Electrocatalyst For Efficient Water Splitting Research Articles

Spectroscopic Investigations of Complex Electronic Interactions by Elemental Doping and Material Compositing of Cobalt Oxide for Enhanced Oxygen Evolution Reaction Activity

AbstractDoping and compositing are two universal design strategies used to engineer the electronic state of a material and mitigate its disadvantages. These two strategies are extensively applied to design efficient electrocatalysts for water splitting. Using cobalt oxide (CoO) as a model catalyst, it is proven that the oxygen evolution reaction (OER) performance can be progressively improved, first by Fe‐doping to form Fe‐CoO solid solution, and further by the addition of CeO2 to produce a Fe‐CoO/CeO2 composite. X‐ray absorption spectroscopy (XAS) reveals that distinct electronic interactions are induced by the processes of doping and compositing. Fe‐doping of CoO can break down the structural symmetry, changing the electronic structure of both Co and O species at the surface and decreasing the flat‐band potential (Vfb). In comparison, subsequent compositing of Fe‐CoO with CeO2 induces negligible electronic changes in the Fe‐CoO (as seen in ex situ characterizations), but significantly modifies the oxidative transformations of both Co and Fe under OER conditions. The spectroscopic investigations reveal that Fe‐doping and CeO2 compositing play different roles in modifying the electronic properties of CoO in its pristine state and during OER catalysis, in return, providing useful guidance for the design of more efficient electrocatalysts using these two strategies.

Facet‐Junction Induced Strong Metal Support Interaction for Enhanced Alkaline Hydrogen Evolution Reaction

AbstractStrong metal‐support interaction (SMSI) plays a critical role in enhancing the catalytic performance of electrocatalysts. Currently, effective approaches to enhance the SMSI effect in supported electrocatalysts still need to be developed, and a comprehensive atomic‐level understanding of the underlying reaction mechanisms remains unclear. In this study, a novel facet‐junction strategy is proposed to enhance the SMSI between the loaded Ru atoms and the Co3O4 support. By modulating the ratio of exposed facet for (111)/(100) crystal plane in Co3O4, the hydrogen evolution reaction (HER) performance can be dramatically enhanced by 560% and can achieve a Pt‐like HER activity with the overpotential of 45 mV. Detailed analysis with atomic‐resolution integrated differential phase contrast (iDPC)‐scanning transmission electron microscopy (STEM), atomic‐resolution high angle annular dark field (HADDF)‐STEM, and electron energy loss spectroscopy (EELS) further proved that with proper (111)/(100) crystal plane ratio, the intensified charge distribution near the facet‐junction region would modify the electronic structure around the active sites. This work provides new insights to enhance the SMSI and will contribute to the rational design of highly efficient electrocatalysts for water splitting.

α-Mn2O3 porous fibers synthesized by air-heated solution blow spinning (A-HSBS) technique: electrochemical assessment for oxygen evolution reaction in alkaline medium

In this work, we report a novel synthesis route of α-Mn2O3 porous fibers obtained by air-heated solution blow spinning (A-HSBS) and their application as an electrocatalyst for the oxygen evolution reaction (OER). Our α-Mn2O3 porous fibers present superior OER performance to other electrocatalysts reported in the literature, and this is due to a fibrous morphology and multiple Mn oxidate state, which lead to a small overpotential of 378 mV @ 10 mA cm-2. Furthermore, the fibrous α-Mn2O3 electrode exhibits long-term electrochemical stability confirmed by chronopotentiometry testing for 18 h at a current density of 10 mA cm-2 and showing retention/preservation of microstructural properties. Our results underscore the potential of the A-HSBS for producing electrodes with a fiber-like morphology, based on transition metals. The proposed synthesis route can provide economical, durable, and efficient electrocatalysts for water splitting, which can be applied in several applications, such as electrocatalysts, biosensors, among others.

Cobalt-molybdenum bimetallic phosphide grown in situ on nickel foam as a bifunctional electrocatalyst for efficient water splitting

Cobalt-molybdenum bimetallic phosphide grown in situ on nickel foam as a bifunctional electrocatalyst for efficient water splitting

Construction and optimization of multi-interface nanotube structured phosphorus-doped bimetallic oxide arrays as efficient electrocatalysts for water splitting

The multi-interface nanotube structured phosphorus-doped bimetallic oxide P-CoMoO4/CF-1 exhibits remarkable water splitting catalytic activity. The nanotube structure decorated with MOFs arrays with unique surfaces provides abundant active sites.

