A cost-efficient and stable oxygen evolution electrocatalyst is essential for improving energy storage and conversion efficiencies. Herein, 2D nanosheets with randomly cross-linked CoNi layered double hydroxide (LDH) and small CoO nanocrystals were designed and synthesized via in situ reduction and interfacedirected assembly in air. The formation of CoNi LDH/CoO nanosheets was attributed to the strong extrusion of hydrated metal–oxide clusters driven by the interfacial tension. The obtained loose and porous nanosheets exhibited low crystallinity due to the presence of numerous defects. Owing to the orbital hybridization between metal 3d and O 2p orbitals, and electron transfer between metal atoms through Ni–O–Co, a number of Co and Ni atoms in the CoNi LDH present a high +3 valency. These unique characteristics result in a high density of oxygen evolution reaction (OER) active sites, improving the affinity between OH– and catalyst, and resulting in a large accessible surface area and permeable channels for ion adsorption and transport. Therefore, the resulting nanosheets exhibited high catalytic activity towards the OER. The CoNi LDH/CoO featured a low onset potential of 1.48 V in alkaline medium, and required an overpotential of only 300 mV at a current density of 10 mA·cm–2, while displaying good stability in accelerated durability tests.
The activity and durability of electrocatalysts are important factors in their practical applications,such as electrocatalytic oxygen evolution reactions (OERs)used in water splitting cells and metal-air batteries.In this study,a novel electrocatalyst,comprising few-layered graphitic carbon (～5 atomic layers) encapsulated heazlewoodite (Ni3S2@C) nanoparticles (NPs),was designed and synthesized using a one-step solid phase pyrolysis method.In the OER test,the Ni3S2@C catalyst exhibited an overpotential of 298 mV at a current density of 10 mA·cm-2,a Tafel slope of 51.3 mV·dec-1,and charge transfer resistance of 22.0 Ω,which were better than those of benchmark RuO2 and most nickelsulfide-based catalysts previously reported.This improved performance was ascribed to the high electronic conductivity of the graphitic carbon encapsulating layers.Moreover,the encapsulation of graphitic carbon layers provided superb stability without noticeable oxidation or depletion of Ni3S2 NPs within the nanocomposite.Therefore,the strategy introduced in this work can benefit the development of highly stable metal sulfide electrocatalysts for energy conversion and storage applications,without sacrificing electrocatalytic activity. 相似文献
Developing low-cost,efficient,and stable non-precious-metal electrocatalysts with controlled crystal structure,morphology and compositions are highly desirable for hydrogen and oxygen evolution reactions.Herein,a series of phosphorus-doped Fe7S8 nanowires integrated within carbon (P-Fe7S8@C) are rationally synthesized via a one-step phosphorization of one-dimensional (1D) Fe-based organicinorganic nanowires.The as-obtained P-Fe7S8@C catalysts with modified electronic configurations present typical porous structure,providing plentiful active sites for rapid reaction kinetics.Density functional calculations demonstrate that the doping Fe7S8 with P can effectively enhance the electron density of Fe7S8 around the Fermi level and weaken the Fe-H bonding,leading to the decrease of adsorption free energy barrier on active sites.As a result,the optimal catalyst of P-Fe7S8-600@C exhibits a relatively low overpotential of 136 mV for hydrogen evolution reaction (HER) to reach the current density of 10 mA/cm2,and a significantly low overpotential of 210 mV for oxygen evolution reaction (OER) at 20mA/cm2 in alkaline media.The work presented here may pave the way to design and synthesis of other prominent Fe-based catalysts for water splitting via electronic regulation. 相似文献
Rational design and controlled fabrication of efficient and cost-effective electrodes for the oxygen evolution reaction (OER) are critical for addressing the unprecedented energy crisis.Nickel-iron layered double hydroxides (NiFe-LDHs) with specific interlayer anions (i.e.phosphate,phosphite,and hypophosphite) were fabricated by a co-precipitation method and investigated as oxygen evolution electrocatalysts.Intercalation of the phosphorus oxoanion enhanced the OER activity in an alkaline solution;the optimal performance (i.e.,a low onset potential of 215 mV,a small Tafel slope of 37.7 mV/dec,and stable electrochemical behavior) was achieved with the hypophosphite-intercalated NiFe-LDH catalyst,demonstrating dramatic enhancement over the traditional carbonate-intercalated NiFe-LDH in terms of activity and durability.This enhanced performance is attributed to the interaction between the intercalated phosphorous oxoanions and the edge-sharing MO6 (M =Ni,Fe) layers,which modifies the surface electronic structure of the Ni sites.This concept should be inspiring for the design of more effective LDH-based oxygen evolution electrocatalysts. 相似文献
