Electrocatalytic OER Research Articles

An amorphous FeCoNiMnCr high-entropy alloy supported by 2H-MoS2 on carbon cloth as a highly efficient and robust electrocatalyst for water oxidation

Novel electrocatalysts with amorphous FeCoNiMnCr HEA supported by 2H-MoS2 on carbon cloth (FeCoNiMnCr@MoS2-CC) have been designed for OER electrocatalysis. Due to the synergistic effects of FeCoNiMnCr and 2H-MoS2, the FeCoNiMnCr@MoS2-CC electrocatalysts show significantly enhanced electrocatalytic performance for the OER and good stability.

Water coordinated Co-MOFs with 1D/2D network structure and highly enhanced electrocatalytic OER activity

Water coordinated cobalt-metal organic frameworks (Co-MOFs) exhibited network structure dependent strong electrocatalytic OER activity in alkaline medium.

Dual-cation doping precisely reducing the energy barrier of the rate-determining step for promoting oxygen-evolving activity

A sunflower-like Ir, Fe-codoped Co(OH)2catalyst assembled by nanosheets is designed for boosting electrocatalytic OER, where dual-cation doping can significantly decrease the energy barrier of the rate-determining step for OER.

Waste is the best: end-of-life lithium ion battery-derived ultra-active Ni3+-enriched β-Ni(OH)2 for the electrocatalytic oxygen evolution reaction

The recovery of Ni as Ni(DMG)2 and subsequently as Ni3+-rich β-Ni(OH)2 from spent LIBs is reported. The presence of Ni3+ in the as-synthesized β-Ni(OH)2 results in its exceptional electrocatalytic OER activity without any oxidative pre-treatment.

Three-dimensional porphyrin-based covalent organic frameworks withstptopology for an efficient electrocatalytic oxygen evolution reaction

A novel 3D porphyrin-based COF, with 2-fold interpenetratedstptopology and greatly enhanced electrocatalytic OER performance after post-metallization, was synthesized.

Enhancing the electrocatalytic OER activity of Co-MOFs through labile solvents coordination

The presence of labile solvent coordination in Co-MOF-1 exhibited improved electrocatalytic OER activity compared to Co-MOF-2 which showed only strong ligand coordination with the metal centre.

Electrocatalytic water oxidation of coral-like porous Zn-CoP nanohybrids synergistically inspired by photothermal and photoelectronic effects

This work reports a coral-like porous Zn-CoP nanohybrid with notable photothermal and photoelectronic effects, which improve electron migrate and reaction kinetics jointly, thereby contributing to superior electrocatalytic OER and OWS performances.

The boosting electrocatalytic OER and 4-nitrophenol oxidation over bimetallic ZIF-67/Fe2O3 p-n conjunction: Experiments and DFT calculations

In the Co/Cu-ZIF/Fe2O3 p-n junction, the electrons flow from n-type Fe2O3 to p-type bimetallic Co/Cu-ZIF, resulting in the band bending and inner electric field from positive Fe2O3 to negative Co/Cu-ZIF. The density function theory calculation uncovered that such an electronic property change could boost the water oxidation performance. Experiments reveal that the obtained Co/Cu-ZIF(1/1)/Fe2O3 heterojunction achieves a low overpotential of 273 mV and a small Tafel slope of 133.6 mV·dec-1 at 10 mA·cm-2 current density, which are significantly lower than that of monometallic Co-ZIF and FC substrate. Moreover, the p-n conjunction can promote the electrocatalytic degradation of 4-nitrophenol, and the removal rate reaches 80%, current efficiency (23.97%) and low energy consumption (79.5 Wh·L-1) at 50 mA·cm-2. Therefore, it is expected that MOFs-based p-n conjunction with modulation of electron configuration is a promising alternative to boost the electrochemical water oxidation.

