Nickel Foam Substrate Research Articles

Fabrication of bimetallic Co/Ni composite oxides on Ni-foam as a highly active monolithic membrane catalyst for the reduction of 4-nitrophenol

The development of highly active non-noble metal catalysts is the prerequisite for the practical application of the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4. In this work, inexpensive Co/Ni bimetallic composite oxide integral membrane catalysts with different metal-ion molar ratios towards 4-NP reduction were grown on the nickel foam (NF) substrate by a facile oxalate-pyrolysis method. Benefiting from the synergistic effect between Co and Ni elements, special crystalline phase of NiCo2O4 with high electron transfer capacity and uniform nanoflake array structure, the NF-based monolithic membrane catalyst with a Co/Ni molar ratio of 2:1 (Co2Ni1) exhibited the optimal activity for the catalytic reduction of 4-NP. A reduction ratio of 96.71% for 250 mL of 4-NP with an initial concentration of 15 mg/L could be reached within 25 min under the reaction conditions as follows: two pieces of Co2Ni1 catalytic membranes (20 × 40 mm2), 0.015 mol/L NaBH4 and a temperature of 25 °C. The corresponding kinetic reaction rate constant was 0.1410 min−1, which was 2.0 and 15.5 times higher than that of pure Co3O4 and NiO. Moreover, the activation energy, enthalpy and entropy for the reaction were calculated as 17.44 kJ/mol, 14.97 kJ/mol and −210.61 J•mol−1•K−1, respectively. Notably, the reduction rates of 4-NP remained at around 97% during thirteen consecutive catalytic runs, indicating the good reusability of the Co2Ni1 integral membrane catalyst. These results show that NF-based Co/Ni composite oxide membrane is a promising integral catalyst for converting of 4-NP into 4-AP owing to its excellent properties and easy recovery feature.

Investigating the Stability of Electrodeposited NiMo Alloy for Hydrogen Evolution Reaction in Alkaline Media

A lot of efforts have been devoted to develop highly active noble-metal-free catalysts for hydrogen production by water electrolysis.1,2 Nevertheless, the stability of such catalysts, yet equally important, is rarely touched. NiMo alloy is an emerging catalyst for hydrogen evolution reaction (HER) in alkaline media.3 In the present work, we studied the stability of NiMo alloy for HER under alkaline (1M KOH, Fe-free) conditions as a model catalyst. Using electrodeposition at room temperature, we deposited NiMo alloy onto nickel foam substrates. A long-term (20h) stability test at a fixed current density of -100 mA cm-2 was carried out using chronopotentiometry. Electrochemical active surface area (ECSA) and HER polarization curves were determined prior and after this stability test. Here, obvious activity loss is observed. The ECSA of NiMo catalyst after chronopotentiometry test increases by 10%. Thus, an obvious increase in the overpotential is observed upon normalizing the catalytic current with ECSA (Figure 1a). As further stability test 100 CV cycles at a scan rate of 100 mV s-1 from 0 to –350 mV vs. RHE were carried out, the catalysts then hold for 30 min at open circuit potential and again 100 CV cycles carried out. A clear drop in activity during the second 100 cycles is also observed here and especially at the higher current density of 60 mA cm-2 (Figure 1b). In summary, we found that NiMo, though active initially, loses its activity with time under HER conditions in alkaline media.References Vesborg, P. C. K.; Seger, B.; Chorkendorff, I. Phys. Chem. Lett. 2015, 6, 951– 957.Zou, X. X.; Zhang, Y. Soc. Rev. 2015, 44, 5148– 5180.Kuznetsov, V. V.; Gamburg, Y. D.; Zhulikov, V. V.; Krutskikh, V. M.; Filatova, E. A.; Trigub, A. L.; Belyakova, O. A. Electrochim. Acta 2020, 354, 136610. Figure 1

Zn2+-triggered synthesis of Ni2P/Ni12P5 microflower arrays for efficient alkaline overall water splitting

