Stability For Methanol Oxidation Reaction Research Articles

Revealing the mechanism of bifunctional PtLa electrocatalyst for highly efficient methanol oxidation, hydrogen evolution, and coupling reaction

The development of clean energy solutions, such as fuel cells and hydrogen energy, is crucial for addressing the global energy shortage. Platinum (Pt)-based catalysts are widely used in fuel cells and hydrogen energy generation (for example, via water electrolysis). However, reducing the amount of Pt used while maintaining the catalytic performance of such catalysts is essential. Herein, PtLa catalysts (PtxLay/C) doped with rare earth element lanthanum (La) with different Pt/La atomic ratios were synthesized using a simple chemical reduction method, resulting in Pt65La35/C, Pt78La22/C, Pt97La3/C, and Pt100/C. These PtxLay/C catalysts exhibited excellent electrocatalytic activity and stability in methanol oxidation reaction (MOR), hydrogen evolution reaction (HER), and their coupling reaction as MOR||HER under alkaline conditions. The mechanism by which La doping enhances the electrocatalytic properties and stability of Pt-based catalysts was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), aberration-corrected scanning transmission electron microscopy (AC-STEM), in-situ Fourier transform infrared (FTIR) and operando Raman spectroscopy. For HER, La doping facilitated the adsorption and activation of H2O at Pt sites, improving water dissociation and *OH desorption and reducing Pt poisoning by *OH. This enhances both the catalytic performance and stability of PtxLay/C for HER. Pt78La22/C exhibited a considerably lower overpotential of only 111 mV at 100 mA cm−2 compared to commercial 20 wt% Pt/C (Pt/C-Johnson Matthey (JM)), which requires 153 mV. For MOR, La promotes CO bond cleavage and reduces CO adsorption at the Pt sites, thereby enhancing both the performance and stability of the catalysts. The mass activity (MA) of Pt78La22/C for MOR is 4.44 A mg−1Pt, which is 12.33 times higher than that of Pt/C-JM (0.36 A/mgPt), and surpasses those of Pt65La35/C, Pt97La3/C, and Pt100/C (2.93, 0.24, and 2.91 A mg−1Pt, respectively). Additionally, Pt78La22/C exhibited outstanding catalytic performance for MOR||HER, with a current density of 20 mA cm−2 at 1.030 V, demonstrating good stability with negligible voltage changes after a 15 h chronoamperometry (CA) testing. This study provides a new strategy for synthesizing Pt-based catalysts with enhanced efficiency and low-energy input for HER||MOR.

Dendritic Pt Aerogel for Highly Efficient Electrocatalytic Methanol Oxidation Reaction

AbstractMetallic aerogels, as featured by high surface area, porosity, and self‐supported metal skeleton, are regarded as an ideal platform for developing next‐generation electrocatalysts. However, the precise adjustment of their skeleton nanostructure to enhance catalytic properties remains significantly underexplored. Herein, inspired by the impact of the metal atoms’ coordination number on their reactivity, we devised and prepared dendritic Pt aerogels (DPAs) via a facile sol‐gel method. The synergy of aerogel structure and coordinatively distinct catalytic sites from dendritic morphology enables DPAs to exhibit markedly improved electrocatalytic activity and stability for methanol oxidation reaction. The mass activity and specific activity of DPAs are 1.28 A mgPt−1 and 1.5 mA cmPt−2, which are 4.1 and 3.2 times higher than those of commercial Pt/C, respectively.

Enhanced Electrocatalytic Performance of the FePt/PPy-C Composite toward Methanol Oxidation.

A novel FePt/PPy-C composite nanomaterial has been designed and investigated as a methanol oxidation reaction (MOR) electrocatalyst. The FePt nanoparticles with an average diameter of about 3 nm have been prepared by the co-reduction method and then loaded onto the PPy-C composite support. The electrocatalytic performance is affected by the composition of the FePt nanoparticles. The experimental results indicated that the Fe1.5Pt1/PPy-C catalyst exhibited excellent catalytic activity and stability for MOR, with mass activity and specific activity of 1.76 A mgPt-1 and 2.71 mA cm-2, respectively, which are 5.18 and 4.60 times higher than that of the commercial Pt/C catalyst. Density functional theory (DFT) has been employed to simulate the electrical structures of catalyst supports, and the mechanism of the methanol oxidation process has been further analyzed. The heterojunctions of the PPy-C interface could accelerate the electron migration from the electrocatalytic center to the electrodes. The possibility of methanol oxidation has been improved effectively, which can be confirmed by the d-band center and CO adsorption energy on FePt nanoparticles in the DFT calculation results.

