High-efficiency Oxygen Evolution Reaction Research Articles

In-situ growing low-crystalline Co9S8[sbnd]Ni3S2 nanohybrid on carbon cloth as a highly active and ultrastable electrode for the oxygen evolution reaction

The highly active electrodes for the oxygen evolution reaction (OER) are vital for boosting the overall efficiency of electrocatalytic water splitting to produce hydrogen fuel. Here we demonstrate a facile in-situ sulfurization strategy to construct an additive-free electrode with low-crystalline Co9S8Ni3S2 nanohybrid under the joint effects of fast sulfurization and lattice-mismatched growth. The Co9S8Ni3S2 nanohybrid exhibits semi-spherical architecture constructed with interconnected nanoflakes, and contains mesopores with an average pore size of 12.66 nm. The crystalline degrees of Ni3S2 and Co9S8 in the nanohybrid are estimated to be as low as 18.66% and 5.46%, respectively. For OER in 1 M KOH, the electrode attains a benchmark of 10 mA cm−2 at a very low overpotential (η10) of 220 mV and impressively demonstrates the outstanding OER stability lasting for 900 h at about 50 mA cm−2, which highlights its great potential applications in water splitting devices. More importantly, this work discloses the crucial contribution from low-crystalline Co9S8Ni3S2 nanohybrid to the high-efficiency OER, the key role of dynamic balance related to electroctatalytic activity in sustaining the ultralong-term stability, and the mechanisms behind the matter evolutions from Co9S8Ni3S2 into CoOOHNiOOH species.

Synergistic Effect of Bimetallic Sulfide Synthesized by a Simple Solvothermal Method for High-Efficiency Oxygen Evolution Reaction

Synergistic Effect of Bimetallic Sulfide Synthesized by a Simple Solvothermal Method for High-Efficiency Oxygen Evolution Reaction

Low-cost high entropy alloy (HEA) for high-efficiency oxygen evolution reaction (OER)

Low-cost high entropy alloy (HEA) for high-efficiency oxygen evolution reaction (OER)

Microwave rapid hydrolysis induced two-dimensional NiFeSe nanosheets for efficient oxygen evolution reaction

The key to the development of renewable energy is to search a cheap and efficient non-precious metal based oxygen evolution reaction (OER) electrocatalyst. The NiFe-based catalyst showed excellent catalytic properties. Herein, nickel-iron selenide (m-NiFeSe) with a two-dimensional nanosheet structure was prepared by using the nickel foam as the substrate and the electrodeposition-microwave rapid hydrolysis method. The presence of microwave not only changes the microscopic morphology, forms a new catalytic interface, increases the active area, but also appears mixed valence states of nickel (Ni2+/Ni3+) and high valence states of selenium, which makes the catalyst possess excellent basic OER electrocatalytic performance. In addition, the synergistic effect between nickel metal and iron metal is also one of the reasons for the improved property. Finally, the microwave-assisted catalysts reached electric current densities of 10 and 100 mA·cm−2 at overpotentials of 128 and 291 mV, separately, and had good durability in the chronopotentiometry test at a current density of 100 mA·cm−2 for 18 h. The purpose of this study is to provide a simple and feasible method for the preparation of inexpensive and high-efficiency OER electrocatalysts.

Black phosphorus nanoflakes decorated hematite photoanode with functional phosphate bridges for enhanced water oxidation

Black phosphorus (BP) as a promising two-dimension semiconductor has been widely investigated for energy storage and conversion. Herein, a heterostructure photoanode by integrating BP nanoflakes and hematite was fabricated, in which the functional phosphate by the partially oxidation of BP could tightly bridge hematite and BP and improve the interfacial charge transfer. The well-matched band structures of BP and hematite, as well as the highly-efficient oxygen evolution reaction (OER) activity of BP can significantly facilitate the charge separation and transfer for enhanced water oxidation performance. As a result, the as-prepared heterostructure exhibits a high photocurrent density of 3.02 mA cm−2 at 1.23 V vs. RHE, much better than that of the sample without BP modification. Furthermore, a remarkable photocurrent density of 3.81 mA cm−2 at 1.23 V vs. RHE with good photostability can be achieved after the loading of FeNiOOH cocatalyst. This study clearly shows the excellent application of BP for solar water splitting.

