The Hallmarks of Copper Single Atom Catalysts in Direct Alcohol Fuel Cells and Electrochemical CO₂ Fixation

Abstract

Single‐atom catalysts (SACs) are highly enviable to exploit the utmost utilization of metallic catalysts; their efficiency by utilizing nearly all atoms to often exhibit high catalytic performances. To architect the isolated single atom on an ideal solid support with strong coordination has remained a crucial trial. Herein, graphene functionalized with nitrile groups (cyanographene) as an ideal support to immobilize isolated copper atoms G(CN)‐Cu with strong coordination is reported. The precisely designed mixed‐valence single atom copper (G(CN)‐Cu) catalysts deliver exceptional conversions for electrochemical methanol oxidation (MOR) and CO2 reduction (CO2RR) targeting a “closed carbon cycle.” An onset of MOR and CO2RR are obtained to be ≈0.4 V and ≈−0.7 versus Ag/AgCl, respectively, with single active sites located in an unsaturated coordination environment, it being the most active Cu sites for both studied reactions. Moreover, G(CN)‐Cu exhibited significantly lower resistivity and higher current density toward MOR and CO2RR than observed for reference catalysts.

Copper single-atoms embedded in 2D graphitic carbon nitride for the CO2 reduction

“…This could be attributed to the presence of copper oxide nanoparticles. It should be highlighted that the results obtained with our Cu-GCN system are in line with those reported in the literature for similar systems 44,56 , obtaining CO (ca. 30% FE) as the main CO 2 reduction product, together with a variety of different products as CH 4 , CH 3 OH, and several C2 species with a very low FE (<4%).…”

“…However, the mixture of different liquids and gas products requires a further separation step. The catalytic activity, in terms of current density, of our Cu-GCN (14 mA/mg cat ) system is also comparable with the copper-doped cyanographene (10−20 mA/mg) reported by Pieta et al 56 .…”

“…2), suggesting the presence of both Cu 2+ and Cu + , due to different Cu−N coordination arrangements. The presence of two different valence states has been already reported for Cu single atoms embedded in carbon nitride or N-doped graphene-related materials 6,53,56 . Fig.…”

Elucidating the Role of Single-Atom Pd for Electrocatalytic Hydrodechlorination

“…54,72 Similarly, single-atom Cu for electrochemical CO 2 reduction exhibits superb resistance to methanol poisoning, which is attributed to its weaker binding, in comparison to Cu nanoparticles. 73 Such decreased binding affinities have been attributed to the adsorbate-induced structural relaxation of SACs, wherein the unsaturated coordination environment enables the distortion of the SAC structure to affect the desorption of the intermediate. 28,31,32 Combining these previous findings and our experimental results, we propose that the superior catalytic stability of Pd 1 /rGO over Pd nano / rGO for 4-CP hydrodechlorination results from its single-atom nature.…”

Factors Influencing the Performance of Copper-Bearing Catalysts in the CO2 Reduction System

“…At present, due to the specific binding energy of the *CO intermediate, copper is the only transition metal element that can effectively produce C 2 + products. − However, due to the high overpotential and poor selectivity of Cu in the CO 2 RR, improving the catalytic performance of Cu has always been a hot topic. It is well known that the coordination structure and electronic state of the active site can regulate the catalytic performance of the catalyst. ,, The main reason is that the reaction pathway of the CO 2 RR is different, thus generating different products.…”