Cathodic Synthesis of Birnessite-Type Layered Manganese Oxides for Electrocapacitive Catalysis

Abstract

Cathodic reduction of aqueous MnO 4− ions in the presence of various alkaline metals except for Na + ions led to the deposition of birnessite-type layered MnO 2 . The highest crystallinity was obtained when electrolyzed in a 2 mM KMnO 4 and 50 mM KCl at a constant potential of 0 V vs Ag/AgCl. The cathodic formation of MnO 2 was prevented by the presence of divalent cations, and Na + ions gave rise to an amorphous or low crystalline product. The birnessite film thus formed exhibited an excellent pseudocapacitive behavior in the as-deposited state, with a specific capacitance as high as 322 F g −1 at a scan rate of 2 mV s −1 , which is much larger than that (75 F g −1 ) of the birnessite film grown anodically. The resulting pseudocapacitive electrode functioned as an efficient catalyst toward the oxidation of L-cysteine, where the anodic overpotential was reduced by 0.15 to 0.3 V.

Materials and fabrication of electrode scaffolds for deposition of MnO2 and their true performance in supercapacitors

“…Typically, this reaction produces a birnessite-type manganese oxide (A x MnO 2 ) thin film with morphology of wrinkled thin sheets [229,230]. This cathodic deposition approach has been used to load MnO 2 on CNTs arrays grown on stainless steel mesh [142].…”

Microwave-assisted rapid synthesis of birnessite-type MnO2 nanoparticles for high performance supercapacitor applications

“…Among these forms, d-MnO 2 (also known as birnessite-type MnO 2 ) has gained special attention as an electrode material for supercapacitors because of its thin sheetlike lamellar structure stabilized by alkali ions (Na + or K + ) and crystallized water, which is similar to that of hydrated ruthenium oxide [12]. Such structure can be beneficial to facilitate the cations' intercalation/deintercalation process [13,14] Several methods have been developed to prepare various birnessite-type MnO 2 nanostructures, including hydrothermal synthesis [15][16][17], microemulsion route [18], polyol-reflux [19], oxidation reaction procedure [13,14,20], and electrodeposition [21]. Compared with these synthetic methods, microwave-assisted route is a very fast, simple, and effective method for synthesis of MnO 2 materials [22,23].…”

A novel formaldehyde sensor based on the pseudocapacitive catalysis of birnessite

“…The film preparation was carried out in an aqueous solution of 2 mM KMnO 4 with and without 50 mM KCl. The working electrode was transferred into the solution, and a constant potential of 0 V was applied for about 30 min [20]. The charge consumed for the electrolysis was fixed to 280 mC/cm 2 .…”

“…Broad peaks marked with an asterisk at 25.1°and 43.2°in 2θ are due to GC substrate. In addition to these, one diffraction peak appears at 12.2°, corresponding to a d-spacing of 0.72 nm, which can be indexed to the 001 face of birnessite-type layered MnO 2 [20]. The interlayer is occupied with hydrated K + ions to electrically balance the negative charge on MnO 2 layers.…”