CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media

Abstract

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO 2 -free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO 2 , produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C 2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO 2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system. T he consumption of finite fossil fuel energy resources has inadvertently increased the CO 2 concentration in the atmosphere, and increased concerns regarding climate issues due to CO 2 emissions have spurred the development of alternative and sustainable energy cycle systems 1,2 . This research has recently expanded to energy conversion applications via the development of fuel cells (FCs) that utilise fuels such as hydrogen or alcohol with high conversion efficiency 3 . Hydrogen, which yields water as the product of its oxidation, is regarded as an environmentally feasible fuel. However, industrial hydrogen is mainly produced by fossil fuel reforming 4 , resulting in the release of large quantities of CO 2 . The use of alcohols as alternative fuels is also anticipated due to their ability to be directly used for power generation without reforming and their high energy density. For example, the volumetric energy densities of ethanol, methanol and ethylene glycol (EG) (6.34, 4.82 5 and 5.9 kW h?L 21 6 , respectively) are higher than that of gaseous hydrogen (0.53 kWh?L 21 at 20 MPa) 5 . Among alcohols, EG is of particular interest because it has a high boiling point (197.3uC), low vapour pressure (8 Pa at 20uC) and lower toxicity 6 , essential characteristics for facilitating fuel distribution 7. EG can be produced from biomass-derived resources, e.g., cellulose, and is thus considered a promising environmentally friendly alternative fuel 8,9 . Therefore, an effective EG electrooxidation catalyst is of great interest and has been the subject of intensive study in recent decades [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . Pt-based materials are the major group of anodic electrode catalysts in direct-EG FCs. However, the precious metal dependence of these materials is a major impediment to the commercialisation of such energy-generating devices from a cost perspective 29 . EG is oxidised to several products via multiple electron oxidations (Fig. 1), with ultimate production of CO 2 , a 10-electron oxid...

CO2-free electric power circulation via direct charge and discharge using the glycolic acid/oxalic acid redox couple

“…20 Renewing alcoholic compounds by direct electroreduction of OX is another challenge, which enables highly efficient electric power circulation. Recently, we have reported power generation by the partial electrooxidation of ethylene glycol, which is easily handled, to oxalic acid (HOOC-COOH, OX) without CO 2 emission.…”

Iron-based Nanomaterials in the Catalysis

“…An Fe group ternary nanoalloy FeCoNi (NA) catalyst (its synthesis see Fig. 3) enabled selective electrocatalysis towards CO 2 -free power generation from highly deliverable ethylene glycol (EG) [73]. This FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C 2 products and to oxalic acid, i.e., 99% and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO 2 generation.…”

Experimental and Quantum Chemical Approaches to Develop Highly Selective Nanocatalysts for CO2‐free Power Circulation

“…[29,30] In the first step, [31] mixedoxide precursors were synthesized by precipitating small metallic pieces with diameters of less than 1 nm by adding NaBH 4 to a triethylene glycol solution containing divalent metal complexes, i.e., M II (OAc) 2 (M 5 Fe, Co, and/or Ni; OAc 5 CH 3 CO -2 ) in the presence of a carbon support, followed by washing with a mixed solution of acetone and water in air. The NA catalysts were then obtained by reducing the precursors with hydrogen at 500-8008C in the second step, as shown in Figure 4.…”