Ru tailored hydrous cobalt phosphate as a rational approach for high-performance alkaline oxygen evolution reaction

The water splitting is an appealing approach to fulfil the demand of energy without any global concerns. The oxygen evolution reaction is one of way to achieve unlimited energy from water but the low stability, high energy required to drive the reaction (overpotential), complicated and unscalable synthesis method of expensive catalysis restricts its real time implementation into modern society. Herein this report, we suggested Ru-tailored hydrous cobalt phosphate and its concentration effect as a dopant to improve the catalytic properties. Electrocatalytic properties were studied via linear sweep voltammetry, chrono-potentiometric studies at a 10 mA/cm2 for 20 h, electrochemical active surface area, turnover frequency, and Tafel slope. Cobalt phosphate showed the connected-nanorods morphology, which is further tunned by increasing Ru-doping concentration, achieving various features from agglomerated nanorods sensitized with uniform nanoparticles on the micro-flower shapes consisting of interconnected nanorods sensitized with nanoparticles. The good electrocatalytic OER performance of 5% Ru-doped hydrous cobalt phosphate was achieved, exhibiting low overpotential up to 310 mV (vs. RHE) at 10 mA/cm2 besides a small Tafel slope of 62 mV/dec in 1 M KOH. As well, stable O2 evolution for a period of 20 h was shown. DFT calculation reveals that the Ru can increase electrical conductivity and promote OER activity, observed from Bader charge analysis, electron density difference, and OER Gibbs free energy. The EIS plot, ECSA, and TOF estimation disclose that the increased electrical conductivity, the improved ECSA, and the high intrinsic activity are together responsible for the good OER activity for 5%Ru–CoPO.

Flower-like Co3O4@NiFe-LDH nanosheets enable high-performance bifunctionality towards both electrocatalytic HER and OER in alkaline solution

Exploring highly active and cost-effective metal-based overall water splitting catalysts are crucial for the large-scale conversion of sustainable electrical energy to fuels, feedstocks and green economy. Here, a nickel foam-supported electrocatalyst consisting of a one-dimensional Co3O4 nanowire and two-dimensional NiFe-LDH nanosheets is reported. The optimized Co3O4@NiFe-LDH/NF catalyst affords 79 and 215 mV at 10 mA cm−2 for catalyzing the hydrogen and oxygen evolution reaction in 1.0 M KOH, which also exhibits quick reaction kinetics and excellent durability. The self-supported electrode only requires 1.58 V to afford 10 mA cm−2 with astonishing stability for water splitting. The linked interfacial nanostructure between NiFe-LDH and Co3O4, which supports the enhancement of the electronic structure and increases catalytic active sites, is primarily responsible for the electrode’s remarkable catalysis performance. The Co3O4@NiFe-LDH/NF as an ideal electrocatalyst lays forth a broad technique for synthesizing electrocatalytic materials for efficient and scalable water splitting.

Skeleton-coated CoCu-Based bimetal hollow nanoprisms as High-Performance electrocatalysts for oxygen evolution reaction

CoSx materials with high catalytic activity are considered as promising HER electrocatalysts, but their inherent low electrical conductivity and easy loss of active sites have greatly limited their applications in OER electrocatalysis. Herein, we present a convenient method to synthesize Co-Cu hollow nanoprisms after wrapping and calcining with trithiocyanuric acid (C3H3N3S3) (denoted N-Co-Cu-S-x HNs). The results showed that Cu doping modified the charge density of Co center, leading to the enhancement of the intrinsic activity of the Co3S4 active center, meanwhile wrapping trithiocyanuric acid on the surfaces and calcinating to form N-containing C skeleton as a flexible substrate to encapsulate the catalysts, which effectively protected the active sites inside the catalysts. Notably, the OER catalyst that was optimized by adjusting the metal ratio and controlling the trithiocyanuric acid incorporation exhibited a low overpotential of 306 mV under a current density of 10 mA cm−2 and showed a superior durability of more than 27 h. This work may provide some insights into the preparation of oxygen evolution reaction catalysts with excellent performance through doping transition metals and protecting the internal active sites strategies.

