Graphdiyne supported Ag-Cu tandem catalytic scheme for electrocatalytic reduction of CO2 to C2+ products.

The electrochemical CO2 reduction reaction (CO2RR) to added-value C2+ products is a worthy way to effectively reduce CO2 levels in the atmosphere. Cu nanomaterials have been proposed as efficient CO2RR catalysts for producing C2+ products; however, the difficulties in controlling their efficiency and selectivity hinder their applications. Herein, we propose a simple routine to construct a graphdiyne (GDY) supported Ag-Cu nanocluster as a C2+ product-selective electrocatalyst and optimize the composition by electrochemical performance screening. The synthesized Ag-Cu nanoclusters are uniformly distributed on the surface of GDY with particle sizes constricted to 3.7 nm due to the strong diyne-Cu interaction. Compared to Cu/GDY, Ag-Cu/GDY tandem schemes exhibited superior CO2RR to C2+ performance with a Faraday efficiency (FE) of up to 55.1% and a current density of 48.6 mA cm-2 which remain stable for more than 33 hours. Theoretical calculations show that the adsorption energy of CO is much higher on Cu (-1.066 eV) than on Ag (-0.615 eV), thus promoting the drift of *CO from Ag to Cu. Moreover, the calculations indicate that the key C-C coupling reaction of *CO with *COH is more favored on Ag-Cu/GDY than on the original Cu/GDY which contributes to the formation of C2+ products. Our findings shed light on a new strategy of combining a GDY support with a tandem catalytic scheme for developing new CO2RR catalysts with superior selectivity and activity for C2+ products.

Two birds with one stone: large catalytic areas and abundant nitrogen sites inspired by fluorine doping contributing to CO2RR activity and selectivity.

Electroreduction of CO2 based on metal-free carbon catalysts is an attractive approach for useful products. However, it remains a great chemical challenge due to its unsatisfactory activity and poor selectivity. Here, we report a successful case to greatly improve CO2-to-CO conversion on carbon black (CB) and nitrogen-doped carbon black (N-CB). By introducing fluorine, the faradaic efficiency of CO was increased from 12.8% (CB) and 50.8% (N-CB) to 93.1% (nitrogen and fluorine co-doped carbon black, N,F-CB) at -0.7 V. A partial current density of 4.19 mA cm-2 remained durable for about 23 h. The superiority of N,F-CB can be attributed to its large catalytic areas and abundant N active sites inspired by fluorine doping. Specifically, the fluorine precursor of polyvinylidene fluoride (PVDF) firstly performs as a nitrogen fixator, protecting the catalyst from more nitrogen escaping during the carbonization treatment. The number of nitrogen sites is about 4.4 times higher than it is for the N-CB. Meanwhile, PVDF as the area extender significantly improves the catalytic area; the specific surface area and the ECSA of N,F-CB are 8.7 and 6.9 times higher than that of CB. This work provides an insight into how heteroatoms can manipulate catalytic activity and selectivity through the catalytic area of carbon materials with more active sites.