Search Results (44)

Nickel phosphide catalysts (Ni₂P) were prepared using mesoporous molecular sieves as supports during isobaric co-impregnation. Ni₂P catalysts with different loading values were characterized, showing that the active phase on the surface of the catalysts was mainly Ni₂P and the catalysts still retained the mesoporous structural characteristics of the supports. The catalysts were evaluated using a 10 mL fixed-bed hydrogenation unit. The results showed that the nickel phosphide catalysts had a higher hydrogenation capacity than the sulfide catalysts and were able to preferentially hydrogenate and saturate most of the quinolines to decahydroquinolines, reduce the conversion of 1,2,3,4-tetrahydroquinoline to o-propylaniline, and reduce the inhibition of reactivity due to competitive adsorption. The effect of the catalyst on the path selectivity of quinoline hydrogenation was investigated, and the products of quinoline hydrogenation and denitrogenation consisted mainly of propylbenzene and propylcyclohexane, with propylcyclohexane accounting for 91.7% of the product and propylbenzene for 4.8%, under the conditions of nickel phosphide catalysts. Furthermore, the 25 wt% Ni₂P/SBA-15 catalyst exhibited no significant loss of catalytic activity during a 72 h stability evaluation conducted at 360 °C. Full article

Developing efficient bifunctional electrocatalysts with excellent stability at high current densities for overall water splitting is a challenging yet essential objective. However, transition metal phosphides encounter issues such as poor dispersibility, low specific surface area, and limited electronic conductivity, which hinder the achievement of satisfactory performance. Therefore, this study presents the highly efficient bifunctional electrocatalyst of CeO₂-modified NiFe phosphide on nickel foam (CeO₂/Ni₂P/Fe₂P/NF). Ni₂P/Fe₂P coupled with CeO₂ was deposited on nickel foam through hydrothermal synthesis and sequential calcination processes. The electrocatalytic performance of the catalyst was evaluated in an alkaline solution, and it exhibited an HER overpotential of 87 mV at the current density of 10 mA cm⁻² and an OER overpotential of 228 mV at the current density of 150 mA cm⁻². Furthermore, the catalyst demonstrated good stability, with a retention rate of 91.2% for the HER and 97.3% for the OER after 160 h of stability tests. The excellent electrochemical performance can be attributed to the following factors: (1) The interface between Ni₂P/Fe₂P and CeO₂ facilitates electron transfer and reactant adsorption, thereby improving catalytic activity. (2) The three-dimensional porous structure of nickel foam provides an ideal substrate for the uniform distribution of Ni₂P, Fe₂P, and CeO₂ nanoparticles, while its high conductivity facilitates electron transport. (3) The incorporation of larger Ce³⁺ ions in place of smaller Fe³⁺ ions leads to lattice distortion and an increase in defects within the NiFe-layered double hydroxide structure, significantly enhancing its catalytic performance. This research finding offers an effective strategy for the design and synthesis of low-cost, high-potential catalysts for water electrolysis. Full article

Nickel phosphides (Ni_xP_y) are recognized as promising alternatives to noble-metal catalysts for the oxygen evolution reaction (OER). NiP, consisting of the equal stoichiometric ratio of Ni and P, could help quantify the catalytic effect of P and Ni. In this work, density functional theory (DFT) is employed to investigate the OER mechanism on NiP surfaces. We found that P atoms help stabilize O* at the adsorption sites. The rich electron donation from the Ni atom can alter the local charge distribution and enhance the interaction between O* and P atoms. Both oxygen intermediate adsorption energy and OER overpotential exhibit linear correlations with the charge of adsorption sites. Electron loss at the site induces the overall system to exhibit Lewis acidic characteristics, facilitating the OER and leading to a substantial overpotential reduction of up to 0.61 V compared to Lewis basic structures. Leveraging electronic structure theory and Lewis acid–base theory, we offer a new insight into the OER mechanism on the NiP surface, demonstrating that the catalytic activity of bulk metallic surface materials like NiP can be optimized by tailoring the local surface chemical environment. Full article

Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni₂P and Ni₁₂P₅), synthesized using dopamine (PDA) and ammonium phosphate as eco-friendly precursors. The phase formation of nickel phosphides was found to be highly dependent on the P/PDA ratio (0.15, 0.3, 0.6, and 0.9), allowing for the selective synthesis of Ni₂P or Ni₁₂P₅. Operando Raman spectroscopy revealed that both phases undergo surface transformation into nickel (oxy)hydroxide species under OER conditions, yet Ni₂P-based catalysts demonstrated superior activity and long-term stability. This enhancement is attributed to efficient electron transfer at the dynamic Ni₂P/NiOOH interface. Additionally, hollow nanostructures formed at intermediate P/PDA ratios (≤0.3) via the Kirkendall effect and Ostwald ripening contributed to an increased specific surface area and micropore volume, further improving the catalytic performance. Electrochemical impedance spectroscopy confirmed reduced interfacial resistance and enhanced charge transport. These findings offer new insights into the rational design of high-performance electrocatalysts and propose a green, tunable synthesis approach for advanced energy conversion applications. Full article

Transition metal phosphides (TMPs) show great potential as catalysts for the hydrogen evolution reaction (HER). FeP stands out as an efficient and cost-effective non-noble metal-based HER catalyst. However, FeP tends to aggregate and suffer from instability during the reaction. To tackle these challenges, we developed an efficient and straightforward approach to load metal-organic framework-derived N/P co-doped carbon-encapsulated FeP nanoparticles onto a nickel foam substrate (FeP@NPC/NF-450). This catalyst exhibits exceptional HER activity in 0.5 M H₂SO₄ and 1.0 M KOH solutions, with overpotentials of 68.3 mV and 106.1 mV at a current density of 10 mA cm⁻², respectively. Furthermore, it demonstrates excellent stability with negligible decay over 48 h in both acidic and alkaline solutions. The outstanding hydrogen evolution catalytic performance of FeP@NPC/NF-450 is mainly due to the N, P co-doped carbon matrix, which safeguards the FeP nanoparticles from aggregation and surface oxidation. Consequently, this enhances the availability of active sites during the hydrogen evolution reaction (HER), leading to improved stability. Moreover, introducing nickel foam offers a larger specific surface area and enhances charge transfer rates. This study provides a reference method for preparing stable and highly active electrocatalysts for hydrogen evolution. Full article

Tuning the chemical and structural environment of Ru-based nanomaterials is a major challenge for achieving active and stable hydrogen evolution reaction (HER) electrocatalysis. Here, we anchored ultrafine Ru nanoparticles (with a size of ~4.2 nm) on a hierarchical Ni₂P array (Ru/Ni₂P) to enable highly efficient HER. The Ni₂P promoter weakened the adsorption of proton on Ru sites by accepting electrons from Ru nanoparticles. Moreover, the hierarchical Ni₂P endowed Ru catalysts with a large surface area and stable open structure. Consequently, the as-fabricated Ru/Ni₂P electrode displayed a low overpotential of 57 and 164 mV at the HER current densities of 10 and 50 mA cm⁻², respectively, comparable to the state-of-the-art Pt catalysts. Moreover, the Ru/Ni₂P electrode can operate stably for 96 h at 50 mA cm⁻² without performance degradation. After pairing with a commercial RuO₂ anode, the Ru/Ni₂P anode catalyzed overall water splitting at 1.73 V with a current density of 10 mA cm⁻², which was 0.16 V lower than its commercial Ni counterpart. In situ Raman studies further revealed the optimized proton adsorption at the Ru-active sites on Ni₂P promoter, thus enhancing the electrocatalytic HER performance. Full article

The significance and challenges of hydrotreatment processes for vegetable oils have recently become apparent, encompassing various reactions like decarbonylation, decarboxylation, and hydrogenation. Heterogeneous noble or transition metal catalysts play a crucial role in these reactions, offering high selectivity in removing oxygen and yielding desired hydrocarbons. Notably, both sulphided and non-sulphided catalysts exhibit effectiveness, with the latter gaining attention due to health and toxicity concerns associated with sulphiding agents. Nickel-based catalysts, such as NiP and NiC, demonstrate specific properties and tendencies in deoxygenation reactions, while palladium supported on activated carbon catalysts shows superior activity in hydrodeoxygenation. Comparisons between the performances of different catalysts in various hydrotreatment processes underscore the need for tailored approaches. Transition metal phosphides (TMP) emerge as promising catalysts due to their cost-effectiveness and environmental friendliness. Ultimately, there is an ongoing pursuit of efficient catalysts and the importance of further advancements in catalysis for the future of vegetable oil hydrotreatment. Full article