Doping vacancy synergy engineering: Ce-doped FeNi-Sx micro-succulent ameliorating electrocatalytic oxygen evolution performance

The co-control strategy of doping and vacancy has proved to be an effective and flexible approach in the development of efficient catalysts because of the synergistic regulation of electronic structure and active site number. Here, we synthesized an electrocatalyst with a special micromorphology of succulent plants. In addition, the doping of the rare earth element Ce with a large ionic radius in NiFe bimetallic sulfides is accompanied by a large number of vacancies. Ion doping synergistic with vacancy engineering improves the electrochemical intrinsic performance in the OER process and has enhanced electron transfer ability and electrochemical specific surface area, thus exhibiting high electrocatalytic OER performance, small Tafel slopes, ultralow overpotential of 294 mV at 100 mA cm−2 and 276 mV at 50 mA cm−2 and robust operating durability. Combined with DFT calculations, the role of Ce ions in the NiFe bimetallic sulfide system was revealed. This work not only provides a strategy for designing ion doping to enhance vacancy concentration but also constructs an efficient and stable oxygen evolution electrocatalyst system, which provides an alternative path for designing efficient electric and photocatalysts.

Defect-Rich NiO Nanosheet for Promoting Electrocatalytic OER and Oxidation of Chiral 2-Butanol

Defect-Rich NiO Nanosheet for Promoting Electrocatalytic OER and Oxidation of Chiral 2-Butanol

Surface/interface engineering for fabricating hierarchical Ir doped NiMoO4 covered by CoMn layered double hydroxide toward oxygen evolution reaction

Designing and fabricating outstanding electrocatalysts for anodic oxygen evolution reaction plays a key role in driving the earlier application of water splitting for large-scale hydrogen production. Surface/interface engineering is regarded as the most effective method for activating the active sites and modulating the electronic structure, which are two crucial factors determining the electrocatalytic performance. Herein, amorphous CoMn LDH ultrathin nanosheets doped by Ir are integrated with low-crystalline NiMoO4 nanorods (Ir-NiMoO4/Ir-CoMn LDH) to fabricate advanced hierarchical OER electrocatalysts. The optimized Ir-NiMoO4/Ir-Co3Mn2 LDH exhibits excellent OER performance as attested by an ultralow overpotential of 221 mV at the current density of 10 mA cm−2, as well as superb long-term durability. The intimate interface between NiMoO4 and Co LDH and modified electronic structure induced by Ir and Mn doping can greatly optimize the binding strength of between active sites and intermediated species, which improves the electrocatalytic OER performance. This study manifests how the synergistic surface/interface engineering design of nanomaterials boosts their catalytic activity.

In-situ growth of ruthenium-based nanostructure on carbon cloth for superior electrocatalytic activity towards HER and OER

The control in synthesis and composition plays a vital role in exploring cost-effective efficient electrocatalysts for water splitting. This paper reported a glycerol-assisted solvothermal strategy to synthesize Ru-based electrocatalyst (Ru-G/CC), in-situ growing Ru nanoparticles (NPs) on carbon cloth (CC). The optimal Ru-G/CC exhibits a boosted HER activity (overpotential of 40 mV @ 10 mA cm−2, Tafel slope 76 mV dec−1), surpassing benchmark 20 wt% Pt/C; experimental characterization and DFT calculations verified that Ru NPs with a mixed amorphous/crystalline structure in Ru-G/CC effectively decrease the reaction energy barrier in HER. Also, the hydrothermally derived Ru-H2O/CC-350 exhibited a high electrocatalytic OER activity (overpotential of 270 mV @ 10 mA cm−2, Tafel slope 63 mV dec−1), exceeding the commercial RuO2. This work provides a successful story via regulating synthetic parameters to design efficient and stable Ru-based electrocatalysts for water splitting.