Recent advances in the role of MXene based hybrid architectures as electrocatalysts for water splitting.

The development of non-noble metal based and cost-effective electrocatalysts for water splitting has attracted significant attention due to their potential in production of clean and green hydrogen fuel. Discovered in 2011, a family of two-dimensional transition metal carbides, nitrides, and carbonitrides, have demonstrated promising performance as electro catalysts in the water splitting process due to their high electrical conductivity, very large surface area and abundant catalytic active sites. However, their-long term stability and recyclability are limited due to restacking and agglomeration of MXene flakes. This problem can be solved by combining MXene with other materials to create their hybrid architectures which have demonstrated higher electrocatalytic performance than pristine MXenes. Electrolysis of water encompasses two half-cell reactions, hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode. Firstly, this concise review explains the mechanism of water splitting. Then it provides an overview of the recent advances about applications of MXenes and their hybrid architectures as HER, OER and bifunctional electrocatalysts for overall water splitting. Finally, the recent challenges and potential outlook in the field have been presented. This concise review may provide further understanding about the role of MXene-based hybrid architectures to develop efficient electrocatalysts for water splitting.

High-Entropy Alloy Nanocages with Highly Ordered {100} Facets and Ultrathin Feature for Water Splitting in Acidic Medium

High-entropy alloy (HEA) nanoparticles have been recognized as one kind of efficient electro-catalyst for water splitting. However, their higher catalytic activity is restrained by the difficulty in precisely shaping the...

Bimetallic Ni2−xCoxP carbon nanofibers network: Solid-Solution-Alloy nano-architecture as efficient electrocatalysts for water splitting

The design of efficient and cost-effective electrocatalysts with the capability of steady work has attracted massive attention in the field of water splitting in recent years. In this paper, the...

Prominent development of Ni-based oxygen-evolving electrocatalysts for water splitting

Achieving a future sustainable carbon-neutral society requires efficient systems for water splitting to produce H2 as alternatives to fossil fuel. Prominent development of Ni-based oxygen-evolving electrocatalysts for efficient water splitting are reviewed.

Electronic synergy between CoP/NiCoP heterostructure and Co, Ni single atoms for efficient hydrogen evolution and overall water splitting

Transition metal phosphides (TMPs) are considered as potential electrocatalysts for hydrogen evolution (HER) and overall water splitting (OWS), but their excessively strong adsorption property toward H* limits the reaction kinetics. Herein, we design a bifunctional electrocatalyst (CoP/NiCoP/Co–Ni–N–C) supported by CoP/NiCoP heterostructure and Co, Ni single atoms, which was prepared via facile one-pot pyrolysis process. The interfacial electronic synergy between the high-electropositive Co–N–C, Ni–N–C and the electron-rich CoP/NiCoP heterostructure balanced the hydrogen binding strength, resulting in fast kinetics and high intrinsic activity. Besides, the g-C3N4 was applied as a self-sacrificial template to construct the N doped hierarchical porous carbon carrier, which provided abundant mass transfer pathways and enhanced the charge transfer efficiency. Additionally, the fluid catalytic cracking (FCC) slurry was intelligently applied as extra carbon source, which not only limited the size of CoP/NiCoP nanoparticles, but also increased the loading of Co and Ni single atoms. Benefit from those advantages, the optimized CoP/NiCoP/Co–Ni–N–C exhibited low overpotentials of 40 mV at 10 mA cm−2 toward HER in 1 M KOH. Meanwhile, the two-electrode system only need 1.54 V to achieve the current density of 10 mA cm−2. This work provided a kind of potential electrocatalyst for efficient water splitting and a method for low-cost catalyst design.