Designing a transition metal-based bifunctional electrocatalyst with a unique structure, excellent activity, and good stability for alkaline overall water splitting remains a challenge. Herein, a novel three-dimensional heterogeneous Ni2P/Ni12P5 microflower array (Zn-Ni2P/Ni12P5/NF) grown on nickel foam (NF) substrate was prepared by a Zn2+-triggered phosphating route. The Zn-doping enhances the electronic interaction with Ni and P atoms, and regulates the electronic structure, surface state, and microstructure of the catalyst, which greatly increases the catalytic active site and improves the electrochemical reaction area and electron transfer efficiency of Zn-Ni2P/Ni12P5/NF. The prepared Zn-Ni2P/Ni12P5/NF exhibits excellent HER and OER properties, for HER, high current densities of 500 and 1000 mA/cm2 can be driven with low overpotentials of only 315 and 367 mV in 1 M KOH. For OER, the overpotential is only 414 and 477 mV at industrial current densities of 500 and 1000 mA/cm2. In addition, the current density of 1000 mA/cm2 can be achieved with a voltage of only 2.10 V, and the electrode surface also exhibits hydrophilic (solid-liquid interface) and superaerophobic characteristics that are more conducive to the catalytic reaction. This work provides an effective strategy to prepare HER/OER bifunctional electrocatalysts for large-scale water splitting.

Preparation of Electrodes with β-Nickel Hydroxide/CVD-Graphene/3D-Nickel Foam Composite Structures to Enhance the Capacitance Characteristics of Supercapacitors.

Supercapacitors have the characteristics of high power density, long cycle life, and fast charge and discharge rates, making them promising alternatives to traditional capacitors and batteries. The use of transition-metal compounds as electrode materials for supercapacitors has been a compelling research topic in recent years because their use can effectively enhance the electrical performance of supercapacitors. The current research on capacitor electrode materials can mainly be divided into the following three categories: carbon-based materials, metal oxides, and conductive polymers. Nickel hydroxide (Ni(OH)2) is a potential electrode material for use in supercapacitors. Depending on the preparation conditions, two crystal phases of nickel hydroxide, α and β, can be produced. When compared to α-NiOH, the structure of β-Ni(OH)2 does not experience ion intercalation. As a result, the carrier transmission rate of α-Ni(OH)2 is slower, and its specific capacitance value is smaller. Its carrier transport rate can be improved by adding conductive materials, such as graphene. β-Ni(OH)2 was chosen as an electrode material for a supercapacitor in this study. Homemade low-pressure chemical vapor deposition graphene (LPCVD-Graphene) conductive material was introduced to modify β-Ni(OH)2 in order to increase its carrier transport rate. The LPCVD method was used to grow high-quality graphene films on three-dimensional (3D) nickel foam substrates. Then, a hydrothermal synthesis method was used to grow β-Ni(OH)2 nanostructures on the 3D graphene/nickel foam substrate. In order to improve the electrical properties of the composite structure, a high-quality graphene layer was incorporated between the nickel hydroxide and the 3D nickel foam substrate. The effect of the conductive graphene layer on the growth of β-Ni(OH)2, as well as its electrical properties and electrochemical performance, was studied. When this β-Ni(OH)2/CVD-Graphene/3D-NF (nickel foam) material was used as the working electrodes of the supercapacitor under a current density of 1 A/g and 3 A/g, they exhibited a specific capacitance of 2015 F/g and 1218.9 F/g, respectively. This capacitance value is 2.62 times higher than that of the structure without modification with a graphene layer. The capacitance value remains at 99.2% even after 1000 consecutive charge and discharge cycles at a current density of 20 A/g. This value also improved compared to the structure without graphene layer modification (94.7%).

Amorphous Ni(OH)2 -Ni3 S2 /NF nano-flower heterostructure catalyst promotes efficient urea assisted overall water splitting.