(Digital Presentation) The New 2H Hexagonal Double Perovskite Ba2CoMnO6 As a Superior OER Catalyst in Alkaline Media

Climate change has stimulated great interest in developing clean and renewable energy conversion and storage solutions. Emerging technologies for solutions, like unitized regenerative fuel cells, metal-air batteries, and water electrolyzers, depend on the reliable catalyst materials suited for long-term application in alkaline environments[1]. In particular, the demanding reaction in these systems is the oxygen evolution reaction involving complex multielectron/proton transfer processes and thus sluggish kinetic.[2] At present, the state-of-the-art OER catalysts are IrO2 and RuO2. However, the high cost and scarcity of these materials severely prevent the wide-scale application of these systems.[3] Perovskite oxide (e.g., single perovskite expressed as ABO3) electrocatalysts are particularly considered next-generation OER catalysts due to their adjustable physicochemical properties and, as a consequence, their catalytic properties by substitution of ions in the A and B sites.[4] Via doping both at A and B site, double perovskite oxides structure can form (AA′B2O5+δ), which were shown to have stable structure during the OER due to proper O p-band center position relative to the Fermi level. The previous research shows that hexagonal perovskites exhibit enhanced catalytic activity rather than cubic or tetragonal perovskites, which is associated with the face-sharing octahedral unit. [5,6] In this work, we systematically investigate doping of parent La2CoMnO6 with Ba to tune the crystal structure and electronic structure. A series of the double perovskites with the chemical formula of La2-xBaxCoMnO6 (x = 0, 0.5, 1.5, 2) were fabricated via the modified Sol-Gel Pechini method. According to Goldschmidt tolerance factor, it is expected that when Ba amount increases in the A site, the crystal structure changes from cubic to hexagonal, which can contribute to electrocatalytic OER activity based above discussions. Furthermore, it is anticipated that increasing Ba content at the A site should result in higher valence state of transition metals due to stabilizing charge balance of the structure. It is widely reported that presence of higher valence state of transition metals is beneficial for OER.The crystal structure was confirmed by combining powder X-ray diffraction (XRD) patterns and selected area electron diffraction (SAED) patterns. The two-layer hexagonal structure of Ba2CoMnO6 (BCM) was further characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results show doping of Ba into parent La2CoMnO6 resulted in the hexagonal phase formation and BCM achieves a current density of 10 mA cm–2 at a low overpotential of 288 mV and has the highest intrinsic activity in the series of BaxLa2-xCoMnO6 (x = 0, 0.5, 1, 1.5, 2). Furthermore, BCM exhibits outstanding stability of 12 h in a 0.1 M KOH electrolyte. The electronic structure and surface work function values of the catalysts were examined with X-ray photoelectron spectroscopy (XPS). XPS analysis revealed that valence state of Co and Mn increases through Ba amount in the structure, indicating the double perovskite oxide charge balance is maintained. In addition to valence state analysis, we performed work function analysis of the catalysts tested in this work. The result shows work function of the series of BaxLa2-xCoMnO6 (x = 0, 0.5, 1, 1.5, 2) substantially decreases with Ba content. Here, we show that the high intrinsic activity of BCM is not only related with the hexagonal structure and also may be related with exhibiting lower work function value in the series. In addition, our approach presents a new strategy, air quenching method, to synthesize a phase pure 2H-hexagonal double perovskite oxide. [1] Y. Zhou, X. Guan, H. Zhou, K. Ramadoss, S. Adam, H. Liu, S. Lee, H. Shi, M. Tsuchiya, D. Fong and S. Ramanathan, Nature, 534, 231-234 (2016).[2] X. Cui, P. Ren, D. Deng, J. Deng and X. Bao, Energy & Environmental Science, 9, 123-129 (2016).[3] X. Qiu, Y. Zhang, Y. Zhu, C. Long, L. Su, S. Liu and Z. Tang, Advanced Materials, 33, 2001731 (2020).[4] W. Yin, B. Weng, J. Ge, Q. Sun, Z. Li and Y. Yan, Energy & Environmental Science, 12, 442-462 (2019).[5] L. Tang, W. Zhang, D. Lin, Y. Ren, H. Zheng, Q. Luo, L. Wei, H. Liu, J. Chen and K. Tang, Inorganic Chemistry Frontiers, 7, 4488-4497 (2020).[6] C. Chen, G. King, R. M. Dickerson, P. A. Papin, S. Gupta, W. R. Kellogg and G. Wu, Nano Energy, 13, 423-432 (2015).