Porous Mn-doped cobalt phosphide nanosheets as highly active electrocatalysts for oxygen evolution reaction

Transition metal phosphides (TMP) show great potential to alternative noble metal based electrocatalysts for oxygen evolution reaction (OER) electrolysis but the still unsatisfactory catalytic activity hinders its practical application. Therefore, it is of much significance to rationally design TMP electrocatalysts for achieving high-efficiency OER. Here, we design Mn-doped cobalt phosphide (Mn-CoP) porous nanosheets for highly active OER through the in-situ metal acetate hydroxide transformation and subsequent phosphidation treatment. Benefiting from synergistic effects of the porous structure, high density of active sites and improved charge-transfer capability, the optimized Mn-CoP serving as a pre-catalyst shows an impressive alkaline OER performance with a low overpotential of 288 mV at the current density of 10 mA cm−2 and high stability. Post-electrolysis characterizations show the conversion from Mn-CoP to vertical Mn-CoOOH hexagonal nanosheets during OER, in which the transformed Mn-CoOOH not only provide extra active sites, but serve as the highly active species. Density functional theory (DFT) calculations reveal that Mn doping can increase the gap states near the Fermi level of active O sites, endowing facilitated deprotonation of OH* to O* and reducing the energy barrier of rate-determining step. This protocol provides a novel insight for the construction of highly efficient TMP water oxidation electrocatalysts.

Cathodic plasma driven self-assembly of HEAs dendrites by pure single FCC FeCoNiMnCu nanoparticles as high efficient electrocatalysts for OER

High-entropy alloys (HEAs) have been recognized as promising catalysts enabling the improvement of the sluggish kinetics of oxygen evolution reaction (OER). Nevertheless, the fabrication of nano HEAs at large-scale is still challenging. Herein, for the first time to the best of our knowledge, cathodic plasma electrolysis deposition (CPED) is utilized to develop FeCoNiMnCu HEA dendrites which are self-assembled by single HEA nanoparticles. These particles were examined to be face-centered cubic, having a size less than 40 nm and being randomly stacked together porously. The dendrites appear a 3D structure and leave a gap of approximately 5 um in between, leading to a significantly large surface area. Along with the highly deformed lattices with defects, this unique nanostructure achieves the very high efficient OER performance with an overpotential of 280 mV at 10 mA cm−2 and a low Tafel slope of 59 mV dec−1 in 1.0 M KOH solution. FeCoNiMnCu HEA dendrites also show outstanding electrochemical stability and are claimed that no compositional reorganization occurs after the long-term durability test. This work provides a new route to synthesize nanoscale HEAs for energy storage and conversion in a large-scale base for practical commercialization.

Local electronic structure modulation of NiVP@NiFeV-LDH electrode for high-efficiency oxygen evolution reaction

The emergence of alternative sustainable energy technologies has stimulated the utilisation of high-efficiency, cost-effective electrodes for renewable energy conversion. The oxygen evolution reaction (OER) is critical for water splitting and rechargeable metal-air batteries. However, the identification of efficient and robust non-noble-metal-based OER electrocatalysts remains a major hurdle for large-scale hydrogen production. Herein, NiVP@NiFeV-LDH heterojunction catalysts were constructed by phosphidation and hydrothermal processing, because OER activity can be improved by coupling NiVP and NiFeV-LDH. NiVP@NiFeV-LDH/NF exhibited remarkable OER performance with an ultralow overpotential of 317 mV at a current density of 100 mA cm−2 and a Tafel slope of 83.0 mV dec−1 in an alkaline environment. The high efficiency of NiVP@NiFeV-LDH/NF is attributed to increased mass and electron transport because of array structure formation and interfacial electronic structure optimisation, respectively. This work provides a novel approach for augmenting the OER performance of non-noble-metal-based electrocatalysts for energy conversion applications.

