Catalysts For Overall Water Splitting Research Articles

Co-doped NixPy loading on Co3O4 embedded in Ni foam as a hierarchically porous self-supported electrode for overall water splitting

It had remained a challenge to rationally design a highly efficient bifunctional catalyst for overall water splitting using non-precious metals. Herein, a simple method was presented to synthesize a self-supported catalyst using nickel foam (NF) filled with nanoscale Co3O4 (Co3O4/NF) as a hierarchical porous support. A NiCoP alloy was deposited on the Co3O4/NF in the form of profiling growth by electroless plating ([email protected]3O4/NF). And then, the [email protected]3O4/NF electrodes were phosphorylated. The profile-grown NiCoP alloy transformed into a two-dimensional (2D) flake-like Co-doped NixPy, forming a self-supported electrocatalyst (Co-NixPy@Co3O4/NF). The Co-NixPy@Co3O4/NF electrode exhibited a large surface area, excellent conductivity, and synergy between metal atoms. This electrode also possessed low overpotentials of 72 and 120 mV to drive the hydrogen and oxygen evolution reactions at 10 mA cm−2. For overall water splitting, the self-supported Co-NixPy@Co3O4/NF electrode only required a low voltage of 1.47 V to reach the current densities of 20 mA cm−2 in 1 M KOH with long-term stability for 36 h. This work represented an achievement the exploration of a new bifunctional of transition metal phosphides with high performances in water splitting.

One-Pot Synthesis of B/P-Codoped Co-Mo Dual-Nanowafer Electrocatalysts for Overall Water Splitting.

Exploring electrocatalysts with satisfactory activity and durability has remained a long-lasting target for electrolyzing water, which is particularly significant for sustainable hydrogen fuel production. Here, we report a quaternary B/P-codoped transition metal Co-Mo hybrid as an efficient alternative catalyst for overall water splitting. The Co-Mo-B-P/CF dual nanowafers were deposited on a copper foam by double-pulse electrodeposition, which is favorable for achieving a nanocrystalline structure. The Co-Mo-B-P/CF catalyst shows a high catalytic activity along with good long-term stability in 1.0 M KOH solutions for both the hydrogen and oxygen evolution reactions, requiring 48 and 275 mV to reach 10 mA cm-2, respectively. The synergetic effect between Co-Mo and doped B and P elements is mainly attributed to the excellent bifunctional catalysis performance, while the dual-nanowafer structure endows Co-Mo-B-P with numerous catalytical active sites enhancing the utilization efficiency of atoms. Moreover, the catalytic capability of Co-Mo-B-P/CF as a bifunctional electrocatalyst for the overall water splitting is proved, with the current density of 10 mA cm-2 accomplished at 1.59 V. After the stability test for overall water splitting at 1.59 V for 24 h, the activity almost remains unchanged. The features of excellent electrocatalytic activity, simple preparation, and inexpensive raw materials for Co-Mo-B-P/CF as a bifunctional catalyst hold great potentials for overall water splitting.

Heteroatoms Adjusting Amorphous FeMn-Based Nanosheets via a Facile Electrodeposition Method for Full Water Splitting

There still exists a resplendent prospect of developing a robust and stable non-noble metal catalyst for overall water splitting. Herein, we designed highly efficient amorphous FeMn-based electroca...

Cu2Se nanowires shelled with NiFe layered double hydroxide nanosheets for overall water-splitting

It is imperative but challenging to develop non-noble metal-based bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Our work reports a core–shell nanostructure that is constructed by the electrodeposition of ultrathin NiFe-LDH nanosheets (NiFe-LDHNS) on Cu2Se nanowires, which are obtained by selenizing Cu(OH)2 nanowires in situ grown on Cu foam. The obtained Cu2Se@NiFe-LDHNS electrocatalyst provides more exposed edges and catalytic active sites, thus exhibiting excellent OER and HER electrocatalytic performance in alkaline electrolytes. This catalyst needs only an overpotential of 197 mV for OER at 50 mA cm−2 and 195 mV for HER at 10 mA cm−2. Besides, when employed as a bifunctional catalyst for overall water-splitting, it requires a cell voltage of 1.67 V to reach 10 mA cm−2 in alkaline media. Furthermore, the corresponding water electrolyzer demonstrates robust durability for at least 40 h. The excellent performance of Cu2Se@NiFe-LDHNS might be ascribed to the synergistic effect from the ultrathin NiFe-LDHNS, the Cu2Se nanowires anchored on the Cu foam, and the formed core–shell nanostructure, which offers large surface area, ample active sites, and sufficient channels for gas and electrolyte diffusion. This work provides an efficient strategy for the fabrication of self-supported electrocatalysts for efficient overall water-splitting.

