Ultrasmall Au nanocatalysts supported on nitrided carbon for electrocatalytic CO₂ reduction: the role of the carbon support in high selectivity

Abstract

Au is one of the most promising electrocatalysts to convert CO2 into CO in an aqueous-phase electrochemical reduction. However, ultrasmall Au nanocatalysts (AuNCs, <2 nm) have proven to be favorable for water reduction over CO2, although they possess a large surface-to-volume ratio and potentially are ideal for CO2 reduction. We herein report that ultrasmall AuNCs (1.9 ± 0.3 nm) supported on nitrided carbon are remarkably active and selective for CO2 reduction. The mass activity for CO of AuNCs reaches 967 A g-1 with a faradaic efficiency for CO of ∼83% at -0.73 V (vs. reversible hydrogen electrode) that is an order of magnitude more active than the state-of-the-art results. The high activity is endowed by the large surface area per unit weight and the high selectivity of ultrasmall AuNCs for CO2 reduction originates from the cooperative effect of Au and the nitrided carbon support where the surface N sites act as Lewis bases to increase the surface charge density of AuNCs and enhance the localized concentration of CO2 nearby catalytically active Au sites. We show that our results can be applied to other pre-synthesized Au catalysts to largely improve their selectivity for CO2 reduction by 50%. Our method is expected to illustrate a general guideline to effectively lower the cost of Au catalysts per unit weight of the product while maintaining its high selectivity for CO2 reduction.

Carbon‐based metal‐free catalysts for electrochemical CO2 reduction: Activity, selectivity, and stability

“…Jin et al 108 synthesized N‐doped carbon‐supported ultra‐small gold (AuNCs < 2 nm). They found that their catalyst was selective towards CO with a maximum FE of 83% at –0.73 V RHE .…”

Enhancing CO2 Electroreduction with Au/Pyridine/Carbon Nanotubes Hybrid Structures

“…To further understand the proposed reaction mechanism, we conducted DFT calculations with Au/Py/CNT and Au/CNT to calculate the free energies of the following reaction mechanistic steps [Eqs. (1)–], where * denotes an adsorption site and e − is an electron. …”

“…[7] Currently,t here are two fundamentally different approaches to the development of such materials: (i)fine-tuning of the electronic properties of Au surface atoms by supports [8] or surface ligands [9] and (ii)increasing the concentration of CO 2 on support surfaces by sorbents or cocatalysts. [10] However,t he improvement of catalysta ctivity usually comesa tt he expense of decreasing its selectivity with the introduction of those additives. Therefore, industrial application of CO 2 electroreduction to CO is still challenged by the lack of efficient catalysts with highactivity,s electivity,and stability.…”

Manipulating Au−CeO2 Interfacial Structure Toward Ultrahigh Mass Activity and Selectivity for CO2 Reduction

“…Typically, decreasing the particle size is an effective approach since only the surface atoms are active to CO 2 RR. [11] Density functional theory (DFT) calculations also indicated that Au particle size has a significant influence on the affinity of the intermediate compounds (e. g., *COOH, *CO), [12] where CO 2 reduction rate with smaller Au particles is reported higher than that of the extended surface. [5b] Unfortunately, a similar trend was seen for the competing hydrogen evolution reaction (HER).…”