Encapsulation of Janus-structured Ni/Ni2P nanoparticles within hierarchical wrinkled N-doped carbon nanofibers: Interface engineering induces high-efficiency water oxidation

The exploration of efficient and economical electrocatalysts towards the oxygen evolution reaction (OER) is highly imperative for the development of OER-associated sustainable energy technologies. Interface engineering-enabled electronic regulation represents a powerful leverage to improve the intrinsic activity of earth-abundant electrocatalysts. Herein, we report a scalable hydroxycarbonate-assisted pyrolysis strategy to immobilize Janus-structured fine Ni/Ni2P nanoparticles onto hierarchical N-doped carbon nanosheet-grafted nanofibers (denoted as Ni/Ni2P@N-CNF hereafter) for high-efficiency electrocatalytic OER. The strong coupling of fine Ni/Ni2P hetero-nanoparticles with the superstructured carbon substrate renders Ni/Ni2P@N-CNF with regulated electronic state, sufficient anchored active sites, shortened distance for mass transport and enhanced structural stability. Consequently, the optimized Ni/Ni2P@N-CNF exhibits extraordinary electrocatalytic OER activity and durability in KOH medium. As a proof-of-concept demonstration, when pairing Ni/Ni2P@N-CNF with commercial Pt/C catalyst for overall water splitting, the assembled two-electrode electrolyzer outperforms the state-of-the-art RuO2‖Pt/C-equipped counterpart. The concept of interface engineering and carbon hybridization herein may provide new inspirations for the future design of affordable and efficient electrocatalysts for various sustainable energy conversions.

Interface engineering of porous Fe2P-WO2.92 catalyst with oxygen vacancies for highly active and stable large-current oxygen evolution and overall water splitting

Constructing a low cost, and high-efficiency oxygen evolution reaction (OER) electrocatalyst is of great significance for improving the performance of alkaline electrolyzer, which is still suffering from high-energy consumption. Herein, we created a porous iron phosphide and tungsten oxide self-supporting electrocatalyst with oxygen-containing vacancies on foam nickel (Fe2P-WO2.92/NF) through a facile in-situ growth, etching and phosphating strategies. The sequence-controllable strategy will not only generate oxygen vacancies and improve the charge transfer between Fe2P and WO2.92 components, but also improve the catalyst porosity and expose more active sites. Electrochemical studies illustrate that the Fe2P-WO2.92/NF catalyst presents good OER activity with a low overpotential of 267 mV at 100 mA cm−2, a small Tafel slope of 46.3 mV dec−1, high electrical conductivity, and reliable stability at high current density (100 mA cm−2 for over 60 h in 1.0 M KOH solution). Most significantly, the operating cell voltage of Fe2P-WO2.92/NF || Pt/C is as low as 1.90 V at 400 mA cm−2 in alkaline condition, which is one of the lowest reported in the literature. The electrocatalytic mechanism shows that the oxygen vacancies and the synergy between Fe2P and WO2.92 can adjust the electronic structure and provide more reaction sites, thereby synergistically increasing OER activity. This work provides a feasible strategy to fabricate high-efficiency and stable non-noble metal OER electrocatalysts on the engineering interface.

High-valent Zirconium-doping modified Co3O4 weave-like nanoarray boosts oxygen evolution reaction

It is urgently crucial to design high-performance and low-cost electrocatalysis for oxygen evolution reaction (OER) toward associated renewable energy systems. Herein, we reported that a certain amount of Zirconium doping in Co3O4 can regulate the electronic structure and morphology, therefore, boost the OER electrocatalytic performance. Zr doped Co3O4 demonstrates more excellent OER activity than pure Co3O4, as confirmed by density functional theory (DFT) calculations and experimental results, where the acceleration of potential rate-determining step and the improvement of conductivity are attributed to the introduction of Zr-dopants. Specifically, the as-synthesized 3D Zr-Co3O4/NF exhibits prominent OER activity with low overpotential 307 mV to drive current density of 20 mA cm−2, modest Tafel slope of 99 mV dec−1 and robust stability in 1 M KOH electrolyte. Our work reveals a novel approach to disclose Zr as a feasible dopant to optimize electronic structure and OER catalytic performance of metal oxides, and also proves the guiding role of DFT calculations for reasonable preparation of high-efficiency OER catalysts.

