Crystalline-Amorphous Interface Coupling of Ni3S2/NiPx/NF with Enhanced Activity and Stability for Electrocatalytic Oxygen Evolution

The rational design of highly efficient and stable electrocatalysts for the oxygen evolution reaction (OER) is an urgent need but remains challenging for various sustainable energy systems. How to adjust the atomic structure and electronic structure of the active center is a key bottleneck problem. Accelerating the electron transfer process and the deep self-reconstruction of active sites could be a cost-effective strategy toward electrocatalytic OER catalyst development. Here, a crystalline-amorphous (c-a) coupled Ni₃S₂/NiP_x electrocatalyst self-supported on nickel foam with an intimate interface was developed via a feasible solvothermal-electrochemistry method. The coupling interface of the crystalline structure with high conductivity and amorphous structure with numerous potential active sites could regulate the electronic structure and optimize the adsorption/desorption of O-containing species, ultimately resulting in high OER catalytic performance. The obtained Ni₃S₂/NiP_x/NF presents a low OER overpotential of 265 mV to obtain 10 mA·cm^-2 and a small Tafel slope of 51.6 mV·dec^-1. Also, the catalyst with the coupled interface exhibited significantly enhanced long-term stability compared to the other two catalysts, with <5% decay in OER activity over 20 h of continuous operation, while that of Ni₃S₂/NF and NiP_x/NF decreased by about 30 and 50%, respectively. This study provides inspiration for other energy conversion reactions in optimizing the performance of catalysts by coupling crystalline-amorphous structures.

Spherical Ni3 S2 /Fe-NiPx Magic Cube with Ultrahigh Water/Seawater Oxidation Efficiency

The rational construction of earth-abundant and advanced electrocatalysts for oxygen evolution reaction (OER) is extremely desired and significant to seawater electrolysis. Herein, by directly etching Ni₃ S₂ nanosheets through potassium ferricyanide, a novel self-sacrificing template strategy is proposed to realize the in situ growth of NiFe-based Prussian blue analogs (NiFe PBA) on Ni₃ S₂ in an interfacial redox reaction. The well-designed Ni₃ S₂ @NiFe PBA composite as precursor displays a unique spherical magic cube architecture composed of nanocubes, which even maintains after a phosphating treatment to obtain the derived Ni₃ S₂ /Fe-NiP_x on nickel foam. Specifically, in alkaline seawater, the Ni₃ S₂ /Fe-NiP_x as OER precatalyst marvelously realizes the ultralow overpotentials of 336 and 351 mV at large current densities of 500 and 1000 mA cm^-2 , respectively, with remarkable durability for over 225 h, outperforming most reported advanced OER electrocatalysts. Experimentally, a series of characterization results confirm the reconstruction behavior in the Ni₃ S₂ /Fe-NiP_x surface, leading to the in situ formation of Ni(OH)₂ /Ni(Fe)OOH with abundant oxygen vacancies and grain boundaries, which constructs the Ni₃ S₂ /Fe-NiP_x reconstruction system responsible for the remarkable OER catalytic activity. Theoretical calculation results further verify the enhanced OER activity for Ni₃ S₂ /Fe-NiP_x reconstruction system, and unveil that the Fe-Ni₂ P/FeOOH as active origin contributes to the central OER activity.

Core-shell CuO@NiCoMn-LDH supported by copper foam for high-performance supercapacitors

The core-shell structured CuO@NiCoMn-LDH electrode was synthesized by wet chemistry, calcination, and electrodeposition. The synergistic effect of CuO nanowires and NiCoMn-LDH nanosheets has a significant enhancement effect on electrode materials. At the same time, the Mn content plays a decisive role in regulating and optimizing the morphology and electrochemical performance of electrode materials. The optimized CuO@NiCoMn-LDH, a binder-free electrode, exhibits excellent electrochemical performance. It displays a high specific capacity of 2.66 mA h cm^-2 (20.7 F cm^-2, 336.71 mA h g^-1) at 10 mA cm^-2 and satisfactory cycling stability (under a current density of 30 mA cm^-2, after 3000 cycles, the capacity retention rate is 94.82%). In addition, an asymmetric supercapacitor (ASC) is built using the CuO@NiCoMn-LDH electrode as the positive electrode and Fe₃O₄@C/CuO electrode as the negative electrode to demonstrate its practical applicability in energy storage devices. At a power density of 4.79 mW cm^-2, the ASC device can achieve a maximum energy density of 2.67 mW h cm^-2. Two ASC devices are used as the power source of the light emitting diode (LED), which can emit light continuously for 15 minutes, showing great potential in energy storage device applications.

