Atomically mixed Fe-group nanoalloys: catalyst design for the selective electrooxidation of ethylene glycol to oxalic acid

Abstract

We demonstrate electric power generation via the electrooxidation of ethylene glycol (EG) on a series of Fe-group nanoalloy (NA) catalysts in alkaline media. A series of Fe-group binary NA catalysts supported on carbon (FeCo/C, FeNi/C, and CoNi/C) and monometallic analogues (Fe/C, Co/C, and Ni/C) were synthesized. Catalytic activities and product distributions on the prepared Fe-group NA catalysts in the EG electrooxidation were investigated by cyclic voltammetry and chronoamperometry, and compared with those of the previously reported FeCoNi/C, which clarified the contributory factors of the metal components for the EG electrooxidation activity, C2 product selectivity, and catalyst durability. The Co-containing catalysts, such as Co/C, FeCo/C, and FeCoNi/C, exhibit relatively high catalytic activities for EG electrooxidation, whereas the catalytic performances of Ni-containing catalysts are relatively low. However, we found that the inclusion of Ni is a requisite for the prevention of rapid degradation due to surface modification of the catalyst. Notably, FeCoNi/C shows the highest selectivity for oxalic acid production without CO2 generation at 0.4 V vs. the reversible hydrogen electrode (RHE), resulting from the synergetic contribution of all of the component elements. Finally, we performed power generation using the direct EG alkaline fuel cell in the presence of the Fe-group catalysts. The power density obtained on each catalyst directly reflected the catalytic performances elucidated in the electrochemical experiments for the corresponding catalyst. The catalytic roles and alloying effects disclosed herein provide information on the design of highly efficient electrocatalysts containing Fe-group metals.

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.…”

“…[29] C-C bond dissociation leads to the generation of C 1 compounds and lowers the catalyst's selectivity. GC (HOCH 2 -CO 2 H) is generated by the 4-electron oxidation of EG, affording OX by a further 4-electron oxidation.…”

“…However, the synthetic methods for the preparation of Fe‐group NAs have not been fully developed. Then, we proposed a novel method to synthesize homogeneously mixed Fe‐group NA catalysts via a two‐step synthesis method and successfully synthesized the following series of Fe‐group bimetallic and ternary NAs supported on active carbon: FeCo/C, FeNi/C, NiCo/C, and FeCoNi/C 29,30. In the first step,31 mixed‐oxide 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 = Fe, Co, and/or Ni; OAc = CH 3 ) in the presence of a carbon support, followed by washing with a mixed solution of acetone and water in air.…”

Hydrogenation of oxalic acid using light-assisted water electrolysis for the production of an alcoholic compound

“…Efficient utilization of biomass resources derived from atmospheric CO 2 could be a useful strategy to curb global warming by suppressing the consumption of fossil resources as a raw material. [1][2][3][4] Recently, bio-alcohols, such as ethanol 5 and ethylene glycol, 6 have been commercialized and utilized as a fuel 7 and feedstock. 8 However, carbon resources included in biomass are not efficiently converted into alcohols, i.e.…”

“…However, severe reaction conditions are required for the catalytic hydrogenation of organic acids, i.e. high pressure (2)(3)(4)(5)(6) and temperature (100-380°C) 15 with the use of H 2 gas. The other drawback of the organic hydrogenation process is the utilization of highly reactive metal hydrides derived from fossil fuels as a hydrogen source, e.g., LiAlH 4 , 16 (BH 3 ) 2 17,18 and HSiEt 3 , 19 to activate highly stable carboxyl groups due to their low electrophilicty 20 in organic solvents, resulting in the formation of large amounts of waste.…”