Cathodic Activation of Titania-Fly Ash Cenospheres for Efficient Electrochemical Hydrogen Production: A Proposed Solution to Treat Fly Ash Waste

Abstract

Fly ash (FA) is a waste product generated in huge amounts by coal-fired electric and steam-generating plants. As a result, the use of FA alone or in conjunction with other materials is an intriguing study topic worth exploring. Herein, we used FA waste in conjunction with titanium oxide (TiO2) to create (FA-TiO2) nanocomposites. For the first time, a cathodic polarization pre-treatment regime was applied to such nanocomposites to efficiently produce hydrogen from an alkaline solution. The FA-TiO2 hybrid nanocomposites were prepared by a straightforward solvothermal approach in which the FA raw material was mixed with titanium precursor in dimethyl sulfoxide (DMSO) and refluxed during a given time. The obtained FA-TiO2 hybrid nanocomposites were fully characterized using various tools and displayed a cenosphere-like shape. The synthesized materials were tested as electrocatalysts for the hydrogen evolution reaction (HER) in 0.1 M KOH solution in the dark, employing various electrochemical techniques. The as-prepared (unactivated) FA-TiO2 exhibited a considerable HER electrocatalytic activity, with an onset potential (EHER) value of −144 mV vs. RHE, a Tafel slope (−bc) value of 124 mV dec−1 and an exchange current density (jo) of ~0.07 mA cm−2. The FA-TiO2′s HER catalytic performance was significantly enhanced upon cathodic activation (24 h of chronoamperometry measurements performed at a high cathodic potential of −1.0 V vs. RHE). The cathodically activated FA-TiO2 recorded HER electrochemical kinetic parameters of EHER = −28 mV, −bc = 115 mV dec−1, jo = 0.65 mA cm−2, and an overpotential η10 = 125 mV to yield a current density of 10 mA cm−2. Such parameters were comparable to those measured here for the commercial Pt/C under the same experimental conditions (EHER = −10 mV, −bc = 113 mV dec−1, jo = 0.88 mA cm−2, η10 = 110 mV), as well as to the most active electrocatalysts for H2 generation from aqueous alkaline electrolytes.

Status of fly ash-derived sustainable nanomaterials for batteries and supercapacitors

“…1 However, the original CFA's low activity precludes its direct applicability in energy storage. 132 CFA's structural modification, particle size refinement, and site activation were all accomplished using alkaline wet ball-milling, which etches the CFA surface, resulting in an increase in the pore structure. Furthermore, highly active sites like Fe 2 O 3 and TiO 2 are better exposed, which aids in the electrocatalytic activity by adsorbing and fixing the free polysulfide (LiPSs) (metal-S bonds and O–Li bonds are produced between modified CFA and LiPSs, weakening the Li–S bonds during cycling), resulting in shuttle-effect inhibition.…”

Fly‐Ash Cenosphere as Non‐Porous Ag‐Nanoparticle Support for Epoxidation of Styrene

“…Cenosphere, as the part of fly ash is seemed to be advantageous material due to low cost, high strength, lightness, chemical inertness, low bulk density and high thermal resistance. [28][29][30][31][32][33][34] Several methods of fly ash utilization have been proposed. [35] Inspiring results have been achieved with application of modified cenosphere in the esterification, [34] CO 2 methanation, [36] photocatalytic degradation of organic pollutants, [37] dry reforming of methane, synthesis of ethyl propionate [39] and hydrogen formation.…”

“…[28][29][30][31][32][33][34] Several methods of fly ash utilization have been proposed. [35] Inspiring results have been achieved with application of modified cenosphere in the esterification, [34] CO 2 methanation, [36] photocatalytic degradation of organic pollutants, [37] dry reforming of methane, synthesis of ethyl propionate [39] and hydrogen formation. [40] In this perspective, the development of new Ag NP catalysts supported on fly ash cenosphere looks promising.…”

“…Power stations around the world produce a huge amount of fly ash during the combustion of coal fuel, and this waste also requires proper handling. Cenosphere, as the part of fly ash is seemed to be advantageous material due to low cost, high strength, lightness, chemical inertness, low bulk density and high thermal resistance [28–34] . Several methods of fly ash utilization have been proposed [35] .…”