PH3 Decomposition Research Articles

Synergistic role of Co and CoP on highly dispersed cobalt nanoparticles embeded in porous carbon for efficient PH3 decomposition

Efficient resourceful treatment of phosphine tail gas is a huge challenge. In this study, a series of cobalt nanoparticles embeded in porous carbon (Co@C) catalysts were obtained via pyrolysis of Co-based MOF as precursor for catalytic decomposition of phosphine (PH3) by regulating the ratio of reactants of MOFs. The composition, morphology and structure of the catalysts were characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and BET measurement. The effect of Co@C catalysts with different reactant ratio on the catalytic decomposition of PH3 was tested, and the catalysts before and after the reaction were compared. It was found that the catalyst with MOF as the precursor after pyrolysis can still retain the porosity and large specific surface area of MOF. The metal cobalt nanoparticles and its oxides can be uniformly distributed in time under high loading, which is conducive to the reaction with phosphine to form metal phosphide (CoP), and the rapid and efficient decomposition of PH3 was completed under the synergistic effect of the two kinds of active sites of Co and CoP. The best catalytic decomposition efficiency is Co@C-5 catalyst, which can achieve 100 % decomposition efficiency at 350 °C and has good stability.

A Shock-Tube Study of the Rate Constant of PH3 + M ⇄ PH2 + H + M (M = Ar) Using PH3 Laser Absorption.

Phosphine (PH3) is a highly reactive and toxic gas. Prior experimental investigations of PH3 pyrolysis reactions have included only low-temperature measurements. This study reports the first shock-tube measurements of PH3 pyrolysis using a new PH3 laser absorption technique near 4.56 μm. Experiments were conducted in mixtures of 0.5% PH3/Ar behind reflected shock waves at temperatures of 1460-2013 K and pressures of ∼1.3 and ∼0.5 atm. The PH3 time histories displayed two-stage behavior similar to that previously observed for NH3 decomposition, suggesting by analogy that the rate constant for PH3 + M ⇄ PH2 + H + M (R1) could be determined. A simple three-step mechanism was assembled for data analysis. In a detailed kinetic analysis of the first-stage PH3 decomposition, values of k1,0 were obtained and best described by (in cm3·mol-1·s-1) k1,0 = 7.78 × 1017 exp(-80,400/RT), with units of cal, mol, K, s, and cm3. Agreement between the 1.3 and 0.5 atm data confirmed that the measured k1,0 was in the low-pressure limit. Agreement of the experimental k1,0 with ab initio estimates resolved the question of the main pathway of PH3 decomposition: it proceeds as PH3 ⇄ PH2 + H instead of PH3 ⇄ PH + H2.

Catalytic decomposition of toxic phosphine gas on the developed nickel ferrite nanocrystals supported by Halloysite nanotubes

Nickel ferrite (NiFe2O4) nanocatalysts with trace metal nickel (Ni0) as the reaction trigger were dispersedly supported by halloysite nanotubes (HNTs) to decompose toxic phosphine (PH3) into yellow phosphorus and hydrogen. The mixed spinel catalyst greatly reduced the temperature to 400 °C for 99% conversion and underwent no obvious deactivation after 2 h compared with magnetite. The as-synthesized and spent catalysts were characterized by Transmission electron microscope, X-ray powder diffraction and X-ray photoelectron spectroscopy. In combination with density functional theory calculations, the PH3 decomposition mechanism on Ni0@NiFe2O4/HNTs was proposed. The original plated Ni0 triggers the reaction to form active H radicals ([▾H]) contributing to the reduction of octahedral Ni(II) in NiFe2O4, and the newly generated Ni0 determines the catalytic activity and stability. In addition, the formation of Ni2P is crucial to developing the stable elemental phosphorus (P) layer as the mainly active intermediate for PH3 successive decomposition into P4, since P layer reduces the activation barrier of PH3 decomposition. Particularly, the mixed crystal spinel with specific coordination (with octahedral coordinated Fe(II) and tetrahedral coordinated defects) facilitates the electron transfer among the active species to recycle the catalytic reaction. This work provides a promising approach for PH3 air-pollution control and P recovery from the industrial off-gas.

