Enhancement of CO2 Electroreduction by Ni Sacs Embedded in Chalcogenide-Doped Carbon Nanofibers - An Electrochemical Study
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-07-11 |
| Journal | ECS Meeting Abstracts |
| Authors | Varad A. Modak, KueiāHsien Chen, Osama Nasr, Mengstu Etay Ashebir, Mohammad Qorbani |
Abstract
Section titled āAbstractāThe process of electrocatalytically reducing carbon dioxide (COā) into valuable fuels and chemicals has gained significant focus as an environmentally-friendly strategy to mitigate the ongoing climate crisis, while still maintaining a net-zero carbon cycle. The electrochemical conversion of COā into chemical feedstocks like carbon monoxide (CO) and formic acid (HCOOH) is highly desirable. These two-electron products are relatively simple to generate. Additionally, they are easy to store, transport, and integrate into existing industrial processes, enabling efficient use of surplus renewable energy within the carbon economy In this study, we present a novel electrocatalytic system comprising nickel single atom catalyst (Ni-SAC) sites uniformly dispersed within porous carbon nanofibers (Ni-CNFs) doped with sulfur (S) atoms, for the selective CO 2 electroreduction (ECCR). Electrospinning is an attractive synthesis process due to its high throughput, uniform and highly tuneable catalyst composition, and sustainable operation. The porous fiber morphology is also beneficial to the catalytic activity, since it prevents catalytic site (Ni in this case) leaching, prolongs electrolyte-catalyte contact, and provides an extended conductive matrix. Single-atom catalysts (SACs), particularly nitrogen-doped carbon-based ones with M-N4 structures, are promising for CO2-to-CO conversion. The uniformly dispersed Ni species facilitate the suppression of the competing hydrogen evolution reaction (HER) , yielding a highly specific electrocatalytic process. The synthesized Ni-CNFs exhibit a remarkable electrocatalytic performance, manifesting a current density of 200 mA/cm 2 (at -0.8V vs. RHE). However, their symmetric electron distribution can hinder CO2 activation. Introducing heteroatoms or nitrogen vacancies breaks this symmetry, enhancing activity. The incorporation of S heteroatoms within the porous matrix of the carbon nanofibers further contributes to enhanced catalytic activity. The optimized S-doped Ni-CNF electrode displays an impressive Faradaic efficiency (FE) for the CO production exceeding 95%, affirming the exceptional selectivity of the Ni-SACs. This enhancement can be assigned to the change in charge density, broken symmetry and excess electron density on the Nickel sites. Some major contributing factors, are their excess electron density and lower electronegativity as compared to N, which helps in breaking the M-N4 symmetry, leading to a more active SAC site. Dopants can also adjust the binding strength of intermediates to the metal center, optimizing reaction pathways and reducing energy barriers. These sites thus provide highly active centers for CO 2 adsorption and conversion, and the underlying mechanism will be elucidated with the help of in-situ electrochemical impedance spectroscopy (EIS) and allied electrochemical techniques. The synergistic combination of atomically precise catalyst sites and heteroatom doping underscores the potential of chemically tailored porous carbon nanofibers hosting Ni-SACs, as a viable platform for efficient CO 2 electroreduction. This study will provide a crucial bridge between the experimental observations and mechanistic theory of heteroatom doping of SACs for enhanced ECCR. Figure 1