Search Results (8)

A stable and efficient porous nickel phosphate (p-NiPO/Ti) electrocatalyst on titanium sheets was developed via electrochemical deposition and low-temperature phosphatization. For obtaining the optimal performance of the p-NiPO/Ti electrocatalyst, the optimized experimental parameters of deposition and phosphatization were determined by parallel experiments. After the preparation, XPS and XRD were used to validate the chemical and amorphous structure, with SEM and TEM simultaneously validating a distinct nanosheet/nanocluster crosslinked microstructure. In particular, with phosphatization conditions maintained at 300 °C for 10 min, the p-NiPO/Ti produced demonstrated excellent charge transfer and catalytic characteristics in 1.0 M KOH. The electrocatalytic results revealed that the optimal p-NiPO/Ti with excellent catalytic performance and excellent stability (~24 h) needs lower HER overpotentials (128 mV at 10 mA cm⁻² and 242 mV at 100 mA cm⁻²) as inputs. This research provides a promising strategy with which to use transition metal materials as catalysts in alkaline electrocatalytic hydrogen production. Full article

Alkaline aqueous zinc-ion batteries possess a wider potential window than those in mildly acidic systems; they can achieve high energy density and are expected to become the next generation of energy storage devices. In this paper, a hollow porous P-NiCo₂O₄@Co₃O₄ nanoarray is obtained by ion etching and the calcination and phosphating of ZiF-67, which is directly grown on foam nickel substrate, as a precursor. It exhibits excellent performance as a cathode material for alkaline aqueous zinc-ion batteries. A high discharge specific capacity of 225.3 mAh g⁻¹ is obtained at 1 A g⁻¹ current density, and it remains 81.9% when the current density is increased to 10 A g⁻¹. After one thousand cycles of charging and discharging at 3 A g⁻¹ current density, the capacity retention rate is 88.8%. Even at an excellent power density of 25.5 kW kg⁻¹, it maintains a high energy density of 304.5 Wh kg⁻¹. It is a vital, promising high-power energy storage device for large-scale applications. Full article

The construction of multi-level heterostructure materials is an effective way to further the catalytic activity of catalysts. Here, we assembled self-supporting MoS₂@Co precursor nanoarrays on the support of nickel foam by coupling the hydrothermal method and electrostatic adsorption method, followed by a low-temperature phosphating strategy to obtain Mo₄P₃@CoP/NF electrode materials. The construction of the Mo₄P₃@CoP heterojunction can lead to electron transfer from the Mo₄P₃ phase to the CoP phase at the phase interface region, thereby optimizing the charge structure of the active sites. Not only that, the introduction of Mo₄P₃ will make water molecules preferentially adsorb on its surface, which will help to reduce the water molecule decomposition energy barrier of the Mo₄P₃@CoP heterojunction. Subsequently, H* overflowed to the surface of CoP to generate H₂ molecules, which finally showed a lower water molecule decomposition energy barrier and better intermediate adsorption energy. Based on this, the material shows excellent HER/OER dual-functional catalytic performance under alkaline conditions. It only needs 72 mV and 238 mV to reach 10 mA/cm² for HER and OER, respectively. Meanwhile, in a two-electrode system, only 1.54 V is needed to reach 10 mA/cm², which is even better than the commercial RuO₂/NF||Pt/C/NF electrode pair. In addition, the unique self-supporting structure design ensures unimpeded electron transmission between the loaded nanoarray and the conductive substrate. The loose porous surface design is not only conducive to the full exposure of more catalytic sites on the surface but also facilitates the smooth escape of gas after production so as to improve the utilization rate of active sites. This work has important guiding significance for the design and development of high-performance bifunctional electrolytic water catalysts. Full article

Phosphoric acid-based porous geopolymers were prepared by two different foaming agents (H₂O₂ and Al powder) with phosphoric acid as the activator. High-magnesium nickel slag (HMNS) and fly ash (FA) were the precursor combination. The effects of foaming agent types and contents on the properties of HMNS-FA-phosphate-based porous geopolymers were investigated in terms of dry density, pore structure, compressive strength, thermal conductivity, and water absorption. The phase was analyzed by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). It was found that both foaming agents could successfully prepare porous geopolymers, and the compressive strength and dry density of porous geopolymers gradually decreased and the low-thermal conductivity and water absorption gradually increased with the increase in foaming agent content. The foaming agents formed porous structures inside porous geopolymers but did not affect the phases of geopolymerization reactions. This study demonstrates that both foaming agents can be used to prepare HMNS-FA-phosphate-based porous geopolymers for the application of phosphate-activated geopolymers in the direction of refractory materials. Full article

The development of non-noble metal catalysts for water electrolysis to product hydrogen meets the current strategic need for carbon peaking and carbon neutrality. However, complex preparation methods, low catalytic activity and high energy consumption still limit the application of these materials. Herein, in this work we prepared a three-level structured electrocatalyst of CoP@ZIF-8 growing on modified porous nickel foam (pNF) via the natural growing and phosphating process. In contrast to the common NF, the modified NF constructs a large number of micron-sized pores carrying the nanoscaled catalytic CoP@ZIF-8 on the millimeter-sized skeleton of bare NF, which significantly increases the specific surface area and catalyst load of the material. Thanks to the unique spatial three-level porous structure, electrochemical tests showed a low overpotential of 77 mV at 10 mA cm⁻² for HER, and 226 mV at 10 mA cm⁻² and 331 mV at 50 mA cm⁻² for OER. The result obtained from testing the electrode’s overall water splitting performance is also satisfactory, needing only 1.57 V at 10 mA cm⁻². Additionally, this electrocatalyst showed great stability for more than 55 h when a 10 mA cm⁻² constant current was applied to it. Based on the above characteristics, the present work demonstrates the promising application of this material to the electrolysis of water for the production of hydrogen and oxygen. Full article