Facile fabrication of flower-like CuS/MnCO3 microspheres clusters on nickel foam as an efficient bifunctional catalyst for overall water splitting

Utilizing the abundant elements on earth to product inexpensive, high-active and stable catalysts for water splitting is very significant but still remains serious challenge to produce hydrogen. Herein, heterostructures of CuS/MnCO3 on nickel foam substrate are firstly successfully synthesized via a facile one-step hydrothermal strategy. The as-prepared electrocatalyst displays an enhanced oxygen evolution reaction (OER) performance in alkaline conditions with a minimum overpotential of 70 mV and a small Tafel slope of 42.5 mV/dec to achieve 10 mA cm−2. The catalyst also exhibits an excellent HER activity with a low overpotential of 143 mV and the Tafel slope of 51.4 mV/dec to acquire 10 mA cm−2 in 1.0 M KOH. Moreover, when the CuS/MnCO3//CuS/MnCO3 electrode is applied for the overall water splitting, the electrolyzer cell device affords 10 mA cm−2 at a relative low voltage of 1.43 V, which is one of the best catalysts ever reported. In stability test, its activity first decreases and then remains stable in 1 M KOH solution for about 10 h, indicating that the electrode has good electrochemical stability. Density functional theory calculations (DFT) show that MnCO3 has a stronger adsorption energy for water than CuS does, indicating that MnCO3 is a real active center and CuS plays a certain synergistic effect. This work not only provides a low-cost and efficient bifunctional catalyst for water splitting technology, but also extends the application of bifunctional catalyst based on transition metal sulfide and carbonate compound.

Carbon Cloth Supported Nitrogen Doped Porous Carbon Wrapped Co Nanoparticles for Effective Overall Water Splitting

AbstractThe key to the practical application of overall water splitting is to develop high‐efficient non‐noble metal electrocatalysts. Herein, carbon cloth supported N‐doped porous carbon wrapped Co nanoparticles (CC@Co‐NPC) are constructed with high bifunctional catalytic activity toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline medium. Benefiting from the exposure of abundant Co active sites, and the synergistic effect between Co particles and N‐doped carbon species, the CC@Co‐NPC delivers small overpotentials of 286 and 340 mV at 100 mA cm−2 with Tafel values of 59 and 97 mV dec−1 towards OER and HER, respectively. Remarkably, when coupled as CC@Co‐NPC||CC@Co‐NPC cell, only a small voltage of 1.49 V is required to achieve 10 mA cm−2, making CC@Co‐NPC a potential bifunctional catalyst for overall water splitting.

Rh@C8N8 monolayer as a promising single-atom-catalyst for overall water splitting

Development of efficient single-atom-catalysts (SACs) is a promising strategy for electrochemical water splitting. High over-potential and poor stability of catalysts remain to be challenges for overall water splitting. In this work, through the first-principles calculations, we screen a novel series of TM@C8N8 monolayers, constructed by embedding transition metal atoms in our proposed C8N8 monolayer based on poly(pyrazine-2,3-diamine) units using the kinetic stability and the projected density of states. Their catalytic performance of intrinsic TM-N4 moiety is investigated for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) using the Gibbs free energy change (ΔG) of each elementary step. Especially, Rh@C8N8 exhibits superior catalytic activity toward HER and OER with hydrogen adsorption free energy (ΔGH*)/over-potential (η) of 0.08 eV/0.49 V at pH = 7. In addition, it is unbroken at high temperatures (1000 K) using the first-principle molecular dynamics simulation. Therefore, Rh@C8N8 monolayer can perform as an efficient bifunctional catalyst for overall water splitting. It is also expected that our results can serve as the theoretical basis to open the door for future experimental research on novel CN layered-materials containing TM-N4 moiety.

