Catalytic decomposition of toxic chemicals over iron group metals supported on carbon nanotubes

Catalytic Decomposition Mechanism of PH3 on 3DCuO/C and High Value Utilization of Deactivated Catalysts

With the widespread application of lithium iron phosphate batteries, the production capacity of the yellow phosphorus industry has increased sharply, and the treatment of the highly toxic by-product PH₃ is facing severe challenges. In this study, a 3D copper-based catalyst (3DCuO/C) that can efficiently decompose PH₃ at low temperatures and low oxygen concentrations is synthesized. The PH₃ capacity is up to 181.41 mg g^-1 , which is superior to that previously reported in the literature. Further studies indicated that the special 3D structure of 3DCuO/C induces oxygen vacancies on the surface of CuO, which is beneficial to the activation of O₂ , and then promotes the adsorption and dissociation of PH₃ . The doping of P after dissociation determines the formation of Cu-P, and the eventual conversion to Cu₃ P leads to the deactivation of CuO active sites. More strikingly, due to the appearance of Cu₃ P, the deactivated De-3DCuO/C (Cu₃ P/C) exhibited significant activity in the photocatalytic degradation of rhodamine B and photocatalytic oxidation of Hg⁰ (gas) and can also be a candidate as an anode material for Li batteries after modification, which will provide a more thorough and economical treatment scheme for deactivated catalysts.

Two Birds with One Stone: Copper-Based Adsorbents Used for Photocatalytic Oxidation of Hg0 (Gas) after Removal of PH3

Cu_X/TiO₂ adsorbents with CuO as the active component were prepared via a simple impregnation method for efficient purification of phosphine (PH₃) under the conditions of low temperatures (90 °C) and low oxygen concentration (1%). The PH₃ breakthrough capacity of optimal adsorbent (Cu₃₀/TiO₂) is 136.2 mg(PH₃)·g_sorbent^-1, and the excellent dephosphorization performance is mainly attributed to its abundant sur face-active oxygen and alkaline sites, large specific surface area, and strong interaction between CuO and the support TiO₂. Surprisingly, CuO is converted to Cu₃P after the dephosphorization by Cu_X/TiO₂. Since Cu₃P is a P-type semiconductor with high added value, the deactivated adsorbent (Cu₃P/TiO₂) is an efficient heterostructure photocatalyst for photocatalytic removal of Hg⁰ (gas) with the Hg⁰ removal performance of 92.64% under visible light. This study provides a feasible strategy for the efficient removal and resource conversion of PH₃ under low-temperature conditions and the alleviation of the environmental risk of secondary pollution.

Highly active Ni/Fe3O4/TiO2 nanocatalysts with tunable interfacial interactions for PH3 decomposition

The mixed-metal oxide Ni/Fe₃O₄/TiO₂ with two metal-oxide interfaces to catalyze sequential chemical reactions was first applied in the decomposition of phosphine gas for yellow phosphorus (P₄) production. The catalyst was prepared with tunable Ni-Fe₃O₄ and Ni-TiO₂ interactions via annealing and subsequent reduction. Ni/Fe₃O₄/TiO₂ exhibited significantly effective activity and good stability in the PH₃ decomposition, which were achieved by modulating the metal-support interaction. The characterizations by scanning electron microscopy(SEM), X-ray diffraction analysis(XRD), BET surface area measurement and X-ray photoelectron spectroscopy(XPS) were carried out. The enhancements of the Ni-Fe₃O₄ and Ni-TiO₂ dual interactions by annealing and reduction were verified and the mechanism of PH₃ decomposition over the modulated Ni/Fe₃O₄/TiO₂ catalyst was investigated. NiOOH as an active catalytic intermediate species is produced by the synergistic catalytical dual interfaces. The catalytic reaction pathways of PH₃ decomposition by the dual interfaces were firstly revealed. The results provide underlying insights in the way to promote the catalytic performance for synergistic catalysis in PH₃ decomposition.

Nickel phosphide polymorphs with an active (001) surface as excellent catalysts for water splitting

We report the temperature-controlled synthesis of two nickel phosphide polymorphs, Ni₂P and Ni₅P₄, by phosphorization of Ni foil or foams using phosphine gas, and their excellent catalytic activity toward hydrogen evolution reaction.

Co2P quantum dot embedded N, P dual-doped carbon self-supported electrodes with flexible and binder-free properties for efficient hydrogen evolution reactions

Transition metal phosphides (TMPs) are considered to be superb catalysts for water splitting. In this work, we introduce an efficient strategy to fabricate dicobalt phosphide (Co₂P) quantum dots embedded in N, P dual-doped carbon (Co₂P@NPC) on carbon cloth (Co₂P@NPC/CC) by in situ carbonization of cobalt ion induced phytic acid (PA) and polyaniline (PANI) macromolecule precursors. As a highly efficient self-supported electrode, it has a low onset overpotential (74 mV at 1 mA cm^-2) approaching that of the commercial Pt/C catalyst for the hydrogen evolution reaction (HER) in acidic media. Meanwhile, it also shows very low overpotentials of only 116 and 129 mV at 10 mA cm^-2 with robust stability in acidic and alkaline media, respectively.

