The molten-salt assisted self-assembly (MASA) process is applicable to fabricate high quality mesoporous metal lithiate thin films that exhibit excellent performance as electrocatalysts for water oxidation.
the literature, the synthesis of mesoporous metal oxides and metal lithiates has always been a challenge. Many strategies for synthesis, including hard and soft templating methods, have been developed over the years. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The lyotropic liquid crystalline (LLC) templating method has also been employed to produce metals and metal oxides with the help of a reducing agent or electrochemical methods. [21][22][23][24][25] Unfortunately, the many existing metal ion precursors are not appropriate for use in soft and hard templating. There are some successful examples of the synthesis of mesoporous metal oxides by using alkoxy precursors. [26][27][28][29][30] However, most metal precursors are common ion salts, such as metal chlorides, nitrates, sulfates, and acetates, that need high temperatures to undergo hydrolysis and condensation reactions to form their oxides. Even if one can incorporate the salts into mesophases, in the next step, in going from salt precursors to oxides, the salt species shrink by 70-90%, which causes a collapse of the meso-order in soft templating processes or a nonuniform coating in the hardtemplating cases. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] There are no examples of mesoporous thin films produced through hard-templating and there has been limited success with soft templating methods. In particular, the oxides that contain two or more metals are even more difficult to assemble into mesoporous materials. It is still extremely challenging to form and maintain mesostructures in most metal based materials.Although, there are some successful examples of mesoporous metal lithiates powders, using hard templating method, [15][16][17][18][19][20] the method is quite complex and generally impossible to produce thin films. Bruce and co-workers reported the first synthesis of mesoporous low temperature spinel LiCoO 2 and LiCoO 2 nanowires. [31] The synthesis of mesoporous spinel LiMn 2 O 4 has been reported by Luo et al. [32] Hwang et al. obtained the mesoporous metal lithiates by using soft templating. [33] The resulting material had a 3.8 nm pore size, 31 nm wall thickness, and 13.8 m 2 g −1 surface area. [34] . The method described can be adopted to synthesize other metal oxides and metal lithiates. The mesoporous thin films of LiCoO 2 show promising performance as water oxidation catalysts under pH 7 and 14 conditions. The electrodes, prepared using CTAN as the cosurfactant, display the lowest overpotentials in the literature among other LiCoO 2 systems, as low as 376 mV at 10 mA cm -2 and 282 mV at 1 mA cm -2 .
Mesoporous Thin Films
In article number 1701913, Ferdi Karadas, Ömer Dag, and co-workers synthesize transparent mesoporous thin films of LiCoO 2 and LiMn 2 O 4 by employing a molten salt assisted self-assembly method. A clear solution of the ingredients is coated over a subtrate that is heated at elevated temperatures to obtain the transparent mesoporous metal lithiates. The mesoporous LiCoO 2 film electrode, coated over a FTO substrate, demonstrates promising water oxidation electrocatalysis at low overpotentials.
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