【公開日：2023.08.01】【最終更新日：2023.04.25】
課題データ / Project Data
課題番号 / Project Issue Number
22KU1050
利用課題名 / Title
Molten salt-assisted fabrication of NiFe/C composite for OER
利用した実施機関 / Support Institute
九州大学
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）物質・材料合成プロセス/Molecule & Material Synthesis（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）次世代ナノスケールマテリアル/Next-generation nanoscale materials（副 / Sub）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion
キーワード / Keywords
電極材料
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Yip SenPo
所属名 / Affiliation
九州大学先導物質化学研究所
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
KU-504：レーザラマン分光光度計装置群
KU-517：ナノ炭素燃料電池評価装置群
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Carbon-supported transition metal nanostructures (TMs/C) have been attracting significant interest for electrochemical water splitting, which includes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Pyrolysis is a common method used to prepare TMs/C electrocatalyst due to its simplicity. Here we developed a molten salt assisted pyrolysis to fabricate NiFe particle/C composite for improved OER performance. Compare with non-molten salt assisted pyrolysis, the molten salt assisted pyrolysis shows better OER performance as (i) improved graphitization of the carbon layer which enhance charge exchange efficiency and (ii) enhanced the amount of the oxygen species (M-O and M-OH bond) on the surface of the NiFe particles which lower the reaction barrier. These findings provide a promising approach for designing and synthesizing high-performance TMs/C electrocatalysts for energy conversion and storage applications.
実験 / Experimental
In molten salt-assisted pyrolysis, glucose is used as a carbon source and mixed with metal precursors (nickel chloride and iron chloride) and a molten salt (eutectic NaCl/KCl system). The mixture is then placed in a ceramic boat and placed in a tube furnace. The pyrolysis is performed under an Ar flow and naturally cooled to room temperature. The resulting product is washed with DI water to remove the salt, and the sample is dried in an oven and characterized using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. To evaluate the electrochemical activity, a three-electrode system is used consisting of a working electrode (TMs/C catalyst on glassy carbon), a reference electrode (Ag/AgCl), and a counter electrode (graphite rod) with KOH as an electrolyte. The electrochemical properties of the catalyst are characterized by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The catalyst's performance is evaluated by measuring the overpotential, Tafel slope, and current density at different potentials.
結果と考察 / Results and Discussion
Upon conducting SEM and XRD analysis, it was determined that the black powder obtained consisted of metallic NiFe particles with a face-centered cubic structure that had grown on carbon flakes. By optimizing the Fe:Ni ratio, the overpotential at 10 mA cm-2 could be significantly reduced, reaching a low of 296.6mV, and the Tafel slope could be lowered to a mere 37.91mV dec-1. In comparison to the reference sample (pyrolysis without molten salt), the OER performance of the catalyst was significantly improved.
Upon further characterization, two primary contributing factors were discovered that led to this improved performance. The first was the improved graphitization of the carbon templates, which was confirmed by a higher Ig/Id ratio of the carbon layer during Raman spectroscopy analysis, leading to better electricity conduction. The second contributing factor was the increase in the amount of surface oxygen species (M-O and M-OH bonds) on the NiFe particle surface. This increase is believed to be due to a better oxygen-trapping effect in the molten salt, leading to the formation of more surface oxygen species.
These results highlight the immense potential of molten salt-assisted pyrolysis as an innovative method for preparing electrocatalysts for energy conversion and storage applications.
図・表・数式 / Figures, Tables and Equations
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件