Abstract
Electrocatalytic reduction of CO2 recently emerged as a viable solution in view of changing the common belief and considering carbon dioxide as a valuable reactant instead of a waste product. In this view, we herein propose the one-step synthesis of gold nanostructures of different morphologies grown on fluorine-doped tin oxide electrodes by means of pulsed-laser deposition. The resulting cathodes are able to produce syngas mixtures of different compositions at overpotentials as low as 0.31 V in CO2-presaturated aqueous media. Insights into the correlation between the structural features/morphology of the cathodes and their catalytic activity are also provided, confirming recent reports on the remarkable sensitivity toward CO production for gold electrodes exposing undercoordinated sites and facets.
Highlights
The containment of the greenhouse effect and of serious alterations to ecosystems will likely require the net reversal of the currently increasing carbon dioxide (CO2) emission trend and extensive sequestration of this gas from the atmosphere.[1,2] In this context, the conversion of CO2 in alternative fuels by electrochemical reduction represents an intriguing strategy toward the establishment of a virtuous circle,[3−9] especially if the use of an electrical grid powered by renewable sources is envisaged
We report on the pulsed-laser deposition of two different kinds of porous Au-nanostructured thin films on fluorine-doped tin oxide (FTO) electrodes and their use as cathodes for CO2 reduction in aqueous electrolytes
The nanostructured Au cathodes were deposited by means of pulsed-laser deposition (PLD) on FTO substrates covered with a thin (5 nm) Cr adhesion layer prepared by thermal evaporation
Summary
The containment of the greenhouse effect and of serious alterations to ecosystems will likely require the net reversal of the currently increasing carbon dioxide (CO2) emission trend and extensive sequestration of this gas from the atmosphere.[1,2] In this context, the conversion of CO2 in alternative fuels by electrochemical reduction represents an intriguing strategy toward the establishment of a virtuous circle,[3−9] especially if the use of an electrical grid powered by renewable sources is envisaged. Engineered Au morphologies aimed at maximizing CO selectivity have been prepared through most various synthetic strategies, including (i) oxidation/re-reduction of Au foils,[20] promoted by O2 plasma treatments,[31] (ii) electroplating onto host templates,[32] (iii) optimized electrodeposition[24] or electrocrystallization with MHz potential oscillation,[33] (iv) electron beam deposition,[25,26,34] and (v) deposition of preformed Au nanostructures on conductive electrodes.[22,35,36] In this context, straightforward one-step synthesis of porous Au structures with tunable morphology (upon appropriately changing the process parameters and not involving substrate limitations or thermal treatments) appears to be intriguing These conditions could be fulfilled by pulsed-laser deposition (PLD), a highly versatile technique for the production of nanostructured films[37] or nanoparticles[38] of virtually any material, including metals,[39] alloys,[40] semiconductor oxides,[41] and carbon.[42] Highly porous structures are typically achieved by performing laser ablation in the presence of a background gas, and the resulting morphology can be tuned by controlling the gas pressure and/or target-to-substrate distance.[41,43,44] Recently, some of us showed that PLD can be used to produce Au nanoparticles with a precise control of size and substrate coverage while reporting their integration in the nanostructured TiO2 film by single-step deposition.[39,41]. Manifold setups and technological solutions for the electrochemical syngas preparation have been reported to date.[45−49] Among them, the electrochemical generation of syngas mixtures at low overpotentials suits well in a CO2 valorization scenario, especially considering that one of the major costs in the whole Fischer−Tropsch processes is the syngas production itself (usually originating from methane or coal via steam reformation[50])
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