Engineering a nanotubular mesoporous cobalt phosphide electrocatalyst by the Kirkendall effect towards highly efficient hydrogen evolution reactions

Tailoring the size and controlling the morphology of particular nano-architectures are considered as two promising strategies to improve the catalytic performance of metal nanocrystals towards hydrogen evolution reactions (HERs). Herein, mesoporous cobalt phosphide nanotubes (CoP-NTs) with a three-dimensional network structure have been obtained through a facile and efficient electrospinning technique combined with thermal stabilization and phosphorization treatments. The thermal stabilization process has been demonstrated to play a key role in the morphological tailoring of Co₃O₄ nanotubes (Co₃O₄-NTs). As a result, the CoP-NTs show one-dimensional hollow tubular architecture instead of forming a worm-like tubular CoP structure (W-CoP-NTs) or severely aggregated CoP powder (CoP-NPs) which originate from the Co₃O₄ nanotubes without thermal stabilization treatment and Co₃O₄ nanoparticles, respectively. Satisfyingly, under an optimized phosphorization degree, the CoP-NT electrode exhibits a low onset overpotential of 53 mV with a low Tafel slope of 50 mV dec^-1 during the HER process. Furthermore, the CoP-NT electrode is capable of driving a large cathodic current density of 10 mA cm^-2 at an overpotential of 152 mV, which is much lower than those of its contrast samples, i.e. CoP-NPs (211 mV) and W-CoP-NTs (230 mV). Therefore, this work provides a feasible and general strategy for constructing three-dimensionally organized mesoporous non-noble metal phosphide nanotubes as promising alternative high-performance electrocatalysts for the commercial platinum ones.

Nanoporous FeP nanorods grown on Ti plate as an enhanced binder-free hydrogen evolution cathode

A porous and interconnected nanorod-like FeP structure on titanium plate has been fabricated by a simple hydrothermal method and followed by a calcination process. The nanorod is assembled by many paralleled FeP nanowires with a porous structure. With the porous surface structure of FeP nanorods and the synergetic effect from the electronic conductive Ti support, this binder-free FeP electrode brings about a desirable electrocatalytic activity for the hydrogen evolution reaction (HER), showing a low onset overpotential of 23 mV and a small Tafel slope of 39 mV dec^-1. Meanwhile, its catalytic activity could be maintained almost unchanged for at least 12 h in an acidic solution. This work provides us an effective HER electrocatalyst which can be easily produced on a large scale and at low cost.

Phosphorus-containing polymers from THPS. IV: Synthesis and properties of phosphorus-containing polybenzoxazines as a green route for recycling toxic phosphine (PH3) tail gas

A convenient route to convert the highly toxic phosphine (PH₃) tail gas into high-performance polybenzoxazines was first described in this paper. Two aliphatic polyamines, namely tris(aminomethyl)phosphine oxide and bis(aminomethyl)phenylphosphine oxide, were synthesized from tetrakis(hydroxymethyl)phosphonium sulfate (THPS), a green derivative of PH₃ tail gas. And then two novel phosphorus-containing benzoxazine monomers, tris(3,4-dihydro-2H-1,3-benzoxazin-3-yl-methyl)phosphine oxide (TBOz) and benzylbis(3,4-dihydro-2H-1,3-benzoxazin-3-yl-methyl) phosphine oxide (BBOz) were prepared by three-steps procedure. FT-IR and DSC technologies were adopted to study the thermal-initiated polymerization behaviors of two benzoxazine monomers. Thermal properties of these crosslinked polymers were studied by TGA and DMA. The results display that the polybenzoxazines (PTBOz and PBBOz) exhibite good thermal stabilities and high glass transition temperatures. The char yield of polybanzoxazine is high as 47% and indiactes that phosphorus-containing polybenzoxazines show high fire-retardancy. The surface free energies of the PTBOz and PBBOz are 37.1 and 40.4mJm^-2 by Owens two-liquid method. The dielectric properties of the PTBOz and PBBOz remaine near constant in the experimental frequency range.

High Performance Graphene/Ni2 P Hybrid Anodes for Lithium and Sodium Storage through 3D Yolk-Shell-Like Nanostructural Design

A 3D yolk-shell-like electrode material composed of a porous interconnected graphene network and embedded Ni₂ P nanoparticles is designed and fabricated by an assembly and self-template strategy. This novel nanoarchitecture integrates the advantages of nanostructure and microstructure, and provides highly efficient and stable electrochemical circuits involving the active nanoparticles, leading to excellent electrochemical performance in terms of reversibility, rate capability, and cycle stability.