Oxygen vacancies and V co-doped Co3O4 prepared by ion implantation boosts oxygen evolution catalysis* *Project supported by the National Natural Science Foundation of China (Grant Nos. 12025503, U1867215, and U1932134), Hubei Provincial Natural Science Foundation (Grant No. 2019CFA036), the Fundamental Research Funds for the Central Universities, China (Grant No. 2042020kf0211), and China Postdoctoral Science Foundation (Grant No. 2020M682429).

Introducing heteroatoms and defects is a significant strategy to improve oxygen evolution reaction (OER) performance of electrocatalysts. However, the synergistic interaction of the heteroatom and defect still needs further investigations. Herein, we demonstrated an oxygen vacancy-rich vanadium-doped Co3O4 (V–Ov–Co3O4), fabricated by V-ion implantation, could be used for high-efficient OER catalysis. X-ray photoelectron spectra (XPS) and density functional theory (DFT) calculations show that the charge density of Co atom increased, and the reaction barrier of reaction pathway from O* to HOO* decreased. V–Ov–Co3O4 catalyst shows a low overpotential of 329 mV to maintain current density of 10 mA⋅cm−2, and a small Tafel slope of 74.5 mV⋅dec−1. This modification provides us with valuable perception for future design of heteroatom-doped and defect-based electrocatalysts.

Structure optimization and electronic modulation of sulfur-incorporated cobalt nanocages for enhanced oxygen evolution

Cobalt-based oxides and hydroxides have always been one of the optimal catalysts for Oxygen Evolution Reaction (OER) in alkaline environment in recent years. However, it remains a challenge for simple cobalt oxides such as CoO, Co3O4 and CoOOH to provide high catalytic activity both with ideal conductivity and stability. Herein, we prepared a new type of sulfur-incorporated cobalt oxide nanocages as high efficiency OER catalyst using Co-MOF as precursor. With the help of sodium sulfide, one step water-warm immersion-alcohol refluxing method can achieve the cavitation of precursors and uniform incorporation of sulfur atoms meanwhile. The hollow cubic structure constructed by fluffy nanosheets is beneficial to the exposure of active sites, the regulation of electronic structure and improve the electron transfer speed. After electrochemical testing, the prepared CoS@CoO showed outstanding OER activity compared with other cobalt-based catalysts. More importantly, this material has also withstood the electrochemical test of long range due to the stable structural foundation provided by Co-MOF. This work comes up with a new idea for OER activity promotion of hollow doped cobalt-based catalysts through morphology control and electronic structure optimization.

Regulating the electronic structure of NiFe layered double hydroxide/reduced graphene oxide by Mn incorporation for high-efficiency oxygen evolution reaction

The development of highly efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts for renewable energy systems is vitally essential. Modulation of the electronic structure through heteroatom doping is considered as one of the most potential strategies to boost OER performances. Herein, a rational design of Mn-doped NiFe layered double hydroxide/reduced graphene oxide (Mn-NiFe LDH/rGO) is demonstrated by a facile hydrothermal approach, which exhibits outstanding OER activity and durability. Experimental results and density functional theory (DFT) calculations manifest that the introduction of Mn can reprogram the electronic structure of surface active sites and alter the intermediate adsorption energy, consequently reducing the potential limiting activation energy for OER. Specifically, the optimal Mn-NiFe LDH/rGO composite shows an enhanced OER performance with an ultralow overpotential of 240 mV@10 mA cm−2, Tafel slope of 40.0 mV dec−1 and excellent stability. Such superior OER activity is comparable to those of the recently reported state-of-the-art OER catalysts. This work presents an advanced strategy for designing electrocatalysts with high activity and low cost for energy conversion applications.