Insights into the roles of nitrogen and phosphorus co-doping for efficient methanol electrooxidation

Anchoring Pt onto multi-heteroatom doped carbon materials has been recognized as an effective approach to improve the performance of electrocatalytic methanol oxidation. However, distinct contributions and specific behavior mechanisms of different heteroatoms, notably N and P, the specific behavior mechanisms in synergistically promoting Pt NPs remain elusive. In this work, we construct 1D N and P co-doped carbon nanotube (N, P-CNTs) supports with abundant defect anchors for Pt. The as-prepared Pt/N, P-CNTs exhibit outstanding activity and exceptional stability in methanol oxidation reaction (MOR), achieving high mass activity up to 6481.3 mA mg−1Pt. Moreover, they can retain 90.5 % of their initial current density even after 800 cycles tests. Detailed characterizations and theoretical calculations indicate that the robust strong metal-support interactions (SMSI) effect caused by N doping within the unique N and P co-doped coordination structure controllably regulate the coordination environment of Pt, reduce the d-band center of Pt, thus promoting the adsorption and decomposition of CH3OH. However, P doping weakens the adsorption strength of CO on the Pt active site by sacrificing partial electron transfer, accelerating the oxidative conversion of the CO-like poisoning species (COads). Significantly, the synergistic mechanism of N and P species on the modification of Pt’s electronic structure and its subsequent impact on the electrocatalytic methanol oxidation behaviors on the Pt surface was thoroughly elucidated, providing a constructive route for designing robust MOR electrocatalysts with high MOR activity and durability.

In situ growth of Ni/Ni3S2–MoO2 nanocrystals on carbon cloth for the enhanced electrocatalytic oxidation of methanol

The rational design and construction of high-performance Ni-based methanol oxidation catalyst is the key technology for direct methanol fuel cell (DMFC). In this work, Ni/Ni3S2–MoO2@CC composite is constructed by in-situ growth of Ni/Ni3S2–MoO2 nanoparticles on carbon cloth (CC) by a two-step method, which has excellent activity and stability for methanol oxidation reaction (MOR), that is, the current density (j) can reach 240.08 mA cm−2 at the potential of 1.67 V. The potentials at different j are 10 mA cm−2@1.37 V and 100 mA cm−2@1.50 V, respectively. Meanwhile, the retention rate of j is 90.36 % after 12 h CA stability test. Based on density functional theory (DFT) calculation, the excellent properties of Ni/Ni3S2–MoO2@CC composite are mainly attributed to its higher conductivity and higher carrier density accelerate the charge transfer in the MOR process, its Ni and Mo sites facilitate the adsorption of methanol as a reactant and desorption of carbon dioxide as a product, thus promoting the kinetics of MOR. In addition, the reaction mechanism of MOR on the Ni/Ni3S2–MoO2@CC is more likely to follow the formation path of CO* intermediates. This work provides a feasible route for the synthesis of high performance electrocatalysts for the MOR.

Selectively coupling Ru single atoms facilitating methanol oxidation reaction

Direct methanol fuel cells (DMFCs) are highly sensitive to CO poisoning on the current Pt based anode at operating condition. In a paper recently published in Angewandte Chemie International Edition, Kong et al. and coworkers presented a precise position control of single atom via atomic layer deposition (ALD) to synthesis the selective deposition of Ru single atoms (SAs) on the concavities of corrugated PtNi nanoparticles (Ru-ca-PtNi), which exhibited high activity and stability for methanol oxidation reaction (MOR).

