing oxygen atoms into nickel‐based alloys is an effective strategy for constructing water dissociation sites for hydrogen evolution reaction (HER). However, controlling oxygen content to realize the best match of water dissociation and hydrogen adsorption is challenging. Herein, we exploit the self‐integration process of MoNi alloy in molten salts to introduce oxygen atoms, which ultimately leads to the localized generation of robust NiOxHy around the MoNi alloys. Interestingly, Mo is further doped into NiOxHy (Mo‐NiOxHy) to construct an effective active center for water dissociation due to the high mobility in ionic solutions. Owing to the covering and space confinement of molten salt, MoNi alloy is exactly decorated with Mo‐NiOxHy nanosheets. Both physical characterization and density functional theory calculation prove that the electron transport, water dissociation capability, and hydrogen adsorption of MoNi are finely tuned and benefited from the O and Mo doping, thus greatly expediting HER kinetics. Mo‐NiOxHy exhibits a much lower overpotential of 33 mV at 10 mV cm−2 in alkaline electrolyte, even superior to the Pt/C benchmark. Moreover, the final Mo‐NiOxHy requires a low overpotential of 57 mV at 10 mV cm−2 in acidic media. This enhancement is ascribed to the successful assembly of MoNi foam elicited by molten salt.

Constructing a Functionalized Electrocatalyst of a Transition Metal Chalcogenide on Accordion-Like MXene to Boost the Hydrogen Evolution Reaction.

MXenes exhibit unique layered structures and excellent electrical conductivity, and their multiple surface termination groups are favorable for hosting impressive performance for electrochemical reactions. Therefore, a two-dimensional (2D) layered MXene-based catalyst may become a novel high-efficiency electrocatalyst to replace traditional noble metal electrocatalysts. In this work, a transition metal chalcogenide (MoS2/CuS) and MXene are combined to prepare a 2D electrocatalyst (MoS2/CuS/MXene) for the hydrogen evolution reaction (HER). MXene exhibited a large specific surface area in the shape of an accordion, which was very beneficial for the growth of nanomaterials. CuS/MXene promoted electron transfer and improved the exposed active site for HER. The exposed MoS2 edges exhibited a high chemical adsorption capacity, which is conducive to HER. Electrochemical tests reveal that the MoS2/CuS/MXene electrocatalyst can reduce the charge transfer resistance toward the HER and increase active sites for HER, leading to enhancing the catalytic performance. The MoS2/CuS/MXene electrocatalyst affords an efficient HER with a low overpotential (115 mV@10 mA cm-2). This work offers a new idea to create layered transition metal chalcogenide- and MXene-based electrocatalysts for HER.

Phosphidation treatment of surfactant-tuned iron polyphthalocyanine grown in situ on nickel foam: An efficient bifunctional catalyst for overall water splitting

Developing robust electrocatalysts for overall water splitting is vital for industrial hydrogen production on a large scale. Herein, we obtain a bifunctional electrocatalyst NF@FePPc-s/p (where s represents surfactant and p stands for the phosphidation treatment) by phosphorization of surfactant (F127)-tuned iron polyphthalocyanine (FePPc) grown in situ on the nickel foam (NF) substrate. The as-obtained NF@FePPc-s/p exhibits the golden needle mushroom-like morphology, which is conducive to fully exposing the active sites and boosting the electron-transfer kinetics at the reaction interface. The physicochemical characterization and electrochemical measurements demonstrate that the active Fe2P and Ni2P phases formed during the phosphidation treatment are intrinsically active catalytic sites for hydrogen evolution reaction (HER), and the FeOOH formed from phase transformation of Fe2P during the oxygen evolution reaction (OER) process contributes a lot to enhancement of the OER activity. Furthermore, the electronic interaction between Fe and Ni further improves the electrocatalytic performances for both reactions. The optimized NF@FePPc-s/p catalyst exhibits remarkable OER (293 mV@100 mA cm−2) and HER (190 mV@100 mA cm−2) activities in 1.0 M KOH electrolyte. The water electrolyzer assembled with the NF@FePPc-s/p as the cathode and anode electrodes, respectively, only requires a low cell voltage of 1.743 V to obtain the current density of 100 mA cm−2 for overall water splitting, outperforming the precious NF@RuO2–Pt/C based electrolyzer (1.852 V).