Defect-Rich FeN0.023/Mo2C Heterostructure as a Highly Efficient Bifunctional Catalyst for Overall Water-Splitting

The innovation in highly efficient, stable, and economical bifunctional overall water-splitting electrocatalysts is critical in developing sustainable energy, but it remains challenging. In this research, we have developed an unsophisticated method to synthesize hybrid nanoparticles (FeN0.023/Mo2C/C) uniformly dispersed in nitrogen-doped carbon nanosheets. The two active components FeN0.023 and Mo2C are coupled to form an FeN0.023/Mo2C/C heterostructure being a highly efficient electrocatalyst, which gives low overpotentials of 227/76 mV for OER/HER at 10 mA cm-2 current density. The alkaline-electrolyzer with FeN0.023/Mo2C/C as the anode-cathode catalyst needs merely 1.55 V to reach 10 mA cm-2 and can maintain a stable state for a minimum of 10 h. This research gives a simple effective resolution in designing affordable and useful overall water-splitting electrocatalysts.

Controllable synthesis of flower-like Mn-Co-P nanosheets as bifunctional electrocatalysts for overall water splitting

Developing cost-effective and binder-free bifunctional electrocatalysts to boost the hydrogen and oxygen evolution reactions are crucial for overall water splitting. In this work, three-dimensional hierarchical Mn-Co-P/NF electrodes on nickel foam are synthesized by electrodeposition and chemical vapor deposition (CVD) firstly. Provide an excellent and controllable synthesis method by controlling the electrodeposition time and phosphating temperature. The Mn-Co-P composite exhibits the characteristics of vertically grown porous nanosheets, which can effectively expose the active sites. Benefit from the rational design with in-situ growth of functional materials and the unique structure, the Mn-Co-P/NF presents excellent electrocatalytic activities and stability with lower overpotentials of 63 mV and 310 mV to deliver 10 mA cm−2 for hydrogen evolution reaction (HER) and 10 mA cm−2 for oxygen evolution reaction (OER), respectively. Moreover, when directly used as a positive electrode and a negative electrode to form an electrocatalytic device to complete the overall water splitting, Mn-Co-P/NF merely requires a small cell voltage of 1.70 V to obtain 20 mA cm−2. This work offers a controllable method to design and synthesize highly efficient and stable transition metal phosphide catalysts for overall water splitting and other catalytic fields.

Integration of Fe3O4 nanospheres and micropyramidal textured silicon wafer with improved photoelectrochemical performance

Silicon (Si)-based composites have attracted extensive attention for photoelectrochemical (PEC) application. Herein, micropyramidal textured Si wafer was constructed by wet chemical etching method. Hydrothermally synthesized Fe3O4 nanospheres were further deposited on the micropyramids by a simple dip-coating approach. The integrated Fe3O4 nanospheres and Si micropyramids (denoted as Fe3O4@SiMPs) revealed 20 times of higher PEC efficiency than planar Si wafer, without obvious photocurrent decay and crystalline structure change during chronoamperometry test. The greatly enhanced PEC performance of Fe3O4@SiMPs is largely attributed to the seamless integration of Si micropyramids and Fe3O4 nanospheres. The micropyramidal textured structure can enhance light absorption by reducing the surface reflectance and enhancing the light trapping effect. The micropyramids and Fe3O4 nanospheres on the surface of planar Si wafer offer more specific surface area for the contact of electrode with electrolyte. The Fe3O4 nanospheres not only protect the micropyramids from corrosion, but also accelerate the PEC kinetics by promoting charge transfer between the electrode and the electrolyte. This study can inspire the optimal design of Si wafer-based nanocomposites as efficient PEC catalysts for overall water splitting.

Improved Light Harvesting and Efficiency for Overall Water Splitting by Embedding TiO2 Transition Layer in GaP/Ga2O3/Ga2Se3 Multijunction Photocatalyst

Photocatalytic water splitting to generate hydrogen has attracted great attention due to its potential for conversion and storage of solar energy. To obtain high efficiency of water splitting under solar irradiation, the catalyst should have good enough absorption in the visible region, excellent charge transfer ability, and satisfied stability during the photoreaction. Herein, the significant absorption promotion of the catalyst to a longer wavelength is achieved by simultaneously in situ selenylation and phosphorization of Ga2O3. The formation of narrow‐bandgap Ga2Se3 and GaP layers makes the catalyst absorb visible light up to 640 from 282 nm. In addition, by embedding a TiO2 transition layer between Ga2O3 and Ga2Se3, better crystal match in the catalyst is accomplished, which leads to better structural stability and the formation of better charge transfer route. Compared with GaP/Ga2O3/Ga2Se3, the GaP/TiO2/Ga2O3/TiO2/Ga2Se3 photocatalyst exhibits a much higher photocatalytic H2 evolution activity and achieves a higher apparent quantum efficiency (≈4% at 430 nm). Moreover, the TiO2 transition layer also reduces the crystal mismatch between GaP and Ga2O3. Herein, the advantage of utilizing the transition layer in multijunction photocatalyst to increase the photocatalytic activity and strengthen the stability of the assembled catalyst for overall water splitting is demonstrated.