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

ABSTRACT 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.

Optical emission spectroscopy of gallium phosphide plasma-enhanced atomic layer deposition

The capability of optical emission spectroscopy for in situ study and control of plasma-enhanced atomic-layer deposition (PE-ALD) of gallium phosphide from phosphine and trimethylgallium carried by hydrogen was explored. The gas composition changing during the PE-ALD process was monitored by in situ measurements of optical emission intensity for phosphine and hydrogen lines. For PE-ALD process where phosphorus and gallium deposition steps are separated in time a negative influence of excess phosphorus accumulation on the chamber walls was observed. Indeed, the phosphorus deposited on the walls during PH3 decomposition step is etched by hydrogen plasma during the next trimethylgallium decomposition step leading to uncontrollable and unwanted conventional plasma-enhanced chemical vapor deposition. To reduce this effect, it has been proposed to introduce a step of hydrogen plasma etching, which allows one to etch excess phosphorus before the beginning of gallium deposition step and achieve atomic-layer deposition growth mode.

Catalytic Decomposition of Toxic Chemicals Over Iron Group Metals Supported on Carbon Nanotubes

This study explores catalytic decomposition of phosphine (PH3) using iron group metals (Co, Ni) and metal oxides (Fe2O3, Co(3)O4, NiO) supported on carbon nanotubes (CNTs). The catalysts are synthesized by means of a deposition-precipitation method. The morphology, structure, and composition of the catalysts are characterized using a number of analytical instrumentations, including high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurement, and inductively coupled plasma. The activity of the catalysts in the PH3 decomposition reaction is measured and correlated with their surface and structural properties. The characterization results show that phosphidation occurs on the catalyst surface, and the resulting metal phosphides act as an active phase in the PH3 decomposition reaction. Cobalt phosphide, CoP, is formed on Co/CNTs and Co(3)O4/CNTs, whereas iron phosphide, FeP, is formed on Fe2O3/CNTs. In contrast, phosphorus-rich phosphide NiP2 is formed on Ni/CNTs and NiO/CNTs. The initial activities of the catalysts are shown in the following sequence: Ni/CNTs > Co/CNTs > Co(3)O4/CNTs >NiO/CNTs > Fe2O3/CNTs, whereas activities of metal phosphides are shown in the following order: CoP > NiP2 > FeP. The catalytic activity of metal phosphides is attributed to their electronic properties. Cobalt phosphide formed on Co/CNTs and Co(3)O4/CNTs exhibits not only the highest activity, but also long-term stability in the PH3 decomposition reaction.

Halloysite-nanotubes supported FeNi alloy nanoparticles for catalytic decomposition of toxic phosphine gas into yellow phosphorus and hydrogen

The FeNi alloy nanoparticles (FeNi and BFeNi) supported on natural halloysite nanotubes (HNTs) were prepared for catalytic decomposition of toxic phosphine (PH3) to yellow phosphorus and hydrogen. The Fourier transform infrared spectroscopy, X-ray diffraction, inductively coupled plasma, scanning electron microscope, and hydrogen temperature-programmed reduction tests were carried out to characterize the physicochemical properties of HNTs and the prepared nano-catalysts. Nearly 100% PH3 was decomposed into yellow phosphorus and hydrogen at 420°C with prepared FeNi/HNTs catalysts. Metallic Ni and Fe3O4 could be the catalytic active sites in FeNi/HNTs for PH3 decomposition under the low temperature. The boron (B) additives decrease the catalytic activity of FeNi/HNTs for PH3 decomposition due to the formation of the spinal NiFe2O4 and Fe2B which replace the active Fe3O4 and metallic Ni in catalysts. The developed FeNi/HNTs are low-cost and effective catalysts for air-pollution control and recycle of the hazardous waste PH3 gas in industry.

