Nanostructured Magnéli-Phase W18O49 Thin Films for Photoelectrochemical Water Splitting

Abstract

Converting water into hydrogen through the photo-electrochemical (PEC) process is one of the most exciting approaches in this field, and there is a quest to design or search for new electro-photo-catalytic materials. In this work, simple steps for fabrication and transformation of metallic tungsten thin film into the photo-active Magnéli-phase (W18O49) of tungsten oxide thin film is demonstrated. The post-annealing temperature has a significant impact on the phase evolution of tungsten film into W18O49. The film thickness of W18O49 is controlled by controlling the sputtering time (or deposition time) of W film. The PEC performance of the as-prepared electrodes is evaluated by monitoring the water oxidation reaction under visible radiation. The PEC findings reveal a correlation between PEC performance and phase, morphology, and thickness of the film. The as-derived W18O49 can efficiently catalyze the water oxidation reaction at neutral solution pH, generating 0.6 and 1.4 mA cm−1 photo-current at 0.6 and 0.8 V vs. Saturated calomel electrode (SCE), respectively, in addition to excellent stability. The electrical conductivity and the charge transfer kinetics are investigated employing the electrochemical impedance spectroscopic (EIS) technique.

Recent Progress in the Synthesis and Potential Applications of Two‐Dimensional Tungsten (Sub)oxides

“…The best responsivity (here, the input/ output ratio of the electrical resistance) to 40 ppb was reported to be 30, which is more than an order of magnitude higher than for the nanocrystals. [60] This work furthermore empha- Wet chemical [12] 200-1000 7-18 Monoclinic WO 3 (010) Water splitting nanodisks topochemical conversion [13] 200-500 10-30 Monoclinic WO 3 (001) Water splitting nanoplates hydrothermal [55] A few 100 ~10 Monoclinic WO 3 (200) NO 2 gas detection nanosheets Laser ablation [17] 600-1800 μm 30 Monoclinic WO 3 (001) / leaf-like nanoplatelets Aqueous Synthesis [19] Several 100 5-60 Hexagonal WO 3 (001) / nanosheets wet chemical [20] Up to 175 ~40 Orthorhombic WO 3 (010) CO oxidation nanoplatelets hydrothermal [21] < 200 nm 30-175 Triclinic WO 3 (100), ( 010), (001) Gas sensing nanosheets thermal decomposition [56] Up to a few 10 / W 18 O 49 (020) Photocatalytic decomposition nanosheets CVT [10] Up to 4000 10-100 W n O 3n-1 (001) / nanoplates direct current sputtering [49] / > 52 W 18 O 49 / water splitting film ALD [31a] / ~42 Monoclinic WO 3 (002) Gas sensor film Vapor-phase deposition [31b] 9-4 monolayer WO2 + O bilayer / / clusters sizes the influence of the stoichiometry on performance and properties. These materials were tested in the NO 2 concentration range of 20 to 2000 ppb, but the sample annealed at 225 °C was overly sensitive, reaching saturation beyond 120 ppb.…”

Dry Hydrogen Production in a Tandem Critical Raw Material-Free Water Photoelectrolysis Cell Using a Hydrophobic Gas-Diffusion Backing Layer

“…The existence of several concerns related to the increasing energy demand and the related environmental crisis [1][2][3][4][5][6] indicates the need to identify innovative, effective and low cost solutions. Photoelectrochemical water splitting (PWS) [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] is recognised as a promising strategy and it attracts particular interest for storing solar energy into the chemical bonds of hydrogen as fuel [26][27][28], which can be further utilised in fuel cells [29][30][31][32][33][34], internal combustion engines and to progressively decarbonize industrial processes [35][36][37][38][39].…”

A novel base-metal multifunctional catalyst for the synthesis of 2-amino-3-cyano-4H-chromenes by a multicomponent tandem oxidation process

“…The XPS spectra of W4f (Fig. 3 d) showed two peaks centered at 34.8 and 36.9 eV, related to W 6+ (W4f 7/2 , W4f 5/2 ) 74 .

Figure 3 XPS spectra of ( a ) (γ-Fe 2 O 3 -Im-Py) 2 WO 4 , ( b ) C1s, ( c ) N1s and ( d ) W4f.

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