Urea assisted overall water splitting represents a cost-effective and efficient technology for hydrogen production, which not only obviates the generation of explosive H2 and O2 gas mixture but also minimizes the energy cost for the water splitting. In this study, we employed a one-pot hydrothermal method to directly synthesize Ni(OH)2 -Ni3 S2 /NF hybrid nanoflowers on a nickel foam (NF) substrate, resulting in efficient and stable bi-functional electrocatalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Under alkaline conditions, the Ni(OH)2 -Ni3 S2 /NF catalyst exhibits low voltage requirements of 1.346 V and -0.014 V vs. RHE with a current density of 10 mA cm-2 for UOR and HER, respectively. Furthermore, when employing the Ni(OH)2 -Ni3 S2 /NF catalyst as both anode and cathode for urea-assisted overall water splitting, it requires a cell voltage of merely 1.396 V with a current density of 10 mA cm-2 , which is notably lower than the voltage required for complete water decomposition at the same current density (1.568 V vs. RHE). The one-step synthesis of the Ni(OH)2 -Ni3 S2 /NF catalyst lays a foundation for further exploration of other transition metal complexes as dual-function electrocatalysts, enabling energy-efficient electrolytic hydrogen production and the treatment of urea-rich wastewater.

Controllable synthesis and super electrochemical stability of copper phosphide (Cu3P) nanosheets catalyst in nearly neutral electrolyte

The catalytic activity and stability of cost-effective and highly efficient bifunctional electrocatalysts are crucial for electrochemical water splitting. However, the use of strongly alkaline or acidic electrolytes, which are commonly employed, poses environmental concerns. Therefore, the development of efficient electrocatalysts that can operate stably in neutral or near-neutral electrolytes holds significant importance. In this study, a self-supporting Cu3P/NF electrode was fabricated using a two-step method, wherein metal phosphide Cu3P was grown on a nickel foam (NF) substrate. Notably, the Cu3P/NF electrode exhibits an unexpected enhancement in electrochemical activity and stability when operated in an electrolyte consisting of CuSO4 and Na2CO3. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on the Cu3P/NF electrode require overpotentials of 131 mV and 230 mV, respectively, to achieve a current density of 10 mA cm−2 and 50 mA cm−2. Moreover, the stability of the Cu3P/NF electrode for HER and OER is improved by 90.22 % and 74.54 %, respectively, with the inclusion of CuSO4 in the Na2CO3 electrolyte. The improved catalytic performance and stability of Cu3P/NF electrode with the addition of CuSO4 can be attributed to the prevention of Cu + oxidation through Cu2+ and the formation of a local H+ adsorption electric field by the SO42− electron cloud. These factors contribute to the enhanced electrocatalytic activity and stability of Cu3P. This work expands the efficient utilization of electrocatalysts in near-neutral electrolytes, which is of great value for the widespread application of electrocatalysts and environmental protection.

Facile fabrication of AgFeS2 nanostructure via hydrothermal route for supercapacitor application

This study presents the electrochemical performance of AgFeS2 as an electrochemical energy storage material, highlighting its notable attributes such as exceptional electrical conductivity and abundant availability. AgFeS2 nanostructure was successfully fabricated utilizing single-step hydrothermal technique. Physiochemical characterization and electrochemical characterization, are both performed on the synthesized AgFeS2 nanostructure. An AgFeS2 sample on a nickel foam substrate was used to investigate the capacitance property of the materials. The Ag and Fe ions provide a synergistic contribution to the redox process that accelerates the electrochemical efficacy of the supercapacitor. An AgFeS2 nanostructure in a three-electrode system's galvanometric charge-discharge (GCD) profile showed a large specific capacitance (Cs) of 555 F g−1 @ 1 A g−1 in the potential range of 0 to 0.7 V (Ag/AgCl) and capacitive retention of 87 % over 7000th in 2.0 M KOH. The symmetric analysis depends on the AgFeS2 electrode has a high CS of 331 F g−1 at 1 A g−1 in an aqueous 2.0 M KOH in a two- electrode system. The AgFeS2 electrode-based symmetric supercapacitor has a specific power of 0.261 W kg−1 and a specific energy of 45 Wh kg−1. The capacitive results indicates that the AgFeS2 electrode is potential candidate for supercapacitor applications and it can also be employed in various fields such as water splitting, water remediation and photocatalysis.