The application of electrochemical hydrogen evolution reaction (HER) for renewable energy conversion contributes to the ultimate goal of a zero-carbon emission society. Metal phosphides have been considered as promising HER catalysts in the alkaline environment, which, unfortunately, is still limited owing to the weak adsorption of H* and easy dissolution during operation. Herein, a bimetallic NiCoP-2/NF phosphide is constructed on nickel foam (NF), requiring rather low overpotentials of 150 mV and 169 mV to meet the current densities of 500 and 1000 mA cm⁻², respectively, and able to operate stably for 100 h without detectable activity decay. The excellent HER performance is obtained thanks to the synergetic catalytic effect between Ni and Co, among which Ni is introduced to enhance the intrinsic activity and Co increases the electrochemically active area. Meanwhile, the protection of the externally generated amorphous phosphorus oxide layer improves the stability of NiCoP/NF. An electrolyser using NiCoP-2/NF as both cathode and anode catalysts in an alkaline solution can produce hydrogen with low electric consumption (overpotential of 270 mV at 500 mA cm⁻²). Full article

Hydrogen, one of the most promising forms of new energy sources, due to its high energy density, low emissions, and potential to decarbonize various sectors, has attracted significant research attention. It is known that electrocatalytic hydrogen production is one of the most widely investigated research directions due to its high efficiency in the conversion of electricity to H₂ gas. However, given the limited reserves and high cost of precious metals, the search for non-precious metal-based catalysts has been widely explored, for example, transition metal phosphides, oxides, and sulfides. Despite this interest, a detailed survey unveils that the surface and internal structures of the alternative catalysts, including their surface reconstruction, composition, and electronic structure, are poorly studied. As a result, a disconnection in the structure–property relationship severely hinders the rational design of efficient and reliable non-precious metal-based catalysts. In this review, by focusing on Ni₅P₄, a bifunctional catalyst for water splitting, we systematically summarize the material motifs pertaining to the different synthetic methods, surface characteristics, and hydrolysis properties. It is believed that a cascaded correlation may provide insights toward understanding the fundamental catalytic mechanism and design of robust alternative catalysts for hydrogen production. Full article

Graphitic carbon nitride is considered as an ideal semiconductor material for photocatalytic hydrogen evolution due to its suitable energy band structure, durability and environmental friendliness. To further improve the catalytic performance of g-C₃N₄, nickel phosphide-loaded one-dimensional tubular carbon nitride (Ni₂P/TCN) was prepared by thermal polymerization and photo deposition. The beneficial effect of the one-dimensional tubular structure on hydrogen generation was mainly attributed to its larger specific surface area (increased light absorption) as well as the linear movement of the carriers, which reduced their diffusion distance to the surface and facilitated the separation of photogenerated carriers. The loading of Ni₂P co-catalyst improved the visible light utilization efficiency and enabled the migration of photogenerated electrons towards Ni₂P, which ultimately reacted with the enhanced adsorbed H⁺ on the Ni₂P surface to facilitate the photocatalytic hydrogen evolution process. This study provides new clues for the further development of efficient, environmentally friendly and low-cost g-C₃N₄ catalysts. Full article

Electrolytic water splitting is a promising path for the production of clean hydrogen when combined with green electric power, such as photovoltaic and wind power; however, the high current water electrolysis is mainly dependent on the utilization of Pt, Ru, and other expensive materials, while the transition metal-based catalysts still need improvement in electrocatalytic activity and stability. Here, we present the preparation of economic and scalable electrode materials, Nickel-Iron phosphide/Nickel foam (NiFeP/NF), with a hierarchical porous structure for overall water splitting as both the anode and cathode. An overall potential of 1.85 V for the current density of 100 mA cm⁻², and a long lifetime of 700 h, were achieved by using NiFeP/NF as both the anode and cathode. The nanostructures of the composite phosphides were investigated and the spent electrode after long-term electrolysis was characterized to investigate the long-term failure mechanism of the phosphides. Surface shedding and reconstruction theories were proposed for the failure of the NiFeP/NF cathode and anode in long-term electrolysis, respectively. Furthermore, TiO₂ coating was proved to be an efficient strategy to elongate the lifetime of the phosphide electrodes, which shows a slow current decline rate of 0.49 mA·cm⁻² h⁻¹. Full article

