Electrocatalytic Activity of Pd, Pt, and Rh for the Electro-oxidation of Ethanol in Alkaline Electrolyte: An Online DEMS Study

Recent development and applications of differential electrochemical mass spectrometry in emerging energy conversion and storage solutions

Electrochemical energy conversion and storage are playing an increasingly important role in shaping the sustainable future. Differential electrochemical mass spectrometry (DEMS) offers an operando and cost-effective tool to monitor the evolution of gaseous/volatile intermediates and products during these processes. It can deliver potential-, time-, mass- and space-resolved signals which facilitate the understanding of reaction kinetics. In this review, we show the latest developments and applications of DEMS in various energy-related electrochemical reactions from three distinct perspectives. (I) What is DEMS addresses the working principles and key components of DEMS, highlighting the new and distinct instrumental configurations for different applications. (II) How to use DEMS tackles practical matters including the electrochemical test protocols, quantification of both potential and mass signals, and error analysis. (III) Where to apply DEMS is the focus of this review, dealing with concrete examples and unique values of DEMS studies in both energy conversion applications (CO2 reduction, water electrolysis, carbon corrosion, N-related catalysis, electrosynthesis, fuel cells, photo-electrocatalysis and beyond) and energy storage applications (Li-ion batteries and beyond, metal-air batteries, supercapacitors and flow batteries). The recent development of DEMS-hyphenated techniques and the outlook of the DEMS technique are discussed at the end. As DEMS celebrates its 40th anniversary in 2024, we hope this review can offer electrochemistry researchers a comprehensive understanding of the latest developments of DEMS and will inspire them to tackle emerging scientific questions using DEMS.

Potential-Dependent Mechanistic Study of Ethanol Electro-oxidation on Palladium

We herein used the density functional theory (DFT) method and the implicit continuum solvation model to study the potential-dependent mechanism of ethanol oxidation reaction (EOR) on palladium (Pd). Energy evolutions of the EOR on low-index Pd surfaces, including (111), (110), and (100), were obtained as a function of the electrode potential. Moreover, the onset potentials for key intermediates and products were calculated. In addition, the potential range for adsorbed ethanol as the most stable adsorption state for proceeding the EOR was determined to be between 0.15 and 0.78 V via the calculated Pourbaix diagrams when considering hydrogen underpotential deposition and Pd(II) oxide formation as competing reactions. Specifically, the behavior of Pd(111) as the dominating facet decided the overall activity of the EOR with onset potentials to acidic acid/acetate at 0.40 V, to carbon dioxide at 0.71 V, and to oxide formation at 0.78 V. Pd(110) was predicted to exhibit the optimal activity toward the EOR with the lowest onset potentials to both the first dehydrogenation process and carbon dioxide at 0.08 and 0.60 V, respectively. A computational potential-dependent mechanism of the EOR was proposed, which agrees well with the experimental curve of linear sweeping voltammetry on the commercial Pd/C electrocatalyst. Our study suggests that targeted control of products can be tuned with proper overpotential and thus provides a foundation for the future development of EOR electrocatalysts.