Study of the phosphine plasma decomposition and its formation by ablation of red phosphorus in hydrogen plasma

Mass spectrometry and optical emission spectroscopy have been used to study the chemistry of PH3 plasma decomposition as well as its formation by ablation of red phosphorus in hydrogen plasma. It has been shown that PH3 decomposition easily equilibrates at low levels of PH3 depletion (15%–30 %), this depending mainly on the rf power. The ablation of red phosphorus in H2 plasma produces phosphine in significant amount, depending mainly on the total pressure but also on the rf power. It has also been found that H* and PH* emitting species originate not only by the dissociative excitation of H2 and PH3, respectively, but also by the direct excitation of the same species in the ground state. Considerations are developed on how to derive the H-atom and PH radical densities by actinometry, under specific experimental conditions. Besides, the linear dependence of PH3 formation rate, rPH3, on H-atom density, [H], leads to the definition of the kinetic equation rPH3=k[H], and to the hypothesis that the formation of PH radical on the surface or its desorption is the dominant mechanism for PH3 production.

PH3 surface chemistry on Si(111)-(7×7): A study by Auger spectroscopy and electron stimulated desorption methods

The adsorption and decomposition of PH3 on Si(111)-(7×7) was investigated in ultrahigh vacuum by means of temperature programmed desorption, low-energy electron diffraction, Auger electron spectroscopy (AES), and electron stimulated desorption (ESD) methods. Phosphine adsorbs on Si(111)-(7×7) at T=120 K with an initial sticking coefficient of S0≂1 through a mobile (extrinsic) precursor state. Some PH3 dissociative adsorption at 120 K is observed. Thermal activation of the adsorbed species results in desorption of a molecular PH3 species up to 550 K. Further heating produces H2(g) desorption at T≂740 K and P2(g) desorption at T≂1010 K, thus indicating that PH3 decomposition has occurred. AES and ESD studies of the adsorbed species reveal that decomposition takes place by the breaking of PH bonds in PHx(a) to form SiH species on the surface for 120 K<T<700 K.

CARS in situ diagnostics in MOVPE: The thermal decomposition of AsH3 and PH3

Coherent anti-Stokes Raman Scattering (CARS) is used to study the thermal decomposition of AsH3 and PH3 in a horizontal reactor for metalorganic vapor phase epitaxy (MOVPE) of III/V compound semiconductors. Both in situ diagnostics and ex situ sampling experiments are considered. The decomposition temperatures obtained from in situ experiments are much lower (300 to 400 K) than those measured by ex situ techniques. The ex situ data compare well to previously reported observations. The results indicate that the thermal decomposition of AsH3 and PH3 is complex involving gas phase and surface reactions. The large difference in decomposition behavior between the two measuring techniques also demonstrates the importance of in situ diagnostics and the difficulty in ex situ monitoring of MOVPE species concentrations. No change in AsH3 or PH3 decomposition behavior is observeed with the addition of TMG or TMI. Molecular hydrogen is detected as a decomposition product, however in concentrations which are lower than expected from complete hydride decomposition.

Surface chemistry of phosphorus-containing molecules: I. Interaction of PH3 with Rh(100) and the effect of preadsorbed phosphorus

The interaction of PH3 with Rh(100) has been investigated using temperature-programmed desorption spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, and work function change measurements. A mobile precursor state is involved in the adsorption kinetics at 100 K. The overlayer is saturated after an exposure of 3 L, at which point the work function has decreased by 1.2 eV, indicating adsorption through the phosphorus atoms. Heating the crystal above 100 K desorbs molecular PH3 and H2, and leaves adsorbed phosphorus atoms on the surface. The PH3 thermal desorption spectra show a coverage-dependent adsorption energy associated with repulsive lateral interactions between the adsorbed molecules. There are two thermal desorption states of hydrogen, one of which is characteristic of hydrogen on clean Rh(100). Preadsorbed phosphorus atoms partially passivate the surface, preventing PH3 decomposition until higher temperatures are reached. Preadsorbed phosphorus also reduces the capacity of the surface for H2 adsorption, but does not alter the activation energy for H2 desorption.