A Novel Phosphide Derived From Metal-Organic Frameworks as Cost-Effective Electrocatalyst for Oxygen Evolution Reaction

Abstract Developing an efficient, green, and low-cost non noble metal catalyst toward oxygen evolution reaction (OER) has been urgent for new generation of sustainable energy technologies. Herein, the Co/Ni metal-organic frameworks (MOFs) derived metal phosphides/carbon matrix composites are successfully produced by the precipitation-carbonization-phosphorization processes. The obtained samples are characterized and analyzed for structural and morphological investigation. Electrochemical tests for OER are performed in the alkaline medium. The positive effects of P, Ni doping in MOFs on the structure and properties of composites have been analyzed. Benefitting from the unique structure of three-dimensional flower-like polyhedron with rich structure and higher porosity, the NiCo-P/NC catalyst exhibits the lowest overpotential of 0.32 V compared with the commercial IrO2 (0.34 V) at 10 mA/cm2, as well as outstanding stability and kinetic mechanism. Besides, the cost of the proposed novel material is calculated to be 4.337 US$/g, which is only 1.57% of that of commercial IrO2 (276 US$/g). The results obtained from the MOF-derived low-cost and high-efficiency OER catalyst would provide a new perspective on application of electrochemical storage and batteries.

Engineering unique Fe(SexS1−x)2 nanorod bundles for boosting oxygen evolution reaction

Fe-based electrocatalysts have attracted significant attention on account of the possibility for the realization of low-cost, high efficiency, and stable oxygen evolution reaction (OER) in alkaline solution. In this study, we present a new type of Fe(SexS1−x)2 nanorod bundles, which were successfully synthesized via a simple one-step hydrothermal method. We further demonstrate the applicability of these structures as electrocatalysts for OER application. We reveal that the incorporation of S into FeSe2 cause lattice strain and lattice defect, which is beneficial to expose more active sites and optimize the electronic structure, and hence the Fe(SexS1−x)2 composites display favorable catalytic for OER. More interestingly, the as-prepared Fe(Se0.5S0.5)2 catalyst exhibits the best OER performance with an overpotential at 10 mA·cm−2 of 247 mV, a low tafel slope of 54 mV/dec, and excellent catalytic stability. This work is expected to open a new door to discover other Fe-based materials as efficient catalysts for renewable energy.

Vertically-interlaced NiFeP/MXene electrocatalyst with tunable electronic structure for high-efficiency oxygen evolution reaction

Layered double hydroxides (LDHs) with decent oxygen evolution reaction (OER) activity have been extensively studied in the fields of energy storage and conversion. However, their poor conductivity, ease of agglomeration, and low intrinsic activity limit their practical application. To date, improvement of the intrinsic activity and stability of NiFe-LDHs through the introduction of heteroatoms or its combination with other conductive substrates to enhance their water-splitting performance has drawn increasing attention. In this study, vertically interlaced ternary phosphatised nickel/iron hybrids grown on the surface of titanium carbide flakes (NiFeP/MXene) were successfully synthesised through a hydrothermal reaction and phosphating calcination process. The optimised NiFeP/MXene exhibited a low overpotential of 286 mV at 10 mA cm−2 and a Tafel slope of 35 mV dec−1 for the OER, which exceeded the performance of several existing NiFe-based catalysts. NiFeP/MXene was further used as a water-splitting anode in an alkaline electrolyte, exhibiting a cell voltage of only 1.61 V to achieve a current density of 10 mA cm−2. Density functional theory (DFT) calculations revealed that the combination of MXene acting as a conductive substrate and the phosphating process can effectively tune the electronic structure and density of the electrocatalyst surface to promote the energy level of the d-band centre, resulting in an enhanced OER performance. This study provides a valuable guideline for designing high-performance MXene-supported NiFe-based OER catalysts.