Ni3S4/NiS/rGO as a promising electrocatalyst for methanol and ethanol electro-oxidation

We present a one-step hydrothermal synthesis of hybrids consisting of nickel sulfides in the form of Ni3S4–NiS (NN) and Ni3S4–NiS-rGO (NNR), i.e. with the addition of reduced graphene oxide (rGO), for application as catalysts. After accurate physical characterization and confirmation of successful synthesis, we evaluate the ability of these catalysts in the processes of methanol and ethanol oxidation. The precise electrochemical analyses show relatively good potential and excellent cyclic stability in methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) processes. The comparison of the two catalysts shows the superiority of NNR over NN, confirming that rGO introduces a higher specific surface area and a higher electrical conductivity in the NNR structure. In the process of MOR, NNR has an oxidation peak at a current density of 55 mA cm−2 and a peak potential of 0.54 V. In EOR, this peak is located at a current density of 11 mA cm−2 and at a peak potential of 0.59 V. NNR has 97% and 94% stability in MOR and EOR after 1000 consecutive cycles, respectively, which are acceptable values.

Preparation of Pt catalysts supported on polyaniline modified carbon black and electrocatalytic methanol oxidation

The supports are of vital importance for supported catalysts. In this work, an excellent anode catalyst support for methanol oxidation reaction is prepared by using polyaniline (PANI) surface modified carbon black (CB), and Pt catalysts are supported on the surface of carbon black modified by polyaniline (Pt/PANI-CB). The characterizations of structure and morphology show that Pt nanoparticles with an average diameter of 2.89 nm are uniformly dispersed on the surface of carbon black modified by polyaniline. Compared with Pt supported on the surface of carbon black (Pt/CB) and commercial Pt/C catalysts, the optimal Pt/PANI-CB has higher electrocatalytic activity, and better stability for methanol oxidation reaction. In 0.5 M H2SO4 solution containing 0.5 M CH3OH, the area specific activity of Pt/PANI-CB is 1.81 mA cm−2Pt, and those of Pt/CB and Pt/C is 1.29 and 0.68 mA cm−2Pt. After 1000 cycles of cyclic voltammetry, the area specific activity retention of Pt/PANI-CB is 74.0%, while those of Pt/CB and Pt/C are 60.4% and 38.2%. Obviously, as a catalyst support, carbon black modified by polyaniline has broad application prospects.

Composition-tunable synthesis of Pt-Cu dendritic nanomaterials by ultrasound-assisted approach for highly efficient methanol oxidation

The exploration of simple and green synthetic methods and realization of facile composition tuning of nanomaterials are key to achieve high catalytic activity. Herein, we successfully achieve a one-pot synthesis of composition-tunable PtCu bimetallic nanodendrites in aqueous solution by an ultrasound-assisted approach, in which ultrasound plays an important role in the nanoparticle growth. After complete removal of surface ligand, these PtCu nanodendrites show very high catalytic activity and stability for methanol oxidation reaction.

N-Doped Carbon Nanotube Shell Encapsulating the NiFe Metal Core for Enhanced Catalytic Stability in Methanol Oxidation Reaction by the Structural Cooperation Mechanism.

Exploitation of high-efficiency catalysts toward methanol oxidation is a pivotal step to promote the commercialization of direct methanol fuel cells. Herein, a strategy is demonstrated to prepare nitrogen-doped carbon nanotubes with NiFe metal particles (NiFe@N-CNT) as the carrier material of Pt nanoparticles. Combining SEM and TEM, NiFe metal particles are fully encapsulated in N-CNTs, and they form the metal core and carbon nanotube shell structure based on the structural cooperation mechanism. Surprisingly, the as-prepared Pt/NiFe@N-CNT catalyst shows superior catalytic activity (1023 mA mg-1Pt) compared to commercial Pt/C (392 mA mg-1Pt), Pt/Ni@N-CNT (331 mA mg-1Pt), and Pt/Fe@N-CNT (592 mA mg-1Pt). After 1000 cycles, Pt/NiFe@N-CNT maintains the optimal catalytic activity (588 mA mg-1Pt), and its mass activity loss is 42.5%, which is better than those of commercial Pt/C (64.0%), Pt/Ni@N-CNT (67.7%), and Pt/Fe@N-CNT (59.6%) catalysts, indicating that the Pt/NiFe@N-CNT catalyst achieves excellent catalytic activity and stability, which stems chiefly from the homodispersed Pt nanoparticles and the generation of the metal core-carbon nanotube shell based on the structural cooperation mechanism. This study reports the facile construction of a metal core-carbon nanotube shell structure, which intrinsically ameliorates structural collapse of carrier material, thereby improving the catalytic stability of the Pt-based catalyst and broadening the view for design of other desire catalysts in methanol oxidation.