Water splitting by CoFeLDH@NiFeS nanoelectrocatalyst assisted urea electrooxidation reaction

In this paper, NiFeS@CoFeLDH nanostructure was synthesized for the first time by electrochemical method in two steps. In the first stage, the first layer of NiFeS was deposited on the nickel foam (NF) substrate, and in the second stage, the second layer of cobalt-iron layered double hydroxide (CoFeLDH)by controlling the electrodeposition condition was deposited on the first. The deposition time and potential were optimized. The optimized NiFeS@CoFeLDH coating on NF has promising hydrogen evolution reaction (HER) activity, which exhibits small overpotentials of − 191.5, and − 304.0, at the current densities of − 10, and − 100 mA. cm−2, respectively. Furthermore, the synthesized NiFeS@CoFeLDH electrocatalyst only needs 358 mV overpotentials to operate at a current density of 10 mA. cm−2 indicating its great performance for the urea oxidation reaction (UOR). The electrode stability was examined at an industrial scale current density of − 100 and 10 mA. cm−2 for HER and UOR respectively, which showed a very stable response for at least 10 h. The results showed that the simultaneous application of NiFeS and CoFeLDH electrocatalysts has a synergistic effect that increases the surface-to-volume ratio and improves the active sites. According to high performance for HER and UOR and also simple, fast, and binder-free synthesis without using expensive materials for preparing the electrocatalyst layer, the proposed electrode can be used as a good candidate for water splitting in the presence of urea.

Iron and vanadium co-doped Ni3S2 flower like nanosheets as an efficient electrocatalysts for water splitting

For the production of sustainable hydrogen energy from water electrolysis, it is now essential to create an efficient bifunctional electrocatalysts for OER and HER (oxygen and hydrogen evolution reaction). We have synthesized a bi-metallic heterogeneous electrocatalyst of iron and vanadium codoped nickel sulphide (FeV-Ni3S2) flower like nanosheets self-supported on conductive nickel foam (NF) substrate by a typical hydrothermal method. Herein, our investigation is focused on achieving an efficient electrocatalytic performance and long-term stability (> 48 h) in an alkaline environment (1 M KOH). The results of FeV-Ni3S2/NF exhibits an outstanding electrochemical performance with lower overpotentials of 149 mV for HER and 183 mV for OER at 10 mA cm−2, and a lower cell voltage of 1.56 V, respectively. The lattice distortion in Ni3S2 caused by FeV-doping, and the enrichment of sulphur active edge sites contributes to the improved electrochemical performance of FeV-Ni3S2/NF. Moreover, the interconnected flower like nanosheets increasese the conductivity, density of active sites and electrochemical surface area to facilitate the mass transport of reactants, benefiting stable water electrolysis for efficient hydrogen production. This work will provide novel insights into the design of bi-metal-doped materials for energy conversion and storage applications.

Ni2CoS4@(NiCo)Se2 bimetallic selenides with core–shell heterostructure in-situ generated on Ni2CoS4 nanorods arrays for high performance supercapacitors

