Bulk Bi and Bi Decorated Pt Thin Film Electrodes: From Formic Acid Oxidation to CO<sub>2</sub> Reduction
Bibliographic record
Abstract
The electrochemical reduction of CO2 has the potential to offer an elegant approach to the reduction of greenhouse gas emissions, while also providing diverse chemicals useful in organic synthesis or as liquid fuels for renewable energy storage.[1, 2] Copper is the most extensively studied catalyst nowadays for CO2 reduction as it is currently the only known metal to produce significant amount of hydrocarbons and alcohols such as ethanol, ethane or ethylene.[3] Unfortunately, the selectivity and stability of copper electrodes are rather low.[4] Other well known catalysts, such as Pt, Ni, Co or Fe have low selectivity for CO2 reduction and produce mostly H2.[5] On the other hand, catalysts such as Hg, Cd, Pb or Sn, which are poor hydrogen evolution catalysts, displayed interesting selectivity for CO2 reduction to formate. Unfortunately, they do so at high overpotentials.[6] Recently, single crystals studies showed that Pt(111)-Bi displayed an higher activity than Pt(111) itself for CO2 reduction at low overpotentials (between -0.64 and -1.04V vs SCE).[7] Combined with the high activity of Pt(111)-Bi catalysts for formic acid oxidation, this suggests that these catalysts could act as bifunctionnal catalysts, i.e., active for both the oxidation of formic acid to CO2and the reverse reaction. Unfortunately, the products formed were not identified in this study. It is known that preferentially (100) oriented Pt thin films decorated with Bi adatoms also display an improved activity for HCOOH oxidation.[8] Hence, in this study, we will study the catalytic performances of preferentially (100) oriented Pt thin films decorated with various amounts of Bi for CO2electroreduction (Fig. 1). Products analysis was performed by gas chromatography (hydrogen, carbon monoxide, methane, ethane, and ethylene) and ion chromatography (formate). As expected, on bare preferentially (100) oriented Pt thin film, the main product is H2for the whole range of potential investigated. This holds true when a monolayer of Bi is added onto the Pt surface. However, thicker Bi deposits prepared by electrodeposition at -0.21V displayed improved current efficiency for the production of formate. For these deposits, formate production at -1.6V increases from 20% for a deposit of 0.1C/cm2 to 74% for a 5C Bi deposit. This value is slightly lower than for bulk Bi deposits obtained by potentiostatic electrodeposition on titanium at -0.21V, which reached an 82% faradic efficiency at -1.5V. On the other hand, the overall current density at -1.5 V modestly increases from -2.2 mA/cm2 at bulk Bi to -2.9mA/cm2at a 1C Bi deposit on a preferentially (100) oriented Pt thin film, likely due to an increase of active surface area. The influence of the Bi deposition charge and surface orientation on the electrocatalytic performances for CO2reduction, as well as the durability of the catalyst will be further described in details. References [1] S.A. Akhade, W. Luo, X. Nie, N.J. Bernstein, A. Asthagiri, M.J. Janik, Phys. Chem. Chem. Phys., 16 (2014) 20429-20435. [2] K.J.P. Schouten, F. Calle-Vallejo, M.T.M. Koper, Angew. Chem. Int. Ed., 53 (2014) 10858-10860. [3] Y. Hori, I. Takahashi, O. Koga, N. Hoshi, J. Mol. Catal. A: Chem., 199 (2003) 39-47. [4] Y. Hori, H. Konishi, T. Futamura, A. Murata, O. Koga, H. Sakurai, K. Oguma, Electrochim. Acta, 50 (2005) 5354-5369. [5] M. Azuma, K. Hashimoto, M. Hiramoto, M. Watanabe, T. Sakata, J. Electrochem. Soc., 137 (1990) 1772-1778. [6] Q. Wang, H. Dong, H. Yu, J. Power Sources, 271 (2014) 278-284. [7] C.M. Sánchez-Sánchez, J. Souza-Garcia, E. Herrero, A. Aldaz, J. Electroanal. Chem., 668 (2012) 51-59. [8] E. Bertin, S. Garbarino, D. Guay, Electrochim. Acta, 134 (2014) 486-495. Figure 1
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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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".