Well-dispersive Pt nanocrystals anchored onto 3D boron and nitrogen double-doped reduced graphene oxide–carbon nanotube frameworks as efficient electrocatalysts for methanol oxidation

A bottom-up self-assembly method is developed to the fabrication of well-dispersive Pt nanocrystals anchored onto 3D B and N double-doped reduced graphene oxide-CNT frameworks, which express superior electrocatalytic performance for methanol oxidation. • 3D B and N double-doped graphene-CNT frameworks are fabricated via a co-assembly strategy; • The homogeneous distribution of Pt nanocrystals on the hybrid frameworks is realized; • The interconnected porous network and optimized electronic structure provide numerous active sites; • The as-derived catalysts express exceptional electrochemical performance toward methanol oxidation. The development of direct methanol fuel cell (DMFC) technology is an effective way to solve the problems of environmental pollution and energy shortage, while the scarcity of the highly-efficient anode catalysts with low cost severely limits its commercial use. In this work, we report a robust and convenient approach for the bottom-up construction of well-dispersive Pt nanocrystals anchored onto three-dimensional (3D) porous boron and nitrogen double-doped reduced graphene oxide–carbon nanotube frameworks (Pt/BNRGO-CNT) via a controllable co-assembly process. This architectural design can achieve a series of useful structural merits, such as 3D cross-linked porous network, large presence of B and N atoms, homogeneous Pt dispersibility, and high electrical conductivity. Consequently, the resulting Pt/BNRGO-CNT electrocatalysts exhibit excellent catalytic activity, strong anti-toxicity ability, and good long-term stability for methanol oxidation reaction, far exceeding those of Pt catalysts supported by the conventional undoped reduced graphene oxide, carbon nanotube, and carbon black matrixes.

Fabrication of amorphous PdNiCuP nanoparticles as efficient bifunctional and highly durable electrocatalyst for methanol and formic acid oxidation

• We utilize a facile laser liquid ablation method to synthesize amorphous PdNiCuP. • The amorphous PdNiCuP is highly efficient and stable for both MOR and FAOR. • The amorphous PdNiCuP displays superior anti-poisoning ability. Highly active and durable electrocatalytic materials towards small molecules electro-oxidation reaction are critical to the large-scale commercial applications of direct liquid fuel cells. Unfortunately, current nanocrystalline electrocatalysts normally suffer from low catalytic efficiency, severe CO poisoning and rapid activity decay. Herein, we report a novel amorphous PdNiCuP catalyst synthesized with laser liquid ablation as a potential settlement to this issue. The as-obtained amorphous PdNiCuP catalyst exhibits enhanced electrocatalytic performance with the mass activity of 1.61 A mg −1 and 737.8 mA mg −1 towards methanol oxidation reaction (MOR) and formic acid oxidation reaction (FAOR), respectively. Moreover, amorphous PdNiCuP displays excellent operation stability and CO-poisoning resistance in both alkaline and acidic medium. P was proposed to play the decisive role for forming the amorphous structure and maintaining the catalytic stability in MOR and FAOR processes. This work provided insights for the ration design of active and durable amorphous electrocatalysts applied in direct liquid fuel cells.

An effective Pt–CoTe/NC catalyst of bifunctional methanol electrolysis for hydrogen generation

Hydrogen production from water electrolysis is seriously restricted by the high energy consumption caused by water oxidation. Herein, an effective low-energy input for hydrogen generation via methanol-assisted water electrolysis catalyzed by bifunctional Pt–CoTe/NC nanospheres is demonstrated, which can be obtained by the ZIF-67 derived CoTe/NC supported ultrafine Pt nanoparticles. The experimental and density functional theory calculation analysis indicated that the optimized electronic structure of Pt–CoTe/NC modifies the adsorption energies of the intermediate (CO and H*), which exhibits superior catalytic activity and stability for methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER). For MOR, the current density of Pt–CoTe/NC-800 is 102.2 mA cm−2, which is 3.7 times that of commercial Pt/C catalyst, and high anti-poisoning ability is also found in the CO-stripping technique. Moreover, the small overpotential of 28 mV is required to deliver a current density of 10 mA cm−2 for HER. When the optimal Pt–CoTe/NC serves as both cathode and anode in a two-electrode electrolyzer for methanol electrolysis, a low cell potential of 0.68 V is required to reach 10 mA cm−2, about 960 mV lower than that of water electrolysis, and the performance is also much better than that of Pt/C||Pt/C electrode system. The current work offers a robust platform of bifunctional catalyst for MOR coupled with HER for hydrogen generation.

