Ethanol Electro-oxidation on Pt/C Electrocatalysts: An “In Situ” Raman Spectroelectrochemical Study

Observation of NMR signals from samples with flat geometry: Application to in-situ analysis of a direct ethanol fuel cell

Most NMR samples are cylindrical, which is ideal for obtaining high-resolution NMR spectra, especially in superconducting magnets with a vertical bore. However, expanding NMR applicability to samples that are not necessarily cylindrical requires a new approach. In this study, we introduce a method for obtaining solution NMR signals from flat samples, such as flat containers or layered structures like a fuel cell. A flat rectangular NMR coil was developed for RF application and sensitive signal detection, while biplanar shim coils were designed using Bfieldtools and manufactured on multilayered printed circuit boards to improve NMR resolution. Water and ethanol molecules in flat rectangular and flat circular containers, as well as in a direct ethanol fuel cell, were observed with narrow NMR linewidths. We believe that our spectrometer design will enable NMR analysis of samples that need to be contained in flat structures and support in-situ analysis of various devices.

Ni3C/Ni3S2 Heterojunction Electrocatalyst for Efficient Methanol Oxidation via Dual Anion Co-modulation Strategy

Enhancing active states on the catalyst surface by modulating the adsorption-desorption properties of reactant species is crucial to optimizing the electrocatalytic activity of transition metal-based nanostructured materials. In this work, an efficient optimization strategy is proposed by co-modulating the dual anions (C and S) in Ni3C/Ni3S2, the heterostructured electrocatalyst, which is prepared via a simple hot-injection method. The presence of Ni3C/Ni3S2 heterojunctions accelerates the charge carrier transfer and promotes the generation of active sites, enabling the heterostructured electrocatalyst to achieve current densities of 10/100 mA cm-2 at 1.37 V/1.53 V. The Faradaic efficiencies for formate production coupled with hydrogen evolution approach 100%, accompanied with a stability record of 350 h. Additionally, operando electrochemical impedance spectroscopy (EIS), in situ Raman spectroscopy, and density functional theory (DFT) calculations further demonstrate that the creation of Ni3C/Ni3S2 heterointerfaces originating from dual anions' (C and S) differentiation is effective in adjusting the d-band center of active Ni atoms, promoting the generation of active sites, as well as optimizing the adsorption and desorption of reaction intermediates. This dual anions co-modulation strategy to stable heterostructure provides a general route for constructing high-performance transition metal-based electrocatalysts.

Role of Noncovalent Interactions on the Electrocatalytic Oxidation of Ethanol in Alkali Metal Hydroxide Solutions

Ethanol is considered to be one of the most promising fuels for fuel cells. However, ethanol fuel cells have a sluggish Faraday efficiency due to complex interactions between the electrolyte, electrode, and ethanol. Recent studies have further suggested that noncovalent interactions originated from the hydrated alkali metal cations and the adsorbed OH_ad at the Pt electrode surface also played an important role in the electron transfer. In this regard, the noncovalent interactions in different alkali metal hydroxide (AMH) solutions have been systematically investigated in this study, and it was observed that the noncovalent interactions could result in the occupation of the Pt electrode surface active sites and sluggish migration of ethanol molecules in the electrical double layer, significantly affecting the electro-oxidation efficiency. Further, it was concluded that the electro-oxidation efficiency in different AMH solutions followed the order of K⁺ > Na⁺ > Rb⁺ > Cs⁺ > Li⁺ due to the noncovalent interactions.