In-situ construction defect-rich CuNiCoS4 /1T-MoS2 heterostructures as superior electrocatalysts for water splitting

Rational design and construction of bifunctional heterostructure electrocatalysts with high-conductivity and more active sites is imperative for water splitting. Herein, based on the tunable property of layered double hydroxide laminates cations, topological transformation technology and template confine method, a series of high-performance bifunctional catalysts composed of transition metal doping NiCo2S4 (MNiCoS4, M = Cu, Fe, Zn, Mn) and 1T-MoS2 were in-situ fabricated on nickel foam. In particular, CuNiCoS4/1T-MoS2 exhibits an ultralow overpotential of 163 mV at 50 mA cm−2 for oxygen evolution reaction (OER) and favorable hydrogen evolution reaction activity. The two-electrode system requires only 1.52 V to attain a current density of 10 mA cm−2. To the best of our knowledge, its OER electrocatalytic activity far exceed state-of-art catalysts reported. The outstanding performance of this series of catalysts can be attributed to two aspects. First, the highly conductive 1T-MoS2 can facilitate electron transfer, and second, the defect-rich heterostructure can effectively regulate the electronic structure of the active metal and expose abundant active sites. This work provides a valuable strategy for developing high activity electrocatalysts for efficient water splitting.

RuO2/CeO2 heterostructure anchored on carbon spheres as a bifunctional electrocatalyst for efficient water splitting in acidic media

The use of proton exchange membrane (PEM) hydrolysis technology holds promise for eco-friendly hydrogen production using renewable energy sources. However, developing efficient, cost-effective, and durable bifunctional electrocatalysts for the acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains challenging. Here, we synthesized RuO2/CeO2 heterojunction loaded on carbon spheres (RuO2/CeO2@C) via hydrothermal and annealing techniques to address this issue. Our experiments demonstrate exceptional catalytic activity of RuO2/CeO2@C for both OER and HER, with overpotentials of 170 and 120 mV, respectively, at 10 mA/cm2 in 0.5 M H2SO4. Moreover, the electrocatalyst enables overall water splitting at 1.54 V and maintains stability for over 100 h at 10 mA/cm2. Density functional theory (DFT) calculations suggest that RuO2/CeO2 heterojunction modifies d-band center of Ru, balances H adsorption/desorption behavior, accelerates reaction kinetics, and lowers the energy barrier, thereby enhancing electrocatalytic activity. These findings provide valuable insights for future efficient bifunctional water splitting electrocatalyst design.

Bimetallic and phosphorus-decorated cobalt molybdate nanosheets as highly active bifunctional electrocatalysts for enhanced overall water splitting

It is very vital to exploit efficient electrocatalysts for water splitting. Herein, we design and fabricate one kind of bimetallic and phosphorus-doped CoMoO4 (P–CoMoO4) nanosheet product with coarse surface and porous structure. The P–CoMoO4 nanosheets possess rectangular architecture with the length and width of ∼2 μm and 500 nm. It is worth noting that the synthetic P–CoMoO4 catalyst displays bifunctional activity for overall water splitting in alkaline electrolyte. The overpotentials are merely 300 and 70.2 mV for OER and HER at 10 mA cm−2, respectively. The water splitting voltage of P–CoMoO4 couple is 1.48 V at 10 mA cm−2, and this couple presents reliably long-term stability for 24 h. This research indicates the important significance of bimetallic and phosphorus-decorated oxides in water electrolysis field.

Iron and vanadium co-doped Ni3S2 flower like nanosheets as an efficient electrocatalysts for water splitting

For the production of sustainable hydrogen energy from water electrolysis, it is now essential to create an efficient bifunctional electrocatalysts for OER and HER (oxygen and hydrogen evolution reaction). We have synthesized a bi-metallic heterogeneous electrocatalyst of iron and vanadium codoped nickel sulphide (FeV-Ni3S2) flower like nanosheets self-supported on conductive nickel foam (NF) substrate by a typical hydrothermal method. Herein, our investigation is focused on achieving an efficient electrocatalytic performance and long-term stability (> 48 h) in an alkaline environment (1 M KOH). The results of FeV-Ni3S2/NF exhibits an outstanding electrochemical performance with lower overpotentials of 149 mV for HER and 183 mV for OER at 10 mA cm−2, and a lower cell voltage of 1.56 V, respectively. The lattice distortion in Ni3S2 caused by FeV-doping, and the enrichment of sulphur active edge sites contributes to the improved electrochemical performance of FeV-Ni3S2/NF. Moreover, the interconnected flower like nanosheets increasese the conductivity, density of active sites and electrochemical surface area to facilitate the mass transport of reactants, benefiting stable water electrolysis for efficient hydrogen production. This work will provide novel insights into the design of bi-metal-doped materials for energy conversion and storage applications.