In this paper, Ni2CoS4@(NiCo)Se2/NF core–shell structural nanocomposites are successfully prepared on nickel foam (NF) substrates through a convenient hydrothermal method and tube furnace calcination. Firstly, NiCo2O4/NF is acquired by a one-step simple hydrothermal method and one-step tube furnace calcination, then it is sulfidated via a one-step hydrothermal method, and finally selenized by stirring to obtain Ni2CoS4@(NiCo)Se2/NF. The results show that in the three-electrode test, the specific capacitance of the Ni2CoS4@(NiCo)Se2 electrode is able to reach 6054 mF·cm−2 at a current density of 10 mA·cm−2. The excellent performance of Ni2CoS4@(NiCo)Se2/NF nanocomposites is supposed to give rise to the bimetallic synergistic effect, as well as the unique core–shell structure of its surface-loaded nanosheets. In addition, all-solid-state asymmetric supercapacitors (ASCs) are composed of activated carbon (AC) as the anode and Ni2CoS4@(NiCo)Se2/NF as the cathode. The prepared Ni2CoS4@(NiCo)Se2/NF//AC ASC devices reach an energy density of 53 Wh kg−1 at a power density of 480 W kg−1. Simultaneously, Ni2CoS4@(NiCo)Se2/NF//AC ASC device has an excellent specific capacitance of 149.06F g−1 at a current density of 0.6 A/g and a capacitance retention rate of 84.0 % after 10,000 electrochemical cycles, which proves its good cycling stability. Impressively, two Ni2CoS4@(NiCo)Se2/NF//AC ASC devices connected in series can light up a 2.5 V LED lamp and continue to illuminate it for 11 min. Our results show that Ni2CoS4@(NiCo)Se2/NF nanocomposites with core–shell structures have great application potential in energy storage devices.

Phosphidation treatment of surfactant-tuned iron polyphthalocyanine grown in situ on nickel foam: An efficient bifunctional catalyst for overall water splitting

Developing robust electrocatalysts for overall water splitting is vital for industrial hydrogen production on a large scale. Herein, we obtain a bifunctional electrocatalyst NF@FePPc-s/p (where s represents surfactant and p stands for the phosphidation treatment) by phosphorization of surfactant (F127)-tuned iron polyphthalocyanine (FePPc) grown in situ on the nickel foam (NF) substrate. The as-obtained NF@FePPc-s/p exhibits the golden needle mushroom-like morphology, which is conducive to fully exposing the active sites and boosting the electron-transfer kinetics at the reaction interface. The physicochemical characterization and electrochemical measurements demonstrate that the active Fe2P and Ni2P phases formed during the phosphidation treatment are intrinsically active catalytic sites for hydrogen evolution reaction (HER), and the FeOOH formed from phase transformation of Fe2P during the oxygen evolution reaction (OER) process contributes a lot to enhancement of the OER activity. Furthermore, the electronic interaction between Fe and Ni further improves the electrocatalytic performances for both reactions. The optimized NF@FePPc-s/p catalyst exhibits remarkable OER (293 mV@100 mA cm−2) and HER (190 mV@100 mA cm−2) activities in 1.0 M KOH electrolyte. The water electrolyzer assembled with the NF@FePPc-s/p as the cathode and anode electrodes, respectively, only requires a low cell voltage of 1.743 V to obtain the current density of 100 mA cm−2 for overall water splitting, outperforming the precious NF@RuO2–Pt/C based electrolyzer (1.852 V).

CuO/Co3O4 materials grown directly on nickel foam for high-performance supercapacitor electrode

Electrochemical deposition and successive ionic layer adsorption and reaction (SILAR) are two widely used techniques for preparing semiconductor materials. However, there is limited research on combining the two methods to prepare CuO and Co3O4 composites for supercapacitor applications. In this study, CuO/Co3O4 semiconductor composites with spherical (S–CuO/Co3O4) and wheat spike (W–CuO/Co3O4) morphologies were prepared on nickel foam substrate using a combination of electrochemical deposition and successive ion-layer adsorption. The composites were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy to confirm their composition and morphology. The electrochemical properties of CuO/Co3O4 materials were investigated using CV, GCD, and EIS. The results show that the load cycle has a significant impact on the performance of CuO/Co3O4, with a load period of 10 cycles exhibiting the best electrochemical performance. A comparison also reveals that the performance of the W–CuO/Co3O4 electrode is better than that of the S–CuO/Co3O4 electrode. In particular, at 1 mA/cm2 current density, the specific capacity of the W–CuO/Co3O4-10 electrode is 86.0 mAh/g, which is larger compared to S–CuO/Co3O4-10 electrode (55.8 mAh/g). After 5000 cycles of galvanostatic charge/discharge, the capacitance retention rate of the W–CuO/Co3O4-10 electrode remains 76.9 %. In addition, two water-system symmetrical supercapacitors connected in series can light up the LED for 8 min and still maintain a certain brightness. Modifying the morphology of composites has a significant impact on improving the capacitive properties of composites. This study demonstrates that the prepared CuO/Co3O4 composite material has good application potential as electrode material for supercapacitors.