Metal Doping Effect of the M-Co2P/Nitrogen-Doped Carbon Nanotubes (M = Fe, Ni, Cu) Hydrogen Evolution Hybrid Catalysts

The enhancement of catalytic performance of cobalt phosphide-based catalysts for the hydrogen evolution reaction (HER) is still challenging. In this work, the doping effect of some transition metal (M = Fe, Ni, Cu) on the electrocatalytic performance of the M-Co2P/NCNTs (NCNTs, nitrogen-doped carbon nanotubes) hybrid catalysts for the HER was studied systematically. The M-Co2P/NCNTs hybrid catalysts were synthesized via a simple in situ thermal decomposition process. A series of techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma-optical emission spectrometry, transmission electron microscopy, and N2 sorption were used to characterize the as-synthesized M-Co2P/NCNTs hybrid catalysts. Electrochemical measurements showed the catalytic performance according to the following order of Fe-Co2P/NCNTs > Ni-Co2P/NCNTs > Cu-Co2P/NCNTs, which can be ascribed to the difference of structure, morphology, and electronic property after doping. The doping of Fe atoms promote the growth of the [111] crystal plane, resulting in a large specific area and exposing more catalytic active sites. Meanwhile, the Fe(δ+) has the highest positive charge among all the M-Co2P/NCNTs hybrid catalysts after doping. All these changes can be used to contribute the highest electrocatalytic activity of the Fe-Co2P/NCNTs hybrid catalyst for HER. Furthermore, an optimal HER electrocatalytic activity was obtained by adjusting the doping ratio of Fe atoms. Our current research indicates that the doping of metal is also an important strategy to improve the electrocatalytic activity for the HER.

Robustly photogenerating H2 in water using FeP/CdS catalyst under solar irradiation

Photosplitting water for H₂ production is a promising, sustainable approach for solar-to-chemical energy conversion. However, developing low-cost, high efficient and stable photocatalysts remains the major challenge. Here we report a composite photocatalyst consisting of FeP nanoparticles and CdS nanocrystals (FeP/CdS) for photogenerating H₂ in aqueous lactic acid solution under visible light irradiation. Experimental results demonstrate that the photocatalyst is highly active with a H₂-evolution rate of 202000 μmol h⁻¹ g⁻¹ for the first 5 h (106000 μmol h⁻¹ g⁻¹ under natural solar irradiation), which is the best H₂ evolution activity, even 3-fold higher than the control in situ photo-deposited Pt/CdS system, and the corresponding to an apparent quantum efficiency of over 35% at 520 nm. More important, we found that the system exhibited excellent stability and remained effective after more than 100 h in optimal conditions under visible light irradiation. A wide-ranging analysis verified that FeP effectively separates the photoexcited charge from CdS and showed that the dual active sites in FeP enhance the activity of FeP/CdS photocatalysts.

Improved photoactivity of TiO2–Fe2O3 nanocomposites for visible-light water splitting after phosphate bridging and its mechanism

The phosphate bridges built are favorable for charge transfer and separation, leading to a greatly-enhanced photoactivity for water splitting.

FeP nanoparticles film grown on carbon cloth: an ultrahighly active 3D hydrogen evolution cathode in both acidic and neutral solutions

In this Letter, we demonstrate the direct growth of FeP nanoparticles film on carbon cloth (FeP/CC) through low-temperature phosphidation of its Fe3O4/CC precursor. Remarkably, when used as an integrated 3D hydrogen evolution cathode, this FeP/CC electrode exhibits ultrahigh catalytic activity comparable to commercial Pt/C and good stability in acidic media. This electrode also performs well in neutral solutions. This work offers us the most cost-effective and active 3D cathode toward electrochemical water splitting for large-scale hydrogen fuel production.

NiP₂ nanosheet arrays supported on carbon cloth: an efficient 3D hydrogen evolution cathode in both acidic and alkaline solutions

Designing efficient and stable hydrogen evolution catalysts made from earth-abundant elements is essential to the development of solar-driven water-splitting devices. In this communication, we develop a two-step strategy for constructing NiP2 nanosheet arrays on carbon cloth (NiP2 NS/CC). As a novel 3D hydrogen evolution cathode, the NiP2 NS/CC electrode is highly active in acidic solutions and needs an overpotential of 75 and 204 mV to achieve current densities of 10 and 100 mA cm(-2), respectively, and it preserves its catalytic activity for at least 57 h. Moreover, it also operates efficiently under alkaline conditions.