Abstract
The electrocatalytic reduction of CO2 on Au-Pt bimetallic catalysts with different compositions was evaluated, offering a platform for uncovering the correlation between the catalytic activity and the surface composition of bimetallic electrocatalysts. The Au-Pt alloy films were synthesized by a magnetron sputtering co-deposition technique with tunable composition. It was found that the syngas ratio (CO:H2) on the Au-Pt films is able to be tuned by systematically controlling the binary composition. This tunable catalytic selectivity is attributed to the variation of binding strength of COOH and CO intermediates, influenced by the surface electronic structure (d-band center energy) which is linked to the surface composition of the bimetallic films. Notably, a gradual shift of the d-band center away from the Fermi level was observed with increasing Au content, which correspondingly reduces the binding strength of the COOH and CO intermediates, leading to the distinct catalytic activity for the reduction of CO2 on the compositionally variant Au-Pt bimetallic films. In addition, the formation of formic acid in the bimetallic systems at reduced overpotentials and higher yield indicates that synergistic effects can facilitate reaction pathways for products that are not accessible with the individual components.
Highlights
Converting CO2 electrochemically into fuels and valuable chemicals has great potential for the utilization of captured CO2 [1,2,3,4,5,6]
The shift of the d-band center away from the Fermi level with increasing Au composition is found from Density functional theory (DFT) calculation (Fig. S8). This exploration of the electronic effect on the catalytic activity for CO2 reduction in the bimetallic system suggests that the binding strength for intermediates on Au-Pt bimetallic films likely follows the scaling relation, which is in agreement with the previous DFT simulation work for Au-Pd alloy surfaces [25]
Au-Pt bimetallic thin films with tunable compositions were prepared with a uniform morphology, offering a platform for understanding the electronic effect on the catalytic activity for CO2 reduction in a bimetallic system
Summary
Converting CO2 electrochemically into fuels and valuable chemicals has great potential for the utilization of captured CO2 [1,2,3,4,5,6]. We present the first exploration of the electrocatalytic reduction of CO2 on Au-Pt bimetallic thin films with controllable compositions and planar morphology These bimetallic planar films provide an ideal platform for investigating the electronic and synergistic effects on the binding strength of intermediates and the formation of final products by tuning the composition of bimetallic catalysts while keeping the surface morphology consistent. A systematic experimental and theoretical investigation elaborates the mechanism of the effect of binary catalyst composition on the catalytic activity and selectivity of CO2 reduction, revealing that major products formation (H2 and CO) closely follows the surface compositional change, while the formation of HCOOH on Au-Pt films was found to occur at lower overpotentials and with significantly improved amounts. The surface composition and bimetallic synergy of two metals both contribute to the overall CO2 reduction performance of Au-Pt electrocatalysts
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