Ultra-fast electrodeposition of dynamic hydrogen bubble template nickel sulfide on a porous copper layer as an electrocatalyst toward hydrogen evolution reaction

Finding cost-effective electrocatalysts that can match the performance of noble metals like platinum is crucial for renewable hydrogen energy generation. In this study, the electrocatalytic properties of a nickel sulfide compound deposited on a porous copper network that is formed on a nickel foam substrate are investigated. To achieve this goal, the dynamic hydrogen bubble template method was employed. Copper and nickel sulfide electrodeposited in 5 s at 6 A cm−2. The presence of the copper layer resulted in a potential requirement of 98 mV, to achieve current densities of 10 mA cm−2, compared to 120 mV, when the porous copper substrate was not present. The ECSA was found to be significantly increased by the presence of the copper layer, as determined by examining the CV test and calculating the electrochemically active surface area. Ni3S2@Cu@NF is an excellent choice for electrocatalyst when it comes to HER in alkaline media.

One-step electrodeposition of NiS heterostructures on nickel foam electrodes for hydrogen evolution reaction: on the impact of thiourea content

Herein, we report on the one-step growth of nickel sulfide (NiS) heterostructures on nickel foam (NF) substrate via a facile electrodeposition method, employing Ni(NO3)2.6H2O and CH4N2S as Ni and S precursors, respectively. For the first time, a systematic study was carried out on the impact of the Ni/S molar ratio on the electrochemical performance of as-prepared electrodes for water splitting. The optimum performance was obtained for a Ni:S ratio equal to 2:1, whereas lower or higher ratios resulted in much inferior performance. The NiS@NF electrode with a Ni:S ratio of 2:1 exhibited the lowest overpotentials |η10| = 136 mV, |η100| = 209 mV, extremely low Tafel slope (60 mV dec-1), and very high double layer capacitance value (2.78 mF cm-2). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and X-ray photoelectron spectroscopy (XPS) revealed the formation of coral-like nanoarchitecture, resulting in enhanced HER activity.

Interfacial electronic structure modulation enables PdAg/NiOx an advanced oxygen evolution electrocatalyst

Hydrogen production by electrolysis of water is one of the solutions to energy problems and environmental pollution. The design of efficient oxygen evolution electrocatalyst remains a challenging. One way to improve catalytic performance is to change the morphology and structure of the catalyst. Herein, a two-dimensional (2D) flake nano-flower heterostructured catalyst was designed on nickel foam (NF) substrate by simple hydrothermal and thermal annealing reactions. Benefiting from the porous nanosheet structure and synergistic effect between PdAg and NiOx, which facilitates electrolyte transport, the PdAg/NiOx nanosheets deliver a low overpotential (253 mV @ 10 mA cm−2) for oxygen evolution reaction (OER) and has excellent stability. In addition, the addition of PdAg alloy regulates the electronic structure of the active component Ni, which also makes for further improving the electrocatalytic OER performance. This work not only offers a promising strategy of in situ anchoring PdAg alloy on NiOx nanosheet but also provide a new way for the application of alloy heterogeneous interfaces to high performance OER catalysts.