Electrosynthesis of dendritic palladium supported on Ti/TiO2NTs/Ni/CeO2 as high-performing and stable anode electrocatalyst for methanol electrooxidation

Liquid-fueled direct methanol fuel cell (DMFC) is highly promising for low-carbon transportation, but is hindered by high cost and short lifespan of conventional Pt-based electrocatalysts. Herein, we propose a new Pt-free catalyst strategy to exploit high-performing and stable electrocatalyst of DMFC, achieving enhanced electrocatalytic activity and high stability for methanol oxidation reaction (MOR) in alkaline media. A new Pt-free anode catalysts consisting of titanium/reduced-titanium dioxide nanotubes/nickel/cerium dioxide (Ti/r-TiO2NTs/Ni/CeO2) nanosupport and uniformly-dispersed Pd dendrites is successfully prepared by a facile three-step electrodeposition route without applying any template or surfactant. Noticeably, the as-prepared Ti/r-TiO2NTs/Ni/CeO2–Pd as an anode electrode exhibits superior activity than commercial Pd/C and other electrodes. The obtained large mass activity for Ti/r-TiO2NTs/Ni/CeO2–Pd electrode is 1752 mA mgPd−1 for MOR. After successive CV tests of 1000 cycles, Ti/r-TiO2NTs/Ni/CeO2–Pd electrode still retained 88.9% of its initial current. The superior performance of Ti/r-TiO2NTs/Ni/CeO2–Pd attributes to the large surface area and excellent conductivity, as well as the synergistic effects among nanosupport and Pd dendrites. Therefore, this study will open a new door for high-performance fuel cell applications.

Silk‐Derived N‐Doped Fe@NPC as Efficient Bifunctional Electrocatalyst for Direct Methanol Fuel Cell (DMFC)

AbstractThe development of economic and efficient bifunctional electrocatalysts, which can boost both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) is quite necessary for the evolution of direct methanol fuel cell (DMFC). Herein, a novelty of precious metal‐free, iron, nitrogen and phosphorus‐doped porous carbon (Fe@NPC) was prepared by using cheap and renewable biomass silk as basic nitrogen sources, as an efficient ORR and MOR electrocatalyst with its high nitrogen content (8.16 wt%). The Fe@NPC catalyst exhibits extremely high onset potential (1.125 V vs RHE), current density (−6.089 mA cm−2) and methanol tolerance for ORR, even exceeds the corresponding values of Pt/C (1.007 V vs RHE, 5.068 mA cm−2). Furthermore, it also served as a good carrier for Pt nanoparticles (NPs). Pt/Fe@NPC shows high catalytic activity and stability for MOR in acidic condition.

Facile synthesis of N-doped carbon nanotubes grafted on N-doped carbon nanosheets co-encapsulating cobalt and molybdenum carbide nanoparticles for efficient methanol oxidation

Developing efficient electrocatalysts based on inexpensive and environment protection materials for methanol oxidation reaction (MOR) is crucial to new generation renewable energy storage and conversion processes, but it remains a major challenge. In our current research, N-doped carbon nanotubes grafted on N-doped carbon nanosheets co-encapsulating cobalt and Mo2C nanoparticles (Co-Mo2C/NCNT@NCN) are designed and synthesized by simple mixing and one-step annealing approach. After depositing Pt nanoparticles, Pt/Co-Mo2C/NCNT@NCN exhibits superior catalytic activity and stability for MOR in acid medium; more precisely, it has a commendable mass activity of 842 mA/mgPt, which is 2.1 times of Pt/C-JM. And it is worth mentioning that its anti-CO poisoning ability and stability have also a visible improvement; the enhanced catalytic performance mainly benefits from the rich N doping, excellent structural features, and the synergistic effect of Co and Mo2C. Therefore, this study opens up a new direction for designing and developing a favorable active multicomponent catalyst for MOR.