Nickel-cobalt phosphide nanowires as precatalysts for surface reconstruction to prepare durable and efficient OER catalysts

The investigation of transition metal phosphides (TMPs) as efficient electrocatalysts for water splitting has garnered significant attention in academic research. Nevertheless, limited research has been conducted on the alteration of the structural and morphological properties of TMPs resulting from the unavoidable surface reconstruction during the oxygen evolution reaction (OER). This study introduces a newly developed catalyst, namely nickel–cobalt phosphide nanowires (NiCoP), which facilitates the in-situ growth of nickel–cobalt oxide (NiCo2O4) through surface reconstruction during anodic potential cycling in alkaline electrolytes. The catalyst's extensive modification can be observed through ex-situ characterization techniques. The catalyst undergoes a significant transformation that ultimately yields a phosphide scaffold, leading to the formation of a spinel oxide surface. This transformation enhances the catalytic environment for the OER, making it highly efficient and potent. The transformed catalyst demonstrates comparable catalytic performance to the precious RuO2 catalyst across various current densities. Importantly, it exhibits remarkable long-term stability, as demonstrated by its ability to sustain continuous operation for 72 h at a current density of 50 mA while maintaining stable catalytic performance.

Ambient plasma treated iron-doped flower-shaped molybdenum disulfide for efficient electrocatalyst

Developing a nonprecious, bifunctional, and efficient electrocatalyst for water splitting is crucial for future renewable fuel systems, yet it remains a significant challenge. In this study, we tackle the challenge by activating molybdenum disulfide (MoS2) through iron doping and ambient plasma treatment. We synthesize 1 T phases flower-shaped plasma treated iron-doped MoS2 (P-Fe-MoS2), since 1 T-MoS2 has higher electrocatalytic activity and larger electrical conductivity, compared to 2H-MoS2. P-Fe-MoS2 shows 79 % of 1 T phase, resulting in enhanced catalytic performance, such as low overpotential of −122 mV with Tafel slope of 47 mV/dec at −10 mA/cm2 for hydrogen evolution reaction and low overpotential of 206 mV with Tafel slope of 69 mV/dec at the current density of + 10 mA/cm2 for oxygen evolution reaction. This study shows the development of 1 T phase on the synthesized Fe doped 2H-MoS2 by the ambient plasma method, which could be used widely for modifications of other energy materials.

Bifunctional carbon quantum dot-embedded metal-organic framework nanohybrid as a highly efficient electrocatalyst for water splitting and CO2 reduction

Bifunctional carbon quantum dot (CQD)-embedded metal-organic framework (MOF) (CQD@MOF) nanohybrid as an energy-efficient electrocatalyst is fabricated for electrochemical water splitting and CO2 reduction through a simple and environmentally friendly method using natural resources. Key parameters, such as synthesis temperature, deposition temperature and time, pH and type of electrolyte, and scan rate, are optimized to fabricate binder-free CQD@MOF/nickel foam (NF) electrodes. Excellent hydrogen and oxygen evolution reactions occur with a current density of 50 mA/cm2 at lower overpotentials of 48.00 and 135 mV in a 1 M potassium hydroxide (KOH) electrolyte at a scan rate of 5 mV/s, respectively. In a two-electrode system, the CQD@MOF/NF electrode exhibits a low overpotential of 1.36 V to achieve 10 mA/cm2, confirming the practical feasibility of overall water splitting. Furthermore, the electrode exhibits high chemical stability and robustness even after 4000 cycles and more than 17 h. These results are attributed to the effective combination of substantial adsorption sites and the improved conductivity of the MOF induced by the electron-accepting characteristics of the CQDs with high charge transfer rates during water splitting. Finally, electrochemical CO2 reduction of the CQD@MOF/NF electrode is demonstrated by continuously maintaining a specific current density for 12 h, which can extend the technological potential of carbon nanohybrid as an electrocatalyst for green energy applications.

