Photoelectrochemical C–H activation of methane to methyl radical at room temperature

Amano, Fumiaki; Shintani, Ayami; Sakakura, Tatsuya; Takatsuji, Yoshiyuki; Haruyama, Tetsuya

doi:10.1039/d3cy00632h

Cited by 7 publications

(17 citation statements)

References 41 publications

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“…The increased CO x formation rate implies that steam reforming of methane (CH 4 + x H 2 O → CO x + (2 + x )H 2 ) is promoted even at 25 °C. 24,25,39 C 2 H 6 is formed by CH 4 activation, implying the formation of methyl radicals and their coupling reaction. 40–43 The activation of the C–H bond of CH 4 is believed to be promoted by photogenerated holes and hydroxyl radicals.…”

Section: Resultsmentioning

confidence: 99%

“…14–16 The all-solid PEM-PEC system using porous photoanodes such as TiO 2 and WO 3 has also been employed in the CH 4 conversion reactions (steam reforming of methane and dehydrogenative coupling to ethane). 24,25 The selectivity for C 2 H 6 from CH 4 was more than 50% on a carbon basis for the ionomer-coated WO 3 photoanode under visible light irradiation.…”

Section: Introductionmentioning

confidence: 99%

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Gas-fed photoelectrochemical reactions sustained by phosphotungstic acid as an inorganic surface electrolyte

Amano,

Tsushiro,

Akamoto

2024

Energy Adv.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gas-fed photoelectrochemical reactions sustained by phosphotungstic acid as an inorganic surface electrolyte

Amano,

Tsushiro,

Akamoto

2024

Energy Adv.

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“…Gas-phase PEC cells that use porous photoelectrodes with integrated polymer electrolyte membranes have been investigated for vapor-fed water splitting (Figure 2C). [4,[14][15][16][17] The porous photoelectrode is attached to a proton-exchange membrane (PEM) and an anion-exchange membrane (AEM). Membrane photoelectrode assemblies have been successfully investigated for advanced PEC reactions without the use of liquid electrolytes.…”

Section: Microfiber-felt Substratesmentioning

confidence: 99%

“…Gas-phase methane conversion was demonstrated using a PEM-PEC cell with a gas-diffusion WO 3 photoanode under visible light (Figure 12B). [16,49] The gas-diffusion photoanode was composed of Ti felt covered with highly crystalline fine WO 3 particles (~100 nm) that interconnected to form a mesoporous structure. A PFSA ionomer was coated onto the surface of the structure to improve the proton conductivity of the bare WO 3 photoanode, thereby creating a triple-phase boundary between the semiconductor particles, ionomer, and methane gas (Figure 12C).…”

Section: Gas-fed Pem-pec Reactionsmentioning

confidence: 99%

Porous Transport Photoelectrodes Fabricated on Felt Substrates and Applications to Polymer Electrolyte Photoelectrochemistry

Amano,

Surya,

Singh

2024

ChemElectroChem

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Photoelectrochemistry is used to develop solar energy technologies for fuel production and chemical transformations. Semiconductor materials such as TiO2, WO3, BiVO4, Fe2O3, and Cu2O are often investigated in devices designed to convert light energy into chemical energy, including for the production of hydrogen by photoelectrochemical (PEC) water splitting. The oxide electrodes are of significant interest due to their potential for efficient PEC reactions with high durability and their relatively low costs compared to other semiconductor materials. This review highlights the roles played by macroporous photoelectrodes in the development of highly efficient photoelectrodes and advanced PEC systems using polymer electrolytes. Three‐dimensional conductive fiber substrates, such as titanium felt and carbon paper, outperform their two‐dimensional counterparts owing to their larger interfacial areas that enhance PEC properties. The macroporous structures facilitate mass‐transport‐limited reactions when integrated with polymer electrolytes in membrane electrode assemblies. Such configurations are promising for PEC splitting of pure water, and for transforming gaseous molecules such as water vapor, volatile organic compounds, and methane. Optimizing the configuration, including electrode materials selection and ionomer‐coating treatment, can potentially improve the performance of polymer electrolyte membrane PEC cells. Porous transport photoelectrodes integrated with proton/anion‐exchange membranes offer significant opportunities for advanced PEC applications.

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“…For the gas-phase methane activation, a porous WO 3 electrode was developed and functionalized with perfluoro sulfonic acid (PFSA) ionomer to facilitate proton transfer and transport on the gas-diffusion photoelectrode surface. 2,3,22,23 A proton exchange membrane (PEM) served as a solid electrolyte to manage the gaseous molecule at high concentrations, facilitating vapor-fed water splitting through integration with the functionalized macroporous photoanodes for oxygen evolution. 24,25 The photoexcited electrons move to the Pt−C catalyst cathode, reducing the number of protons to produce H 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

Photoelectrochemical Conversion of Methane to Ethane and Hydrogen under Visible Light Using Functionalized Tungsten Trioxide Photoanodes with Proton Exchange Membrane

Amano,

Suzuki,

Tsushiro

et al. 2024

ACS Appl. Mater. Interfaces

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Developing methane utilization technologies is desired to convert abundant and renewable carbon resources, such as natural gas and biogas, into valueadded chemical products. This study provides insights into emerging photoelectrochemical (PEC) technology for the photocatalytic transformation of methane to C 2 H 6 and H 2 using visible light at room temperature. The PEC conversion of methane to oxygenates has been investigated in aqueous electrolytes. Herein, we demonstrate the gas-phase PEC methane conversion using a proton exchange membrane (PEM) as a solid polymer electrolyte and a gas-diffusion photoanode for methane oxidation. Tungsten trioxide (WO 3 ), a semiconductor photocatalyst responsive to visible light, is utilized as the photoanode material. Ultraviolet light (∼365 nm) excitation predominantly results in CO 2 production with lower C 2 H 6 selectivity in humidified methane. In contrast, visible light (∼453 nm) effectively promotes C 2 H 6 production over the WO 3 photoanode, attributed to preferential hydroxyl radical ( • OH) formation compared to UV irradiation. Photogenerated holes formed near the valence band maximum of WO 3 contribute to • OH formation through a single-electron water oxidation. The photogenerated • OH activates gaseous methane molecules to methyl radicals, subsequently coupled into C 2 H 6 at the gas−electrolyte−semiconductor boundary. H 2 is concurrently formed on the cathode electrocatalyst. Improving the selectivity for the dehydrogenative coupling of methane is pivotal for enhancing the energy efficiency in the PEM−PEC system.

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Photoelectrochemical C–H activation of methane to methyl radical at room temperature

Abstract: Herein, we report a continuous gas-fed photoelectrochemical (PEC) system with a proton exchange membrane for CH4 activation at ambient temperature and pressure. We found that both water splitting and steam...

Cited by 7 publications

References 41 publications

Gas-fed photoelectrochemical reactions sustained by phosphotungstic acid as an inorganic surface electrolyte

Gas-fed photoelectrochemical reactions sustained by phosphotungstic acid as an inorganic surface electrolyte

Porous Transport Photoelectrodes Fabricated on Felt Substrates and Applications to Polymer Electrolyte Photoelectrochemistry

Photoelectrochemical Conversion of Methane to Ethane and Hydrogen under Visible Light Using Functionalized Tungsten Trioxide Photoanodes with Proton Exchange Membrane

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