Heterostructured non-precious metal phosphides have attracted increasing attention in the development of high-performance catalysts for hydrogen evolution reaction (HER), particularly in acidic media. Herein, a catalyst composed of ternary Ni₅P₄-NiP₂-Ni₂P nanocomposites and N-doped carbon nanotubes/carbon particulates (Ni₅P₄-NiP₂-Ni₂P/NC) was prepared from a Ni-containing hybrid precursor through approaches of a successive carbonization and phosphating reaction. Benefiting from the synergistic effect from three-component nickel phosphides and the support role of porous carbon network, the Ni₅P₄-NiP₂-Ni₂P/N-doped carbon catalyst presents the promising HER performance with overpotentials of 168 and 202 mV at the current density of 10 mA cm⁻² and Tafel slopes of 69.0 and 74 mV dec⁻¹ in both acidic and alkaline solutions, respectively, which surpasses the Ni₂P/N-doped carbon counterpart. This work provides an effective strategy for the preparation and development of highly efficient HER non-precious metal electrocatalysts by creating heterostructure in acidic and alkaline media. Full article

The electro-oxidation of urea (EOU) is a remarkable but challenging sustainable technology, which largely needs a reduced electro-chemical potential, that demonstrates the ability to remove a notable harmful material from wastewater and/or transform the excretory product of humans into treasure. In this work, an Ni₂P-nanoparticle-integrated porous nickel oxide (NiO) hetero-structured nanosheet (Ni₂P@NiO/NiF) catalyst was synthesized through in situ acid etching and a gas-phase phosphating process. The as-synthesized Ni₂P@NiO/NiF catalyst sample was then used to enhance the electro-oxidation reaction of urea with a higher urea oxidation response (50 mA cm⁻² at 1.31 V vs. RHE) and low onset oxidation potential (1.31 V). The enhanced activity of the Ni₂P@NiO/NiF catalyst was mainly attributed to effective electron transport after Ni₂P nanoparticle insertion through a substantial improvement in active sites due to a larger electrochemical surface area, and a faster diffusion of ions occurred via the interactive sites at the interface of Ni₂P and NiO; thus, the structural reliability was retained, which was further evidenced by the low charge transfer resistance. Further, the Ni₂P nanoparticle insertion process into the NiO hetero-structured nanosheets effectively enabled a synergetic effect when compared to the counter of the Ni₂P/NiF and NiO/NiF catalysts. Finally, we demonstrate that the as-synthesized Ni₂P@NiO/NiF catalyst could be a promising electrode for the EOU in urea-rich wastewater and human urine samples for environmental safety management. Overall, the Ni₂P@NiO/NiF catalyst electrode combines the advantages of the Ni₂P catalyst, NiO nanosheet network, and NiF current collector for enhanced EOU performance, which is highly valuable in catalyst development for environmental safety applications. Full article

In this paper, we tested the combined use of a biochar-based material at the cathode and of Pseudomonas aeruginosa strain in a single chamber, air cathode microbial fuel cells (MFCs) fed with a mix of shredded vegetable and phosphate buffer solution (PBS) in a 30% solid/liquid ratio. As a control system, we set up and tested MFCs provided with a composite cathode made up of a nickel mesh current collector, activated carbon and a single porous poly tetra fluoro ethylene (PTFE) diffusion layer. At the end of the experiments, we compared the performance of the two systems, in the presence and absence of P. aeruginosa, in terms of electric outputs. We also explored the potential reutilization of cathodes. Unlike composite material, biochar showed a life span of up to 3 cycles of 15 days each, with a pH of the feedstock kept in a range of neutrality. In order to relate the electric performance to the amount of solid substrates used as source of carbon and energy, besides of cathode surface, we referred power density (PD) and current density (CD) to kg of biomass used. The maximum outputs obtained when using the sole microflora were, on average, respectively 0.19 Wm⁻²kg⁻¹ and 2.67 Wm⁻²kg⁻¹, with peaks of 0.32 Wm⁻²kg⁻¹ and 4.87 Wm⁻²kg⁻¹ of cathode surface and mass of treated biomass in MFCs with biochar and PTFE cathodes respectively. As to current outputs, the maximum values were 7.5 Am⁻² kg⁻¹ and 35.6 Am⁻²kg⁻¹ in MFCs with biochar-based material and a composite cathode. If compared to the utilization of the sole acidogenic/acetogenic microflora in vegetable residues, we observed an increment of the power outputs of about 16.5 folds in both systems when we added P. aeruginosa to the shredded vegetables. Even though the MFCs with PTFE-cathode achieved the highest performance in terms of PD and CD, they underwent a fouling episode after about 10 days of operation, with a dramatic decrease in pH and both PD and CD. Our results confirm the potentialities of the utilization of biochar-based materials in waste treatment and bioenergy production. Full article