Atomic Layer Deposition of NiO on Self‐Supported Co3O4 Nanoneedle Array for Electrocatalytic Methanol Oxidation Reaction

Developing efficient transition metal oxide catalysts is still challenging for direct methanol fuel cells. Herein, an atomic layer deposition method to prepare NiO on a self‐supported Co3O4 nanoneedle array grown on a porous nickel foam substrate (NiO–Co3O4 NA@NF) as the electrode for the methanol oxidation reaction (MOR) is reported. The synergistic effect between the NiO and Co3O4 components as well as the specific 3D nanoarray structure can endow the prepared NiO–Co3O4 NA@NF with a very promising MOR catalytic activity. As a result, the NiO–Co3O4 NA@NF catalyst shows a low onset potential (1.27 V vs reversible hydrogen electrode [RHE]), a high current density (173 mA cm−2@1.524 V vs RHE), and good stability in MOR. This work demonstrates the feasibility of the atomic layer deposition strategy in fabricating complex oxides‐based high‐performance electrocatalysts.

In-situ loading synthesis of graphene supported PtCu nanocube and its high activity and stability for methanol oxidation reaction

A perfect PtCu nanocube with partial hollow structure was prepared by hydrothermal reaction and its electrocatalytic methanol oxidation reaction (MOR) was studied. The appropriate concentration of shape-control additives KI and triblock pluronic copolymers, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO19-PPO69-PEO19) (P123) play crucial roles in the final product morphology. The PtCu nanocubes can be perfectly in situ immobilizedonto graphene under the action of P123 while the structure and cubic morphologyremain unchanged. The electrochemical tests suggest that the obtained PtCu nanocube (PtCu-NCb) exhibits better MOR activity and stability than PtCu hexagon nanosheet (PtCu-NSt), PtCu nanoellipsoid (PtCu-NEs) and commercial Pt/C in alkaline medium. When in situ immobilized onto graphene, the MOR catalytic activity and stability of PtCu cubes are further improved. The markedly enhanced electrocatalytic activity and durability maybe attributed to the special cubic morphology with partial hollow structure enclosed by highly efficient facet and the probably the synergistic effect of PtCu and intermediate state CuI decorated on the surface and graphene.

Synthesis of metal oxide nanoparticles doped poly 3 anisidine nanocomposites with enhanced electrocatalytic activity for methanol oxidation

We have explored the nanocomposites as a potential catalyst material in acid medium for the electro-oxidation of methanol. Electrochemical impedance studies have shown that the Rct value of (Poly-3-Anisidine) P3A/GCE is lower than the modified P3A-metal oxide doped electrodes. In the case of doped metal oxides, we claim, this validates the slow electron transfer mechanism. Compared to P3A-MnO2, P3A-Fe2O3 catalysts, the as-synthesized P3A-Cr2O3 displays an expanded electrochemically active surface region, substantially enhanced catalytic activity and improved stability for methanol oxidation reaction (MOR).

Facile one-pot synthesis of CuO nanosheet for application as electrocatalyst for methanol oxidation

Herein, a simple single step procedure for synthesis of CuO nanosheets (CuO-NS) at room temperature is reported. The structural and morphological evaluation proves that material is highly crystalline in nature. The electrocatalytic activity of CuO-NS for CH3OH oxidation was evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry methods in 0.5 M NaOH. The prepared catalyst showed comparable performance in terms of electrocatalytic current in comparison with reported electrodes modified with various transition metal-oxides. The electrochemical studies on CuO-NS reveal intriguing methanol electrooxidation properties with current density of 4.24 mA/cm2 and 75% current retention even after 2000 s, demonstrating its stability in methanol oxidation reaction (MOR). The improved activity of the electrocatalyst is due to mesoporosity and high surface area. Reaction kinetics and mechanism for CH3OH oxidation were studied. Double step chronoamperometric technique shows that CH3OH oxidation was irreversible. The results elucidate superior performance of the prepared catalyst for CH3OH oxidation and are notably promising in direct methanol fuel cell applications.