Cobalt doped NiFe2O4 on 3D nickel foam substrate for electrochemical detection of uric acid

The development of a facile and cost-effective uric acid (UA) sensor is of significant importance in the diagnosis of hyperuricemia so that further complications in our body can be avoided due to the early detection. Herein, pristine NiFe2O4 and cobalt-doped NiFe2O4 CoxNi1-xFe2O4 (x = 0.01, 0.03, 0.05) were synthesised and coated on nickel foam (NF) to fabricate a new electrode and was investigated for non-enzymatic UA detection in Phosphate Buffer Saline (PBS, pH = 7.4). The Co0.01Ni0.99Fe2O4 showed better electrochemical activity compared to the pristine NiFe2O4 due to its higher electrochemically-active surface area. The linear response for the UA sensing using amperometric studies was observed in the range of 4 μM to 5.28 mM with a short response time with a detection limit of (LoD) 6.38 μM and a sensitivity of 2.898 mA mM−1 cm−2. The selectivity of the developed biosensor was studied by adding interferents and it showed no prominent interferents as validated using Differential Pulse Voltammetry (DPV). The stability, repeatability and reproducibility of the electrode was also studied. The fabricated Co0.01Ni0.99Fe2O4@NF biosensor was further used to detect UA in spot-urine samples showing recovery between 78 to 92 % and therefore it has promising applications in clinics where highly sensitive and selective biosensors are required.

Clever fusion of structure and function: A coupled sulfurization-driven OER performance study based on ZIF-67 nanoparticles and NiMoO4 nanorods

Hydrogen fuel cells (HFCs) and water electrolysis are emerging clean energy technologies that can alleviate the problems of environmental pollution and energy shortage. Oxygen Extraction Reaction (OER) is a slow four-electron transfer process with a high energy barrier, and often regarded as the bottleneck of a series of clean energy technologies. In this paper, NiMoO4 nanorods (denoted as NMO) were in situ grown on nickel foam substrate, and then ZIF-67 nanoparticles were assembled onto NiMoO4 nanorods (denoted as NMO@ZIF-67). Finally, the surface layers of NiMoO4 nanorods and ZIF-67 nanoparticles were vulcanized by hydrothermal treatment for 6 h to obtain the catalyst NiMoO4 @NiMoCo-S-6 (denoted as NMO@NMC-S-6). In 1 M KOH aqueous solution, NMO@NMC-S-6 exhibited excellent electrochemical performance, only 176 mV and 243 mV overpotentials were required at current densities of 10 and 100 mA cm-2, respectively, and Tafel slope of NMO@NMC-S-6 is 24.81 mV dec-1. In addition, benefitting from the combined structure of nanorods and nanoparticles effectively prevented nanoparticles aggregation and enhanced its own structure and transport channel stability, NMO@NMC-S-6 showed remarkable stability in 20 h electrochemical test. This work brings a reference orientation for constructing cost-efficient alkaline OER catalyst through structure combination strategy.

HEA-NiFeCuCoCe/NF through ultra-fast electrochemical self-reconstruction with high catalytic activity and corrosion resistance for seawater electrolysis

The development of an electrocatalyst with excellent corrosion resistance and catalytic performance in seawater electrolysis is of great significance for advancing and utilizing sustainable hydrogen energy in the future. Additionally, the exploration of actual active sites to enhance the performance of OER (oxygen evolution reaction) is highly valuable in improving the overall efficiency of water electrolysis. To achieve these objectives, we synthesized a Ni-Fe-Cu-Co-Ce high entropy alloy (HEA-NCFCC) on a nickel foam (NF) substrate through electrodeposition. Subsequently, by employing an effective electrochemical self-reconstruction method, we successfully introduced M−OOH on the surface of the HEA-NCFCC/NF, resulting in a catalyst that exhibits both high OER activity and exceptional corrosion resistance (HEA-NCFCC/NF@EA). The catalyst's exceptional OER performance was clearly demonstrated by the experimental results, as evidenced by the achieved overpotentials of 219 mV, 220 mV, and 236 mV at current densities of 10 mA·cm−2 in alkaline solution, alkaline simulated seawater, and alkaline seawater, respectively. Furthermore, the HEA-NCFCC/NF@EA exhibited remarkable stability during continuous OER operation in alkaline simulated seawater and alkaline seawater, with a minimum operating time of 100 h. The outstanding corrosion resistance and catalytic performance of the HEA-NCFCC/NF@EA resulted from the distinctive synergistic effect intrinsic to the high entropy alloy itself and the incorporation of a stable lattice oxygen mechanism through electrochemical self-restructuring. This ensured that the catalyst remained highly resistant to significant erosion and reconstruction caused by chloride ions during continuous seawater electrolysis.

