Lowering Electrocatalytic CO <sub>2</sub> Reduction Overpotential Using N-Annulated Perylene Diimide Rhenium Bipyridine Dyads with Variable Tether Length
Bibliographic record
Abstract
We report the design, synthesis, and characterization of four N-annulated perylene diimide (NPDI) functionalized rhenium bipyridine [Re(bpy)] supramolecular dyads. The Re(bpy) scaffold was connected to the NPDI chromophore either directly [ Re(py-C0-NPDI) ] or via an ethyl [ Re(bpy-C2-NPDI) ], butyl [ Re(bpy-C4-NPDI) ], or hexyl [ Re(bpy-C6-NPDI) ] alkyl-chain spacer. Upon electrochemical reduction in the presence of CO 2 and a proton source, Re(bpy-C2/4/6-NPDI) all exhibited significant current enhancement effects, while Re(py-C0-NPDI) did not. During controlled potential electrolysis (CPE) experiments at E appl = −1.8 V vs Fc +/0, Re(bpy-C2/4/6-NPDI) all achieved comparable activity (TON co ∼ 25) and Faradaic efficiency (FE co ∼ 94%). Under identical CPE conditions, the standard catalyst Re(dmbpy) was inactive for electrocatalytic CO 2 reduction; only at E appl = −2.1 V vs Fc +/0 could Re(dmbpy) achieve the same catalytic performance, representing a 300 mV lowering in overpotential for Re(bpy-C2/4/6-NPDI) . At higher overpotentials, Re(bpy-C4/6-NPDI) both outperformed Re(bpy-C2-NPDI), indicating the possibility of coinciding electrocatalytic CO 2 reduction mechanisms that are dictated by tether-length and overpotential. Using UV-vis-nearIR spectroelectrochemistry (SEC), FTIR SEC, and chemical reduction experiments, it was shown that the NPDI-moiety served as an electron-reservoir for Re(bpy), thereby allowing catalytic activity at lower overpotentials. Density functional theory studies probing the optimized geometries and frontier molecular orbitals of various catalytic intermediates revealed that the geometric configuration of NPDI relative to the Re(bpy)-moiety plays a critical role in accessing electrons from the electron-reservoir. The improved performance of Re(bpy-C2/4/6-NPDI) dyads at lower overpotentials, relative to Re(dmbpy), highlights the utility of chromophore electron-reservoirs as a method for lowering the overpotential for CO 2 conversion.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".