Core-shell structure Co3O4@NiCo LDH was used as a high efficiency catalyst for overall water splitting

High efficiency, low cost and stable electrocatalysts are very important for large scale applications of water splitting. Therefore, we report a core–shell nanostructure Co3O4@NiCo LDH catalyst with Co3O4 nanowires as the core and NiCo LDH nanosheets as the shell, which has better electrocatalytic performance in alkaline solution compared with pure Co3O4 and NiCo LDH. The as-prepared Co3O4@NiCo LDH catalyst displays excellent activity for the OER with only overpotential of 279 mV to drive the current density of 15 mA cm−2. In addition, it also exhibits prominent HER activity, only requiring a small overpotential of 113 mV at 10 mA cm−2. The synergistic effect from Co3O4 and NiCo LDH promotes the catalytic performance of electrocatalysts in overall water splitting systems, only requiring 1.66 V to reach the current density of 10 mA cm−2 in a two-electrode alkaline electrolyzer. At the same time, the catalytic performance of the electrode has no obvious change after long time working, demonstrating its outstanding stability.

Irregularly Shaped Mn2O3 Nanostructures with High Surface Area for Water Oxidation

Water oxidation is an energy-consuming, four-electron-transfer reaction and is essential for solar fuel production from water. Catalysts based on precious metals such as RuO2 and IrO2 show high efficiency for oxygen evolution reaction. However, these catalysts are less abundant and expensive. To date, earth-abundant water oxidation catalysts still exhibit less activity for water oxidation. Herein, we report the synthesis of high surface area Mn2O3 nanomaterials for an efficient photocatalytic water oxidation catalyst. The synthesis process involves three simple steps. In the first step, CaMnO3 is synthesized by the citrate-gel method. In the second step, CaMnO3 is transformed into freestanding layers of ε-MnO2 by selective removal of Ca2+. In the third step, these layers are converted into irregularly shaped two-dimensional Mn2O3 flakes (AD-Mn2O3) by calcination at 550 °C. These AD-Mn2O3 nanostructures show 4 times higher surface area (127 m2 g–1) when compared to the irregularly shaped Mn2O3 nanoparticles (CG-Mn2O3) synthesized by the citrate-gel method at the same temperature. The AD-Mn2O3 nanostructures show super hydrophilicity with a contact angle of zero degree. This material exhibits excellent photocatalytic water oxidation activity with a turnover frequency of 1.53 × 10–3 s–1, which is twice the activity shown by CG-Mn2O3. This study can help in developing an earth-abundant, cost-effective, efficient catalyst for overall water splitting.

In-situ growth of Fe–Co Prussian-blue-analog nanocages on Ni(OH)2/NF and the derivative electrocatalysts with hierarchical cage-on-sheet architectures for efficient water splitting

To design an efficient and cost-effective electrocatalyst based on Prussian blue and its analogs are a promising choice to realize energy transformation and storage via water-splitting. Herein, a facile and practical method is developed to in-situ grow Fe–Co Prussian-blue-analog (PBA) nanocages with an open hole in each face center on Ni(OH)2/NF substrate to form the hierarchical cage-on-plate structure. Furthermore, the Fe–Co PBA nanocages attached to Ni(OH)2/NF plates are hydrogenated and nitrogenized into FeCoNi/NF and FeCoNiN/NF electrodes, respectively. As-prepared electrodes successfully retain the 3D hierarchical micro-nano structures of Fe–Co PBA@Ni(OH)2/NF precursor and can be used as a bifunctional water-splitting catalyst for overall water splitting. Compared to FeCoNi/NF, FeCoNiN/NF shows more efficiency and durability in the electrolytic water splitting tests in alkaline media. For the FeCoNiN/NF electrocatalyst, ultralow overpotentials for hydrogen evolution reaction (HER) are only 56 and 290 mV at current densities of 10 and 500 mA cm−2. Meanwhile, overpotentials for oxygen evolution reaction (OER) are 267 and 374 mV at current densities of 50 and 500 mA cm−2. The FeCoNiN/NF electrode can act both the cathode and the anode for overall water splitting, this electrolyzer only requires a cell voltage of 1.492 V to afford a current density of 10 mA cm−2. This electrolyzer can stably deliver a viable high current density of 625 mA cm−2 for 40 h to meet the condition of industrial application.