Ternary transition metal phosphides (TTMPs) with two-dimensional heterointerface and adjustable electronic structures have been widely studied in hydrogen evolution reactions (HER). However, single-phase TMPs often have inappropriate H* adsorption energy and electronic transfer efficiency in HER. Herein, we utilized the heterogeneity in the crystal structure to design an efficient and stable catalyst from the NiCoP nanowire@NiCoP nanosheet on nickel foam (NW-NiCoP@NS-NiCoP/NF) for HER. Layered double hydroxides (LDHs) with a heterogeneous matrix on crystal surfaces were grown under different reaction conditions, and non-metallic P was introduced by anion exchange to adjust the electronic structure of the transition metals. The hierarchical structure of homologous NiCoP/NF from the LDH allows for a larger surface area, which results in more active sites and improved gas diffusion. The optimized NW-NiCoP@NS-NiCoP/NF electrode exhibits excellent HER activity, with an overpotential of 144 mV, a Tafel slope of 84.2 mV dec⁻¹ at a current density of 100 mA cm⁻² and remarkable stability for more than 500 h in 1.0 M KOH electrolyte. This work provides ideas for elucidating the rational design of structural heterogeneity as an efficient electrocatalyst and the in situ construction of hierarchical structures. Full article

This study investigates the influence of the phosphorus-to-nickel (P:Ni) ratio on methanol steam reforming (MSR) over nickel phosphide catalysts using density functional theory (DFT) calculations. The catalytic behavior of Ni(111) and Ni₁₂P₅(001) surfaces was explored and contrasted to our previous results from research on Ni₂P(001). The DFT-predicted barriers reveal that Ni(111) predominantly favors the methanol decomposition route, where methanol is converted into carbon monoxide through a stepwise pathway involving CH₃OH* → CH₃O* → CH₂O* → CHO* → CO*. On the other hand, Ni₁₂P₅ with a P:Ni atomic ratio of 0.42 (5:12) exhibits a substantial increase in selectivity towards methanol steam reforming (MSR) relative to methanol decomposition. In this pathway, formaldehyde is transformed into CO₂ through a sequence of reactions involving CH₂O*→ H₂COOH* → HCOOH* → HCOO* → CO₂. The introduction of phosphorus into the catalyst alters the surface morphology and electronic structure, favoring the MSR pathway. However, with a further increase in the P:Ni atomic ratio to 0.5 (1:2) on Ni₂P catalysts, the selectivity towards MSR decreases, resulting in a more balanced competition between methanol decomposition and MSR. These results highlight the significance of tuning the P:Ni atomic ratio in designing efficient catalysts for the selective production of CO₂ through the MSR route, offering valuable insights into optimizing nickel phosphide catalysts for desired chemical transformations. Full article

The annual production of plastic waste is a serious ecological problem as it causes substantial pollution of the environment. Polyethylene terephthalate, a material usually found in disposable plastic bottles, is one of the most popular material used for packaging in the world. In this paper, it is proposed to recycle polyethylene terephthalate waste bottles into benzene-toluene-xylene fraction using a heterogeneous nickel phosphide catalyst formed in situ during the polyethylene terephthalate recycling process. The catalyst obtained was characterized using powder X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. The catalyst was shown to contain a Ni₂P phase. Its activity was studied in a temperature range of 250–400 °C and a H₂ pressure range of 5–9 MPa. The highest selectivity for benzene-toluene-xylene fraction was 93% at quantitative conversion. Full article

The aim of this study was to synthesize chemically activated carbons from different agricultural residues, i.e., pistachio shell (PS), bitter orange peel (OP), and saffron petal (SP), and subsequently to use them as supports for loading a Ni catalyst. Supercritical water gasification of bio-oil was applied to investigate the catalytic performance of the resulting catalysts. The physicochemical properties of the activated carbon (ACs) and the catalysts (Ni/ACs) were characterized with BET, XRD, XPS, TEM, and TPD. The adsorption results showed that the ACs developed considerable pore structures, containing both micro- and mesopores, which was validated by the well-distributed active phases on the supports in the TEM images. Furthermore, it was found that the BET of AC(PS) was 1410 m²/g, which was higher than that of AC(OP) (1085 m²/g) and AC(SP) (900 m²/g). The results obtained from XRD mainly indicated the presence of the nickel phosphides phases, which was confirmed with the XPS and TPD analyses. The catalytic tests showed that by raising the process temperature, the total amount of gas and hydrogen increased. Furthermore, Ni/AC(PS) showed a superior catalytic activity. The highest total gas amount (i.e., 7.87 mmol/g bio-oil), together with 37.2 vol.% H₂, was achieved using Ni/AC(PS) with a 1:10:100 catalyst:bio-oil weight ratio and a mass ratio of 1:10 (bio-oil/water) at T = 550 °C. Full article