Organic-inorganic hybrid mixed-valent bisphosphonate-polyoxovanadates composites with activated carbon for energy storage applications

Abstract

In this book, we discuss the investigation of two different bisphosphonate-functionalized polyoxovanadate compounds for use in electrochemical energy storage applications. The compounds are (NH<inf>4</inf>)<inf>4</inf>[H<inf>6</inf>(VIVO<inf>2</inf>)(V<inf>V</inf>2O<inf>5</inf>)<inf>2</inf>O<inf>3</inf>P-C(O)(CH<inf>2-2-</inf>C<inf>5</inf>NH<inf>4</inf>)-PO<inf>3</inf><inf>2</inf>].9H<inf>2</inf>O (m), and (NH<inf>4</inf>)<inf>4</inf>[H<inf>6</inf>(VIVO<inf>2</inf>)(VV<inf>2</inf>O<inf>5</inf>)<inf>2</inf>O<inf>3</inf>P-C(O)(CH<inf>2-3-</inf>C<inf>5</inf>NH<inf>4</inf>)-PO<inf>3</inf><inf>2</inf>]. 8H<inf>2</inf>O (n). They have a mixed-valent oxovanadate polyanionic assembly that has two different pyridyl functional groups present on the organic bisphosphonate ligand. Several techniques have been used to characterize composites made from these compounds with activated carbon, including Fourier transform infrared spectroscopy, P-XRD, FESEM, EDX, and surface adsorption-desorption tests. The electrochemical performance of acidic electrolytic solutions containing 0.1 M H2SO4, AC-m, and AC-n electrode materials was investigated. Although the compounds are isotypic mixed-valence polyoxovanadate structures, their electrical behavior varies based on the position of the pyridyl group. AC-n was reported to have the most prominent specific capacitance of 313 F g-1 at a current density of 1 A g-1 in a voltage window of 0-1 V, with exceptional energy and power densities of 43.56 Wh kg-1 and 1999.72 W kg-1, respectively. At the same time, AC-m exhibited a specific capacitance of 212 F g-1 and a specific energy of 29.45 Wh kg-1. By lighting up different LED lights with only 42 mg of carbon clothcoated sample, the composite AC-n electrode displayed exceptional specific power. A further benefit of AC-n nanohybrids is their ability to retain electrochemical performance over time, which suggests long-term stability. © 2024 Nova Science Publishers, Inc. All rights reserved.