2D ZIF-67 derived V-doped CoP/NC nanosheets as efficient electrocatalysts for water splitting

The water splitting reaction to produce hydrogen is one of the most promising and cleanest ways to resolve the energy crisis. However, the preparation of efficient and stable electrocatalysts with low-cost remains challenging. In this work, the noble-metal free N-doped carbon (NC) incorporated V-doped cobalt phosphide (CoP) nanosheets on nickel foam (NF) (denoted as V-CoP-NC/NF) are prepared by using two-dimension zeolitic imidazolate framework (ZIF-67) as precursor followed by NaVO3 etching/doping and phosphorization. The V doping is found to be essential to enhance the electrochemical performance of CoP for water splitting. In particular, V5-CoP-NC/NF (V5 represents the concentration of NaVO3 for etching/doping is 5 mM) exhibits the highest hydrogen evolution performance in alkaline electrolyte, to achieve a current density of 10 mA cm−2, an overpotential of 119 mV (vs reversible hydrogen electrode) is required. X-ray photoelectron spectroscopy results show that the V doping significantly altered the binding energies of Co 2p, P 2p and N 1 s in V5-CoP-NC/NF, which is believed to facilitate the adsorption and dissociation of intermediates and accelerate interfacial charge transfer during hydrogen evolution reaction process. This work provides a simple route to prepare heteroatom doped CoP self-standing electrocatalysts for water splitting.

P-doped Co3S4/NiS2 heterostructures embedded in N-doped carbon nanoboxes: Synergistical electronic structure regulation for overall water splitting

Water splitting using transition metal sulfides as electrocatalysts has gained considerable attention in the field of renewable energy. However, their electrocatalytic activity is often hindered by unfavorable free energies of adsorbed hydrogen and oxygen-containing intermediates. Herein, phosphorus (P)-doped Co3S4/NiS2 heterostructures embedded in N-doped carbon nanoboxes were rationally synthesized via a pyrolysis-sulfidation-phosphorization strategy. The hollow structure of the carbon matrix and the nanoparticles contained within it not only result in a high specific surface area, but also protects them from corrosion and acts as a conductive pathway for efficient electron transfer. Density functional theory (DFT) calculations indicate that the introduction of P dopants improves the conductivity of NiS2 and Co3S4, promotes the charge transfer process, and creates new electrocatalytic sites. Additionally, the NiS2-Co3S4 heterojunctions can enhance the adsorption efficiency of hydrogen intermediates (H*) and lower the energy barrier of water splitting via a synergistic effect with P-doping. These characteristics collectively enable the titled catalyst to exhibit excellent electrocatalytic activity for water splitting in alkaline medium, requiring only small overpotentials of 150 and 257 mV to achieve a current density of 10 mA cm−2 for hydrogen and oxygen evolution reactions, respectively. This work sheds light on the design and optimization of efficient electrocatalysts for water splitting, with potential implications for renewable energy production.

The role of manganese-based catalyst in electrocatalytic water splitting: Recent research and progress

Electrocatalytic water splitting is an effective way to produce hydrogen, which is considered as a promising strategy to solve energy crisis and promote energy conversion. But there is still a lack of stable and efficient catalyst. Transition metal (such as Mn, Fe, Co, and Ni) compounds are considered as potential catalyst materials for electrocatalytic water splitting. Among them, manganese-based compounds have the characteristics of low price and abundant reserves. And manganese-based catalysts have attracted extensive attention of researcher due to their diversity of polyvalence and structure as well as morphology. It reviewed that the classification summary and modification method of manganese-based catalysts on the aspect of performance improvement of electrocatalytic water splitting. The classification and summary of manganese-based catalysts from the aspects of single atom and alloy, compound as well as compound composites are summarized in detail, and the current methods and strategies for improving catalytic performance are prominently introduced, emphasizing the regulation and optimization of the catalytic reaction by manganese-based compounds. Finally, in the last part of the review, the further experimental design strategies, the importance of advanced characterization methods and the future development direction of manganese-based catalysts are emphasized. Further understanding of the mechanism by which manganese-based catalysts improve performance will point the way for the design of highly efficient electrocatalysts for water splitting and other possible applications.