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Abstract 2D early transition metal carbide and nitride MXenes have intriguing properties for electrochemical energy storage and electrocatalysis. These properties can be manipulated by modifying the basal plane chemistry. Here, mixed transition metal nitride MXenes, M‐Ti4N3Tx(M = V, Cr, Mo, or Mn; Tx= O and/or OH), are developed by modifying pristine exfoliated Ti4N3TxMXene with V, Cr, Mo, and Mn salts using a simple solution‐based method. The resulting mixed transition metal nitride MXenes contain 6–51% metal loading (cf. Ti) that exhibit rich electrochemistry including highly tunable hydrogen evolution reaction (HER) electrocatalytic activity in a 0.5mH2SO4electrolyte as follows: V‐Ti4N3Tx> Cr‐Ti4N3Tx> Mo‐Ti4N3Tx> Mn‐Ti4N3Tx> pristine Ti4N3Txwith overpotentials as low as 330 mV at −10 mA cm−2with a charge‐transfer resistance of 70 Ω. Scanning electrochemical microscopy (SECM) reveals the electrochemical activity of individual MXene flakes. The SECM data corroborate the bulk HER activity trend for M‐Ti4N3Txas well as provide the first experimental evidence that HER results from catalysis on the MXene basal plane. These electrocatalytic results demonstrate a new pathway to tune the electrochemical properties of MXenes for water splitting and related electrochemical applications.
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Operando Tracking of Resistance, Thickness, and Mass of Ti 3 C 2 T x MXene in Water‐in‐Salt Electrolyte
Abstract MXenes are among the fastest‐growing families of 2D materials, promising for high‐rate, high‐energy energy storage applications due to their high electronic and ionic conductivity, large surface area, and reversible surface redox ability. The Ti3C2TxMXene shows a capacitive charge storage mechanism in diluted aqueous LiCl electrolyte while achieving abnormal redox‐like features in the water‐in‐salt LiCl electrolyte. Herein, variousoperandotechniques are used to investigate changes in resistance, mass, and electrode thickness of Ti3C2Txduring cycling in salt‐in‐water and water‐in‐salt LiCl electrolytes. Significant resistance variations due to interlayer space changes are recorded in the water‐in‐salt LiCl electrolyte. In both electrolytes, conductivity variations attributed to charge carrier density changes or varied inter‐sheet electron hopping barriers are detected in the capacitive areas, where no thickness variations are observed. Overall, combining thoseoperandotechniques enhances the understanding of charge storage mechanisms and facilitates the development of MXene‐based energy storage devices.
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- Award ID(s):
- 2041050
- PAR ID:
- 10569251
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 15
- Issue:
- 20
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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