One-step hydrothermal synthesized 3D P–MoO3/FeCo LDH heterostructure electrocatalysts on Ni foam for high-efficiency oxygen evolution electrocatalysis

Low-cost yet high-efficiency oxygen evolution reaction (OER) catalysts have attracted ardent attention to speed up the development of water electrolysis. Recent researches have shown that layered double hydroxides (LDH) are promising candidates towards OER, but further improvement is still highly demanded for its large-scale practical application in water splitting. Herein, we report a 3D P-doped MoO3/FeCo LDH/NF (P–MoO3/FeCo LDH/NF) ultrathin nanosheet heterostructure electrocatalyst with an extremely low overpotentials of 225 mV for delivering a current density of 10 mA cm−2 for OER and a great durability for at least 80 h by a simple one-step hydrothermal method. Extraordinarily, the P–MoO3/FeCo LDH catalyst achieves a high current density of 300 mA cm−2 and even 350 mA cm−2 at an extremely low overpotential of 297 mV and 302 mV, respectively, which is crucial for the water electrolysis industry. The remarkable performance may be attributed to that the heterostructure between P–MoO3 and FeCo LDH not only optimizes electronic structure, thus inducing electron transfer from P–MoO3 to FeCo LDH and then realizing fast electron transfer rates, but also produces more catalytic active sites. Moreover, the synergetic effect between MoO3 and FeCo LDH also plays an essential role for enhancing the catalytic performances. This work explores the effect of phosphomolybdic acid on the structure, composition and performances of FeCo LDH catalysts, and also provides a simple and cost-effective way to prepare high-efficiency and low-cost layered double hydroxide electrocatalysts for OER.

Synergistic coupling of NiFe layered double hydroxides with Co-C nanofibers for high-efficiency oxygen evolution reaction

In recent years, the design of high-performance and low-cost electrocatalysts for oxygen evolution reaction (OER) has captured great interest in the field of energy conversion and storage. Layered double hydroxide (LDH) with special configuration usually shows a highly electrochemical activity and become a desirable functional material for OER. In this work, carbon nanofibers embedded with Co nanoparticles have been prepared via an electrospinning and carbonization process, which can be served as a conductive support for the growth of NiFe LDH nanosheets through an electrodeposition route to produce a hierarchical 3D structure (denoted as 3D core-shell Co-C@NiFe LDH nanofibers). Owing to the high conductivity, large surface area and strong electron transfer between NiFe LDH nanosheets and Co-C nanofibers, the as-prepared 3D core-shell Co-C@NiFe LDH nanofibrous catalyst shows an excellent OER performance with an overpotential of only 249 mV at the current density of 10 mA cm−2 and a small Tafel slope of 57.9 mV dec−1, demonstrating an outstanding electrocatalytic activity for water oxidation. Furthermore, the 3D core-shell Co-C@NiFe LDH nanofibers also exhibit a superior long-term stability, with no obvious decrease in current density after nearly 190 h testing. Hence, the low-cost 3D core-shell Co-C@NiFe LDH nanofibrous electrocatalyst with an outstanding OER performance offers a novel chance for practical electrochemical water splitting application.

N-doped graphene anchored ultrasmall Ir nanoparticles as bifunctional electrocatalyst for overall water splitting

Seeking for extremely active and durable bifunctional electrocatalysts towards the overall water splitting possesses a strategic significance on the development of sustainable and clean energy for the replacement of fossil fuels. Ir-based nanomaterials are deemed as one of the most high-efficiency oxygen evolution reaction electrocatalysts while the hydrogen evolution reaction performance is unfavorable. In this work, we report a one-pot hydrothermal synthesis of N-doped graphene anchored Ir nanoparticles (Ir/N-rGO) with ultrasmall particle size (∼2.0 nm). Apart from the predictably superior OER performance, the resultant Ir/N-rGO also displays excellent hydrogen evolution reaction (HER) performance, requiring merely 76 and 260 mV overpotentials to achieve the current density of 10 mA cm−2 towards HER and OER, respectively. When applied as the bifunctional electrodes for overall water splitting, Ir/N-rGO needs a lower overpotential (1.74 V) to achieve a current density of 50 mA cm−2 in alkaline solution, exceeding that of Pt/C and RuO2 couple (1.85 V). Thus, the as-fabricated Ir/N-rGO has a commendable prospect in the practical application of alkaline water electrocatalysis.