Synergistic mechanism of Ni(OH)2/NiMoS heterostructure electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all pH ranges

Designing and fabricating efficient electrocatalysts is a practical step toward the commercial application of the efficient hydrogen evolution reaction (HER) over all pH ranges. Herein, novel Ti@Ni(OH)₂-NiMoS heterostructure with interface between crystalline Ni(OH)₂ and amorphous NiMoS was rationally designed and fabricated on Ti mesh (denoted as Ti@Ni(OH)₂-NiMoS). Acid etching and calcination experiments helped in accurate elucidation of the synergistic mechanism as well as the vital role on crystalline Ni(OH)₂ and amorphous NiMoS. In acidic solutions, the HER performance of Ti@Ni(OH)₂-NiMoS was mainly attributed to the amorphous NiMoS. In neutral, alkaline, and natural seawater solutions, the HER performance was mainly determined by the synergistic interface behaviors between the Ni(OH)₂ and NiMoS. The crystalline Ni(OH)₂ accelerated water dissociation kinetics, while the amorphous NiMoS provided abundant active sites and allowed for fast electron transfer rates. To deliver current densities of 10 mA·cm^-2 in acidic, neutral, alkaline, and natural seawater solutions, the Ti@Ni(OH)₂-NiMoS required overpotentials of 138, 198, 180 and 371 mV, respectively. This paper provides general guidelines for designing efficient electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all-pH ranges.

Recent developments of Co3O4-based materials as catalysts for the oxygen evolution reaction

The demand for the development of clean and efficient energy is becoming increasingly pressing due to depleting fossil fuels and environmental concerns.

Heteroatom-doped carbon materials derived from covalent triazine framework@MOF for oxygen reduction reaction

Heteroatoms-doped carbon catalysts are ideal ways to promote the kinetic process of oxygen reduction reaction (ORR) due to their high energy conversion efficiency. Here, we report a series of catalysts...

In Situ Growth of S-Incorporated CoNiFe(oxy)hydroxides Nanoarrays as Efficient Multifunctional Electrocatalysts

Ni-, Co-based (oxy)hydroxides have received considerable attention as promising electrocatalysts for oxygen evolution reaction (OER), urea oxidation reaction (UOR), and even overall urea/water splitting. Constructing catalysts with special morphological and...

Boosting the charge transfer of FeOOH/Ni(OH)2 for excellent oxygen evolution reaction via Cr modification

For the electrocatalytic oxygen evolution reaction (OER) in alkaline media, there is an urgent need to optimize the adsorption strength of OH*. Here, a flower-like hybrid of Cr-doped FeOOH/Ni(OH)2 was used as an OER catalyst with a low overpotential of 291 mV at 50 mA cm-2. The results showed that faster charge transfer was achieved at the electrode/solution interface during the OER process after the FeOOH/Ni(OH)2 was modified by Cr, which facilitates the rate-determining step of the Volmer reaction. Furthermore, the results of faradaic efficiency and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the synergistic effect between the ternary metal and oxygen vacancies led to excellent OER performance. This work provides a new strategy for the preparation of high-efficiency and low-cost oxygen evolution electrocatalysts.

Facile formation of Fe-doped NiCoP hollow nanocages as bifunctional electrocatalysts for overall water splitting

Rational design of electrocatalysts with unique morphological structures and chemical compositions is crucial for electrochemical performance and energy storage capacity.

The latest development of CoOOH two-dimensional materials used as OER catalysts

The influence of the structure–activity relationship of the two-dimensional CoOOH catalyst on the OER is analyzed from different angles.