High gravimetric energy density, earth-abundance, and environmental friendliness of hydrogen sources have inspired the utilization of hydrogen fuel as a clean alternative to fossil fuels. Hydrogen evolution reaction (HER), a half reaction of water splitting, is crucial to the low-cost production of pure H2 fuels but necessitates the use of electrocatalysts to expedite reaction kinetics. Owing to the availability of low-cost oxygen evolution reaction (OER) catalysts for the counter electrode in alkaline media and the lack of low-cost OER catalysts in acidic media, researchers have focused on developing HER catalysts in alkaline media with high activity and stability. Nickel is well-known as an HER catalyst and continuous efforts have been undertaken to improve Ni-based catalysts as alkaline electrolyzers. In this review, we summarize earlier studies of HER activity and mechanism on Ni surfaces, along with recent progress in the optimization of the Ni-based catalysts using various modern techniques. Recently developed Ni-based HER catalysts are categorized according to their chemical nature, and the advantages as well as limitations of each category are discussed. Among all Ni-based catalysts, Ni-based alloys and Ni-based hetero-structure exhibit the most promising electrocatalytic activity and stability owing to the fine-tuning of their surface adsorption properties via a synergistic nearby element or domain. Finally, selected applications of the developed Ni-based HER catalysts are highlighted, such as water splitting, the chloralkali process, and microbial electrolysis cell.
Developing cost-efficient electrocatalysts for oxygen evolution is vital for the viability of H2 energy generated via electrolytic water.Engineering favorable defects on the electrocatalysts to provide accessible active sites can boost the sluggish reaction thermodynamics or kinetics.Herein,Col-xS nanosheets were designed and grown on reduced graphene oxide (rGO) by controlling the successive two-step hydrothermal reaction.A belt-like cobalt-based precursor was first formed with the assistance of ammonia and rGO,which were then sulfurized into Col-xS by L-cysteine at a higher hydrothermal temperature.Because of the non-stoichiometric defects and ultrathin sheet-like structure,additional cobalt vacancies (V'Co) were formed/exposed on the catalyst surface,which expedited the charge diffusion and increased the electroactive surface in contact with the electrolyte.The resulting Col-xS/rGO hybrids exhibited an overpotential as low as 310 mV at 10 mA.cm-2 in an alkaline electrolyte for the oxygen evolution reaction (OER).Density functional theory calculations indicated that the V'Co on the Col-xS/rGO hybrid functioned as catalytic sites for enhanced OER.They also reduced the energy barrier for the transformation of intermediate oxygenated species,promoting the OER thermodynamics. 相似文献
Exploration of the relationship between electrocatalytic activities and their chemical valence is very important in rational design of high‐efficient electrocatalysts. A series of porous nickel sulfides hybridized with N and S co‐doped carbon nanoparticles (NixSy‐NSCs) with different chemical valences of Ni, Ni9S8‐NSCs, Ni9S8‐NiS1.03‐NSCs, and NiS1.03‐NSCs are successfully fabricated, and their electrocatalytic performances as oxygen evolution reaction electrocatalysts are systematically investigated. The NixSy‐NSCs are obtained via a two‐step reaction including a low‐temperature synthesis of Ni‐Cys precursor followed by thermal decomposing of the precursor in Ar atmosphere. By controlling the sulfidation process during the formation of NixSy‐NSCs, Ni9S8‐NSCs, Ni9S8‐NiS1.03‐NSCs, and NiS1.03‐NSCs are obtained, respectively, giving rise to the increase of high‐valence Ni component, and resulting in gradually enhanced oxygen evolution reaction electrocatalytic activities. In particular, the NiS1.03‐NSCs show an exceptional low overpotential of ≈270 mV versus reversible hydrogen electrode at a current density of 10 mA cm?2 and a small Tafel slope of 68.9 mV dec?1 with mass loading of 0.25 mg cm?2 in 1 m KOH and their catalytic activities remained for at least 10 h, which surpass the state‐of‐the‐art IrO2, RuO2, and Ni‐based electrocatalysts. 相似文献
