Effective ethanol-to-CO_(2) electrocatalysis at iridium-bismuth oxide featuring the impressive negative shifting of the working potential

Since low overpotential for the anodic ethanol oxidation reaction(EOR)can favor the higher output voltage and power of direct ethanol fuel cells(DEFCs),it is critical to design new EOR catalysts with efficient ethanol-to-CO_(2)activity at low applied potentials.Thereby,carbon-supported Ir-Bi_(2)O_(3)(Ir-Bi_(2)O_(3)/C)catalysts with highly dispersive bismuth oxide on the iridium surface are designed and prepared,which can merit splitting the ethanol C–C bond and promoting the oxidation of C1 intermediates at the bifunctional interfaces.The as-obtained Ir-Bi2O3/C catalysts show superior EOR mass activity of up to ca.2250 m A mgIr-1.Moreover,they exhibit the record lowest onset oxidation potentials(0.17–0.22 V vs.RHE)and the peak potential(ca.0.58 V vs.RHE),being 130–300 m V lower than the previous landmark noble metallic catalysts.Furthermore,an apparent C1 pathway faraday efficiency(FEC1)of 28%±5.9%at 0.5 V vs.RHE can be obtained at Ir-Bi_(2)O_(3)/C.This work might provide new insights into the new anodic EOR catalysts for increasing the power of DEFCs.

Unraveling the role of iron on Ni-Fe alloy nanoparticles during the electrocatalytic ethanol-to-acetate process

The anodic electrooxidation of ethanol to value-added acetate is an excellent example of replacing the oxygen evolution reaction to promote the cathodic hydrogen evolution reaction and save energy.Herein,we present a colloidal strategy to produce Ni-Fe bimetallic alloy nanoparticles(NPs)as efficient electrocatalysts for the electrooxidation of ethanol in alkaline media.Ni-Fe alloy NPs deliver a current density of 100 mA·cm^(-2) in a 1.0 M KOH solution containing 1.0 M ethanol merely at 1.5 V vs.reversible hydrogen electrode(RHE),well above the performance of other electrocatalysts in a similar system.Within continuous 10 h testing at this external potential,this electrode is able to produce an average of 0.49 mmol·cm^(-2)·h^(-1) of acetate with an ethanol-to-acetate Faradaic efficiency of 80%.A series of spectroscopy techniques are used to probe the electrocatalytic process and analyze the electrolyte.Additionally,density functional theory(DFT)calculations demonstrate that the iron in the alloy NPs significantly enhances the electroconductivity and electron transfer,shifts the rate-limiting step,and lowers the energy barrier during the ethanol-to-acetate reaction pathway.

Boosting CO_(2) electroreduction to formate via bismuth oxide clusters

Supported metal(oxide)clusters,with both rich surface sites and high atom utilization efficiency,have shown improved activity and selectivity for many catalytic reactions over nanoparticle and single atom catalysts.Yet,the role of cluster catalysts has been rarely reported in CO_(2)electroreduction reaction(CO_(2)RR),which is a promising route for converting CO_(2)to liquid fuels like formic acid with renewable electricity.Here we develop a bismuth oxide(BiOn)cluster catalyst for highly efficient CO_(2)RR to formate.The BiOn cluster catalyst exhibits excellent activity,selectivity,and stability towards formate production,with a formate Faradaic efficiency of over 90%at a current density up to 500 mA·cm^(−2)in an alkaline membrane electrode assembly electrolyzer,corresponding to a mass activity as high as 3,750 A·gBi−1.The electrolyzer with the BiOn cluster catalyst delivers a remarkable formate production rate of 0.56 mmol·min−1 at a high single-pass CO_(2)conversion of 44%.Density functional theory calculations indicate that Bi4O_(3)cluster is more favorable for stabilizing the HCOO^(*)intermediate than Bi(001)surface and single site BiC_(4)motif,rationalizing the improved formate production over the BiOn cluster catalyst.This work highlights the great importance of cluster catalysts in activity and selectivity control in electrocatalytic CO_(2)conversion.

Unraveling and tuning the linear correlation between CH_(4) and C_(2) production rates in CO_(2) electroreduction

Although many catalysts have been reported for the CO_(2)electroreduction to C_(1)or C_(2)chemicals,the insufficient understanding of fundamental correlations among different products still hinders the development of universal catalyst design strategies.Herein,we first discover that the surface*CO coverage is stable over a wide potential range and reveal a linear correlation between the partial current densities of CH_(4)and C_(2)products in this potential range,also supported by the theoretical kinetic analysis.Based on the mechanism that*CHO is the common intermediate in the formation of both CH_(4)(*CHO→CH4)and C_(1)(*CHO+*CO→C_(2)),we then unravel that this linear correlation is universal and the slope can be varied by tuning the surface*H or*CO coverage to promote the selectivity of CH_(4)or C_(2)products,respectively.As proofs-of-concept,using carbon-coated Cu particles,the surface*H coverage can be increased to enhance CH_(4)production,presenting a high CO_(2)-to-CH_(4)Faradaic efficiency(FE_(CH_(4))~52%)and an outstanding CH_(4)partial current density of-337 m A cm;.On the other hand,using an Agdoped Cu catalyst,the CO_(2)RR selectivity is switched to the C_(2)pathway,with a substantially promoted FE;of 79%and a high partial current density of-421 m A cm;.Our discovery of tuning intermediate coverages suggests a powerful catalyst design strategy for different CO_(2)electroreduction pathways.