Regulating Morphological Features of Nickel Single‐Atom Catalysts for Selective and Enhanced Electroreduction of CO₂

Abstract

Single‐atom catalysts (SACs) are of interest for chemical transformations of significant energy and environmental relevance because of the envisioned efficient use of active sites and the flexibility in tuning their coordination environment. Future advancement in this vein hinges upon the ability to further increase the number and accessibility of active sites in addition to fine‐tuning their chemical environment. In this work, a Ni SAC is reported with a unique hierarchical hollow structure (Ni/HH) that allows increased accessibility of the active sites. The successful obtainment of such a uniquely structured catalyst was enabled by the judiciously chosen solvent mixtures for the preparation of the precursor whose hierarchical feature is maintained during the subsequent pyrolysis and etching of the pyrolysis product. Comparative catalytic and mechanistic studies with reference to three closely related but more compact Ni SACs established the superior performance of Ni/HH for selective electroreduction of CO2 to CO. Experimental analyses by in situ attenuated total reflection surface‐enhanced infrared spectroscopy reveal that it is the facilitated formation of the *COOH intermediate in the rate‐determining step that leads to the enhanced reaction kinetics and the overall catalytic performance.

Facile synthesis of single‐nickel‐atomic dispersed mesoporous carbon nanosheets with controllable nitrogen doping for efficient electrochemical CO2 reduction

“…And the feature peaks at 1440 cm −1 belong to the symmetric stretch of COO − . The intermediates in the process of electrocatalytic reduction of CO 2 to CO are generally COOH and COO − , [59] therefore the presence of these characteristic peaks proves the stable existence of the catalytic intermediate on Ni@NMCN4. This is also the reason why the Ni@NMCN4 catalyst can efficiently electrocatalystically reduce CO 2 , which is attributed to the atomic level dispersion of Ni and the successful coordination of Ni−N 4 .…”

Customizing pyridinic nitrogen coordination in Ni–N–C for electrocatalytic CO2 reduction towards CO

“…To probe into the CO 2 RR process of Ni-N x -C, in-situ ATR-FTIR spectroscopy was used to analyze the intermediates and products at different CO 2 RR potentials (figure 4). The peaks at 1268 cm −1 , 1325 cm −1 , 1403 cm −1 and 1568 cm −1 corresponds to the OH deformation, C-O stretch, symmetric stretch, asymmetric stretch of * COOH, severally [43,44], universally considered to be the pivotal intermedium of CO 2 electroreduction to CO. To be noted, the * CO intermediate peak is hardly detected mainly associated with its facile detachment. With the voltage rising from the open-circuit state to −0.68 V vs. RHE, the peak area of * COOH increased gradually and keep unchanging with further varying to −1.38 V (vs. RHE), as a result of the fact that the active sites are nearly covered with reactants and intermedium.…”

Advances and challenges in the electrochemical reduction of carbon dioxide

“…There are some reports on cobalt-, iron-, zirconium-, bismuth- and nickel-based MOFs-derived catalysts. A series of MOFs with different morphologies (abbreviated as Ni-MOF-525) with zirconia clusters as nodes and nickel porphyrin complexes as bridging ligands were synthesized by Zheng et al 259 Ni SACs in an H-cell possessed an urchin-like hierarchical structure with internal voids, with rapid and highly selective electroreduction of CO 2 to CO (FE CO = 98%) even at a current density as high as 200 mA cm −2 . Fe-N-C catalyst derived from Fe-MOF was found to exhibit high Faraday efficiency (86.8%) for CO products at an overpotential of 496 mV and excellent long-term stability due to the good inheritance of the Fe-MOF precursor.…”