Heterogeneous Cu incorporated into Ni6Fe2-LDH/rGO induces spin exchange interaction to enhance alkaline hydrogen evolution

The efficiency of hydrogen evolution reaction (HER) takes an important influence on electrochemical water electrolysis, yet it still delivers sluggish kinetics mainly due to the high kinetic energy barriers. Herein, Cu1Ni5Fe2-Layered double hydroxides/reduced graphene oxide (denoted as Cu1Ni5Fe2-LDHs/rGO) with heterogeneous Cu atoms incorporated into Ni6Fe2-LDHs/rGO is constructed through a hydrothermal method and doping strategy in this works, wherein the subtle lattice distortion is availably regulated and optimized by Cu2+ Jahn-Teller effect, offering more active sites for HER. As benefits of the subtle lattice distortion and the spin exchange interaction, Cu1Ni5Fe2-LDHs/rGO displays ferromagnetism at room temperature and shows superior alkaline HER properties with a relatively low overpotentials of 50 mV at 10 mA cm−2 in 1.0 M KOH. The low Tafel slope of 38 mV dec−1 implies Cu1Ni5Fe2-LDHs/rGO owns an ultra-fast HER kinetic. This study can offer a new strategy to construct high efficient HER catalysts based on transition metal NiFe-LDHs.

Analyzing electrocatalytically accessible sites for hydrogen evolution reaction in rGO doped copper cobalt sulphide

An important, yet difficult problem is the rational design and controlled production of an electrocatalyst for hydrogen evolution reaction (HER) using graphene-based bimetallic sulphide. Here, a novel electrocatalyst for HER was designed and created using a spherical-shaped structure grown on a graphene sheet with a conductive Cu-CoS2 support (rGO@CuCoS2). It takes advantage of the synergistic effect between the copper and cobalt sulphide phases, the naturally low resistance of the bimetal substrate, and the uniform spherical structure. With overpotentials of 84 mV at a current density of 10 mA cm−2 in alkaline electrolytes, the self-supported rGO@CuCoS2 composite catalyst demonstrates outstanding electrocatalytic activity for HER in an alkaline pH range, respectively. The created rGO@CuCoS2 catalyst impressively exhibits steady electrocatalytic activity and high durability in HER processes. The electrocatalytically accessible sites were also discovered to be 15.02 x 1017 sites at a 5 mV s−1 scan rate. This novel mix of methods is intended to offer a workable plan for the advancement of human energy and is promising much beyond the realm of water electrolysis.

Modulation of active site environment in an embedded CuOx@TiO2 photocatalyst for enhanced hydrogen evolution and CO2 reduction

Cocatalyst act as the active site usually plays an important role in both photocatalytic hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2RR). As the size, distribution, location, contact behavior with semiconductor etc. show significant effects for the activity. In this work, the active site environment (aggregation state of the active site of the cocatalyst) was modulated by locating the different amounts of CuOx nanoparticles (NPs) into the porous TiO2 (CuOx@TiO2), which was achieved by calcination of Cu@MIL-125 as the precursor. The composition, morphology, and chemical state of the catalyst were analyzed by a series of characterization methods. The results showed that the embedded CuOx NPs exhibited obviously better dispersion than the externally supported ones, especially at the high loading amount. Cu NPs totally transformed to CuO at the lower loading amount, while it transformed to CuOx with partial Cu (I) species existence at the higher loading amount. Photocatalytic reactions showed that the activity of CuOx@TiO2 was ∼ twice that of the traditional outside loading catalyst CuOx/TiO2 in both HER and CO2RR. The high HER activity was obtained at relatively lower loading capacity (0.200 wt%∼0.500 wt%), while CO2RR was the advantageous reaction at higher loading capacity (5.000∼15.000 wt%). Apparently, CuOx@TiO2 offered a quite different active site environment for the two type of reactions. The embedded structure can provide highly dispersed single active sites for HER at lower loading capacity, while it facilitates the formation of multi-electron environment under irradiation for CO2RR at higher loading capacity. The construction of an appropriate active center environment determines the occurrence of high-efficiency photocatalytic reactions.