Manipulating Spin Polarization of Defected Co3O4 for Highly Efficient Electrocatalysis

Electrocatalytic water splitting is limited by kinetics-sluggish oxygen evolution, in which the activity of catalysts depends on their electronic structure. However, the influence of electron spin polarization on catalytic activity is ambiguous. Herein, we successfully regulate the spin polarization of Co3O4 catalysts by tuning the concentration of cobalt defects from 0.8 to 14.5%. X-ray absorption spectroscopy spectra and density functional theory calculations confirm that the spin polarization of Co3O4 is positively correlated with the concentration of cobalt defects. Importantly, the enhanced spin polarization can increase hydroxyl group absorption to significantly decrease the Gibbs free energy change value of the OER rate-determining step and regulate the spin polarization of oxygen species through a spin electron-exchange process to easily produce triplet-state O2, which can obviously increase electrocatalytic OER activity. In specific, Co3O4-50 with 14.5% cobalt defects exhibits the highest spin polarization and shows the best normalized OER activity. This work provides an important strategy to increase the water splitting activity of electrocatalysts via the rational regulation of electron spin polarization.

New microporous nickel phosphonate derivatives N, P-codoped nickel oxides and N, O-codoped nickel phosphides: Potential electrocatalysts for water oxidation

The development of a highly efficient non-noble metal-based electrocatalyst is very challenging for oxygen evolution (OER) reactions. The construction of heteroatom doped transition metal-based phosphonate derivatives such as metal oxides and phosphides are a potential candidate for electrocatalytic OER. Herewith, newly designed microporous organic-inorganic hybrid nickel phosphonate (NiGLy) has been synthesized using N,N-Bis(phosphonomethyl)glycine, and nickel nitrate hexahydrate under simple hydrothermal reaction conditions. The heteroatom doped derivatives, i.e., N, P-codoped nickel oxide (NiO500, NiO700), and N, O-codoped nickel phosphide (NiP500, NiP700), have been obtained by direct pyrolysis of NiGLy at different temperatures under aerobic and inert atmospheres, respectively. Due to the high specific surface area and the presence of micropores, these materials have been explored in the electrocatalytic oxygen evolution reaction. Notably, among other as-synthesized electrocatalysts, N, P-codoped nickel oxide (NiO500) exhibits the outstanding electrocatalytic OER activity where the overpotential is found to be 284 mV and Tafel slope is 50.0 mV dec−1 in alkaline solution. Also, the as-synthesized NiO500 catalyst shows excellent stability up to 50 h time.

Magnetic Field Enhancing OER Electrocatalysis of NiFe Layered Double Hydroxide

Magnetic Field Enhancing OER Electrocatalysis of NiFe Layered Double Hydroxide

Epitaxially Grown Ru Clusters–Nickel Nitride Heterostructure Advances Water Electrolysis Kinetics in Alkaline and Seawater Media

The epitaxial heterostructure can be rationally designed based on the in situ growth of two compatible phases with lattice similarity, in which the modulated electronic states and tuned adsorption behaviors are conducive to the enhancement of electrocatalytic activity. Herein, theoretical simulations first disclose the charge transfer trend and reinforced inherent electron conduction around the epitaxial heterointerface between Ru clusters and Ni3N substrate (cRu‐Ni3N), thus leading to the optimized adsorption behaviors and reduced activation energy barriers. Subsequently, the defect‐rich nanosheets with the epitaxially grown cRu‐Ni3N heterointerface are successfully constructed. Impressively, by virtue of the superiority of intrinsic activity and reaction kinetics, such unique epitaxial heterostructure exhibits remarkable bifunctional catalytic activity toward electrocatalytic OER (226 mV @ 20 mA cm−2) and HER (32 mV @ 10 mA cm−2) in alkaline media. Furthermore, it also shows great application prospect in alkaline freshwater and seawater splitting, as well as solar‐to‐hydrogen integrated system. This work could provide beneficial enlightenment for the establishment of advanced electrocatalysts with epitaxial heterointerfaces.