2D porous molybdenum nitride/cobalt nitride heterojunction nanosheets with interfacial electron redistribution for effective electrocatalytic overall water splitting

Porous 2D Mo2N-CoxN heterojunction nanosheets have been constructed based on a new strategy of cutting ZIF-67 polyhedral in Na2MoO4 aqueous solution. The material can act effective bi-functional catalysts for overall water splitting.

Efficient overall water splitting catalyzed by robust FeNi3N nanoparticles with hollow interiors

Hollow FeNi3N nanoparticles derived from oxygen etching and nitridation of FeNi3 were demonstrated as efficient bi-functional catalysts for overall water splitting.

Construction of Fe-doped CoP with hybrid nanostructures as a bifunctional catalyst for overall water splitting.

Due to their open skeleton structures, adjustable active sites and homogeneous catalytic centers, PBA-based materials have promising applications in electrochemical water splitting. Herein, we report a PBA derived Fe0.25-CoP electrocatalyst with a hybrid nanostructure, which offered a large specific surface area and active sites for the HER and OER, respectively. The as-synthesized Fe0.25-CoP catalyst exhibits remarkable catalytic performance and durability at overpotentials of 262 mV for the OER and 111 mV for the HER, requiring a voltage of merely 1.57 V to achieve a current density of 10 mA cm-2 for the electrocatalytic water splitting process. The preeminent activity of Fe0.25-CoP was mainly ascribed to the framework structures of Co-PBA and appropriate doping of Fe3+ which regulated the electronic structures and morphology of Fe0.25-CoP. In addition, the partial phosphating strategy retained the active centers for the OER in Co-PBA, which were further enhanced by the catalysis of Fe3+. In short, the rational design and regulation of catalyst structures and compositions is a promising approach for the development of highly efficient water splitting catalysts.

In situ construction of pollen-petal-like heterostructured Co3O4–CeO2 on 3D FeNi3 foam as a bifunctional catalyst for overall water splitting

In situ construction of pollen-petal-like and heterostructured Co3O4–CeO2 on 3D FeNi3 foam as a bifunctional catalyst for overall water splitting.

Optimized hierarchical nickel sulfide as a highly active bifunctional catalyst for overall water splitting.

Rational design of non-noble metal electrocatalysts with high intrinsic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is extremely impressive for sustainable electrocatalytic water splitting systems. However, it still remains a major challenge to engineer bifunctional performance. Here, we put forward a highly efficient water electrolyzer based on Ni3S2-based materials. The hierarchical structure of Ni3S2 can be well regulated for optimizing the HER catalytic activity. The best c-Ni3S2/NF electrode exhibits a much smaller overpotential of 220 mV to reach the current density of 100 mA cm-2. Upon introducing Fe species onto the Ni3S2/NF electrode by a simple dipping/drying method, the intrinsic OER activity can be extremely improved. As a result, the Fe-c-Ni3S2/NF catalyst showed excellent catalytic activity for the OER, including an overpotential of 193 mV at 10 mA cm-2, high specific current density and excellent stability. Post-characterization studies proved that the remaining S anions have an effective influence on improving the OER intrinsic activity. The assembled water electrolyzer also presented superior performance, such as a very low cell voltage of 1.50 V at 10 mA cm-2 and excellent durability for 120 h in alkaline medium. This strategy provides a promising way to design highly active and low-cost materials for overall water electrolysis.

In situ formation of highly exposed NiPS3 nanosheets on nickel foam as an efficient 3D electrocatalyst for overall water splitting

Vertical NiPS3 nanosheets in situ grown on conducting nickel foam were fabricated by a facile one-step chemical vapor transport method and used as an efficient bifunctional catalyst for overall water splitting.