Porous PdWM (M = Nb, Mo and Ta) Trimetallene for High C1 Selectivity in Alkaline Ethanol Oxidation Reaction

Abstract

Direct ethanol fuel cells are among the most efficient and environmentally friendly energy-conversion devices and have been widely focused. The ethanol oxidation reaction (EOR) is a multielectron process with slow kinetics. The large amount of by-product generated by incomplete oxidation greatly reduces the efficiency of energy conversion through the EOR. In this study, a novel type of trimetallene called porous PdWM (M = Nb, Mo and Ta) is synthesized by a facile method. The mass activity (15.6 A mg Pd −1 ) and C1 selectivity (55.5%) of Pd 50 W 27 Nb 23 /C trimetallene, obtained after optimizing the compositions and proportions of porous PdWM, outperform those of commercial Pt/C (1.3 A mg Pt −1 , 5.9%), Pd/C (5.0 A mg Pd −1 , 7.2%), and Pd 97 W 3 /C bimetallene (9.5 A mg Pd −1 , 14.1%). The mechanism by which Pd 50 W 27 Nb 23 /C enhances the EOR performance is evaluated by in situ Fourier transform infrared spectroscopy and density functional theory calculations. It is found that W and Nb enhance the adsorption of CH 3 CH 2 OH and oxophilic high-valence Nb accelerates the subsequent oxidation of CO and -CH x species. Moreover, Nb promotes the cleavage of C-C bonds and increases the C1 selectivity. Pd 60 W 28 Mo 12 /C and Pd 64 W 27 Ta 9 /C trimetallene synthesized by the same method also exhibit excellent EOR performance.

A rhodium–cobalt alloy bimetallene towards liquid C1 molecule electrooxidation in alkaline media

“…[14][15][16][17][18][19][20] Recently, metallene, a class of two-dimensional (2D) graphene-like metallic nanosheets, have emerged as the star electrocatalysts because of their abundant unsaturated atoms with high activity and ultrahigh surface area. [21][22][23][24][25][26] For example, Wang and his co-workers successfully synthesized Pd metallene with 1 nm thickness using a one-pot wet-chemical method, which exhibited excellent electroactivity for the oxygen reduction reaction, owing to optimized oxygen binding ability and the active site-rich feature. 26 Shao and his co-workers successfully synthesized iridium (Ir) metallene oxide, which is highly active for the oxygen evolution reaction because of full atom utilization and maximized surface active sites.…”

Facet-Controlled PdP Nanosheets for Ethanol Electrooxidation

“…Ethanol is a promising fuel with low toxicity, easy availability, and the ability to be oxidized at relatively low potentials and thus can be applied in energy-conversion devices, i.e., direct ethanol fuel cells. − During the complete oxidation of ethanol to CO 2 , 12 electrons are delivered per molecule (eq ), indicating a higher energy density than methanol: However, in practice, the ethanol oxidation reaction may follow an incomplete oxidation pathway, which drastically cuts the energy density and is kinetically slow (eq ): Therefore, a variety of electrocatalysts have been designed to solve the problems of low Faraday efficiency and poor selectivity for ethanol oxidation reaction (EOR). − …”

Multiple strategies of porous tetrametallene for efficient ethanol electrooxidation

“…31,32 In addition, the introduction of components (e.g., Rh and Nb) that are favorable to the cleavage of the C-C bond of ethanol allows ethanol to split easily into C1 intermediates (i.e., CO ad and -CH x species) on the surface, forming selective sites for CO 2 , thereby improving the C1 selectivity in the EOR. [33][34][35] However, a single strategy has limited modulation of EOR performance and it is difficult to reconcile superior activity, stability and C1 selectivity. To our knowledge, there are no catalysts combining multiple strategies to improve C1 selectivity, activity and excellent stability.…”