Concurrent electrocatalytic hydrogen evolution and polyethylene terephthalate plastics reforming by self-supported amorphous cobalt iron phosphide electrode

The electrocatalytic hydrogen evolution reaction (HER) coupled with oxidative transformation of plastics into commodity chemical is a promising tactic to relieve the energy shortage and white pollution problems via sustainable and profitable manner, which necessitates highly active bifunctional catalytic electrode and meticulous construction of electrolysis system. Herein, a self-supported amorphous cobalt iron phosphide onto nickel foam (NF) substrate, labeled as CoFe-P/NF, was prepared by electrodeposition, which served as bifunctional catalytic electrode for alkali hydrogen evolution reaction (HER) and selective electrooxidation of polyethylene terephthalate (PET) plastic hydrolysate toward formate. Benefiting from the abundant catalytic sites within amorphous structure, the interelement synergy and sufficient exposure of catalyst to electrolyte, the self-supported CoFe-P/NF electrode displayed low overpotential (η100 of 168 mV at current density of J = 100 mA cm−2), decent stability for HER and fine tolerance to PET monomers. The CoFe-P/NF electrode could also catalyze selective electrooxidation of ethylene glycol (EG) component in PET hydrolysate to formate with high productivity (0.1 mmol cm-2h−1) and faradaic efficiency (FE, 90 %) at 1.5 V. The PET hydrolysate electrolysis system based on CoFe-P/NF enabled coproduction of H2 and value added formate at lower voltage (1.52 V at J = 20 mA cm−2) and energy consumption (84 % at J = 200 mA cm−2) relative to water electrolysis. This work showcases the coproduction of H2 fuel and formate by electrolysis of PET hydrolysate via rational design of bifunctional catalytic electrode. We believe such type of versatile catalytic electrodes can find application scenarios in electrosynthesis of more commodity chemicals and energy devices beyond the case herein.

Construction active sites in nickel sulfide by dual-doping vanadium/cobalt for highly effective oxygen evolution reaction

Rational design and exploration of oxygen evolution reaction (OER) electrocatalysts with exceptional performance are crucial for the advancement of the hydrogen energy economy. In this study, vanadium/cobalt (V/Co) dual-doped nickel sulfide (Ni3S2) nanowires were synthesized on a nickel foam (NF) substrate to overcome the sluggish kinetics typically associated with OER. The resulting catalyst exhibited outstanding electrocatalytic activity towards OER in a 1.0 M KOH electrolyte, with a minimal overpotential of 155 and 263 mV, the current densities of 10 and 100 mA cm−2 can be achieved effortlessly. Importantly, this catalyst demonstrated remarkable stability over extended periods, maintaining its performance for 25 h under constant current density, 55 h under continuously varying current density, and even after undergoing 2000 cycles of cyclic voltammetry (CV), which had surpassed those of most non-noble metal electrocatalysts. The X-ray photoelectron spectroscopy and density functional theory analyses confirmed that the co-doping of Co and V redistributed the electron of Ni, leading to improvements in the d-band center, structural characteristics, and free energy landscapes of adsorbed intermediates. This work presents a novel strategy, based on the connection between electronic structure and catalytic properties, in the design of double-doped catalysts for efficient OER.