Synergistic Enhancement of Electrocatalytic CO₂ Reduction with Gold Nanoparticles Embedded in Functional Graphene Nanoribbon Composite Electrodes

Abstract

Regulating the complex environment accounting for the stability, selectivity, and activity of catalytic metal nanoparticle interfaces represents a challenge to heterogeneous catalyst design. Here we demonstrate the intrinsic performance enhancement of a composite material composed of gold nanoparticles (AuNPs) embedded in a bottom-up synthesized graphene nanoribbon (GNR) matrix for the electrocatalytic reduction of CO. Electrochemical studies reveal that the structural and electronic properties of the GNR composite matrix increase the AuNP electrochemically active surface area (ECSA), lower the requisite CO reduction overpotential by hundreds of millivolts (catalytic onset > -0.2 V versus reversible hydrogen electrode (RHE)), increase the Faraday efficiency (>90%), markedly improve stability (catalytic performance sustained over >24 h), and increase the total catalytic output (>100-fold improvement over traditional amorphous carbon AuNP supports). The inherent structural and electronic tunability of bottom-up synthesized GNR-AuNP composites affords an unrivaled degree of control over the catalytic environment, providing a means for such profound effects as shifting the rate-determining step in the electrocatalytic reduction of CO to CO, and thereby altering the electrocatalytic mechanism at the nanoparticle surface.

Tuning Gold Nanoparticles with Chelating Ligands for Highly Efficient Electrocatalytic CO2 Reduction

“…[23][24][25][26][27][28][29][30][31][32][33][34] Metal NPs often possess surfactants with long alkyl chains to stabilize the surfaces.H owever,t hese surfactants can block the catalytically active sites of metal NPs and lower the catalytic activity. These catalysts also show excellent stability without deactivation (< 5% productivity loss) within 72 hours of electrolysis.D FT calculation results further confirm the chelation effect in stabilizing molecule/NP interface and tailoring catalytic activity.T his general approachi s thus anticipated to be complementary to current NP catalyst design approaches.…”

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Capped chelating organic molecules are presented as ad esign principle for tuning heterogeneous nanoparticles for electrochemical catalysis.G old nanoparticles (AuNPs) functionalized with achelating tetradentate porphyrin ligand show a1 10-fold enhancement compared to the oleylamine-coated AuNP in current density for electrochemical reduction of CO 2 to CO in water at an overpotential of 340 mV with Faradaic efficiencies (FEs) of 93 %. [25,28,31,33] In this context, stabilization of metal surfaces while maintaining catalytic active sites through rational molecular design of surface capping ligands of NPs is highly desired. Among the many electrocatalysts for CO 2 RR, metal nanoparticles (NPs) have been extensively studied due to their high conductivity,large surface area, and high stability under reductive potentials.

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“…Among the many electrocatalysts for CO 2 RR, metal nanoparticles (NPs) have been extensively studied due to their high conductivity,large surface area, and high stability under reductive potentials. [27,33] Thel igand exchange step for preparing porphyrin-functionalized Au NPs (P1-AuNP) was carried out by soaking OAm-AuNP in 50 mm dichloromethane solutions of P1 for 12 h(see the Supporting Information). [26-28, 33, 35] Furthermore,t he mono-dentate nature of these surfactants can result in ligand detachment under the electrochemical operation, causing particle aggregation and consequent activity decay.…”

“…[23][24][25][26][27][28][29][30][31][32][33][34] Metal NPs often possess surfactants with long alkyl chains to stabilize the surfaces.H owever,t hese surfactants can block the catalytically active sites of metal NPs and lower the catalytic activity. [28,33] Thesuccessful attachment of P1 to the surface of Au NPs was first identified by UV/Vis spectroscopy (Figure 1a). [25,28,31,33] In this context, stabilization of metal surfaces while maintaining catalytic active sites through rational molecular design of surface capping ligands of NPs is highly desired.…”

The Effect of Electrodeposition Parameters and Morphology on the Performance of Au Nanostructures for the Detection of As (III)

“…Pb UPD is an effective technique to probe the surface crystallographic structures of gold materials and has been extensively studied on polycrystalline and single crystalline gold materials. [48][49][50] Since the lead UPD process is stucture sensitive, the potentials of the lead deposition and stripping peaks are used to assist with identification of the relative energy of facets on the surface of the gold spikes in contact with solution. 40,51 Figure S4 (see Supporting Information) depicts the cyclic voltammograms of the gold spikes in an alkaline solution of lead (II) nitrate with a broad potential window.…”