Electrocatalytic Activity of Amorphous Ni-Nb-Y Alloys for the HER in Alkaline Water Electrolysis
Notice bibliographique
Résumé
Introduction: The recent development of anion exchange membranes (AEM) has renewed interest in alkaline water electrolysis for large-scale production of hydrogen gas. These systems can achieve current densities comparable to PEM-based systems while enabling the use of non-PGMs as catalyst materials. New electrocatalysts are required to interface with such AEMs in advanced alkaline water electrolyser designs. Amorphous alloys have previously been proposed as electrocatalysts due to their unique atomic structure, which results in electrochemical properties particularly suitable for catalysis. These properties include a high density of co-ordinatively unsaturated sites, a much greater solute solubility allowing for highly tunable homogeneous compositions, and a high stability against surface segregation of solute atoms [1-3]. To date, amorphous alloys have been underutilized as catalysts due to the lack of suitable methods to increase their electrochemically active surface area. Mechanical alloying and subsequent dealloying can be used to overcome this issue to yield 3D mesoporous and nanoporous amorphous structures. The present work assesses the role of structure and chemistry on the catalytic activity of Ni-Nb-Y amorphous alloys towards the hydrogen evolution reaction. Ni-based alloys exhibit some of the highest activity among the non-PGM catalysts while yttrium and niobium are excellent glass formers and offer interesting catalytic performance, particularly yttrium which has shown high catalytic activity when alloyed with nickel [4, 5]. Experimental Methods: Cryogenic ball milling of elemental powders was used to synthesize a novel high surface area amorphous Ni79.2Nb12.5Y8.3 alloy. Composite amorphous alloys with minor secondary crystalline phases (Ni5Y and Y2O3) were also synthesized and evaluated. X-ray diffraction and electron microscopy were used to analyze the alloy structures and particle morphology. Working electrodes were prepared by synthesizing catalyst suspensions consisting of the alloyed powder along with Nafion® 117 solution and iso-propanol and drop casting said suspensions on glassy carbon electrodes. Electrochemical characterization was assessed through steady state polarization (Tafel) curves, cyclic voltammetry, and AC impedance spectroscopy. Results and Discussion: The Ni79.2Nb12.5Y8.3 amorphous alloy exhibited improved intrinsic catalytic performance compared to nickel, and the addition of minor secondary crystalline phases, namely Ni5Y, resulted in even greater intrinsic performance. Electrochemical testing revealed this trend to be consistent even when testing amorphous composite materials containing higher (Ni81.3Nb6.3Y12.5) and lower (Ni77.1Nb18.8Y4.2) Y content. Tafel measurements for Ni-Nb-Y alloys can be seen in figure 1 with corresponding data summarized in table 1. These alloys highlight the improved catalytic performance to be a result of the secondary Ni5Y phase as opposed to the total alloying content. These results warrant further electrochemical characterization of multiphase amorphous nickel alloys with finely dispersed crystallinity for catalyst development. Conclusions and Future Work: The mechanical alloying process can be used to produce highly tunable chemical compositions where then the addition of finely dispersed secondary crystalline phases result in improved catalytic activity. The preliminary electrochemical results illustrate that mechanically alloyed Ni-based amorphous materials are promising catalyst precursors for clean electrochemical hydrogen production. References: [1] A. Molnar, G. Smith, and M. Bartok, Adv. Catal., 36, 329-383 (1989). [2] J. Deng, H. Li, and W. Wang, Catal. Today, 51, 113-125 (1999). [3] M. Carmo, R. Sekol, S. Ding, G. Kumar, J. Schroers and A. Taylor. ACS Nano, 5 (4) 2979-2983 (2011). [4] F. Rosalbino, S. Delsante, G. Borzone, and E. Angelini. Int. J. Hydrogen Energy, 33, 6696-6703 (2008). [5] F. Rosalbino, S. Delsante, G. Borzone and E. Angelini. J. Alloys Compd., 429, 270-275, (2007) Figure 1
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».