北京交通大学梁志琴团队报道了羟基丙酮电化学加氢制丙二醇质子耦合电子转移动力学中的缓冲供体穿梭。相关研究成果于2024年8月8日发表于国际一流学术期刊《美国化学会杂志》。

电化学加氢反应需要电极表面快速的质子耦合电子转移，其动力学与pH值密切相关。缓冲电解质被广泛用于在宽范围内调节pH值。然而，在解释内在pH依赖性时，应考虑缓冲物质的具体作用，这在当前的研究中很容易被忽视。

该文中，研究人员报道了在多晶铜电极上以56±5%的法拉第效率将来自甘油原料的羟基丙酮电化学氢化为丙二醇。柠檬酸盐、磷酸盐和硼酸盐缓冲电解质中的反应活性相当，包括不同的缓冲液特性和pH值。电动曲线表明，柠檬酸盐是铜表面上的一个阻断吸附物的位点，因此降低缓冲液浓度和增加pH值将提高反应速率；磷酸盐是一种显式质子供体，通过增加缓冲液浓度和降低pH值来促进界面速率，而硼酸盐是一种无害的缓冲液，可用于研究固有的pH效应。

结合原位SEIRAS，证明了水是柠檬酸盐和硼酸盐电解质中的主要质子源，重申了基于微动力学模型提出的机制的合理性。研究结果强调了缓冲体系对电催化动力学活性的内在复杂性。当诊断缓冲液电解质中由不同缓冲液身份和pH值组成的机制途径时，需要特别注意。

附：英文原文

Title: Buffering Donor Shuttles in Proton-Coupled Electron Transfer Kinetics for Electrochemical Hydrogenation of Hydroxyacetone to Propylene Glycol

Author: Guoquan Ma, Na Jiang, Yu Zhang, Dandan Song, Bo Qiao, Zheng Xu, Suling Zhao, Zhiqin Liang

Issue&Volume: August 8, 2024

Abstract: Electrochemical hydrogenation reactions demand rapid proton-coupled electron transfer at the electrode surface, the kinetics of which depend closely on pH. Buffer electrolytes are extensively employed to regulate pH over a wide range. However, the specific role of buffer species should be taken into account when interpreting the intrinsic pH dependence, which is easily overlooked in the current research. Herein, we report the electrochemical hydrogenation of hydroxyacetone, derived from glycerol feedstock, to propylene glycol with a faradaic efficiency of 56 ± 5% on a polycrystalline Cu electrode. The reaction activities are comparable in citrate, phosphate, and borate buffer electrolytes, encompassing different buffer identities and pH. The electrokinetic profile reveals that citrate is a site-blocking adsorbate on the Cu surface, thereby decreasing buffer concentration and increasing pH will enhance the reaction rate; phosphate is an explicit proton donor, which promotes the interfacial rate by increasing buffer concentration and decreasing pH, while borate is an innocent buffer, which can be used to investigate the intrinsic pH effect. Combined with in situ SEIRAS, we demonstrate that water is the primary proton source in citrate and borate electrolytes, reiterating the rationality of the proposed mechanism based on the microkinetic modeling. Our results emphasize the intrinsic complexity of the buffer system on the kinetic activity for electrocatalysis. It calls for special care when we diagnose the mechanistic pathway in buffer electrolytes convoluted by different buffer identities and pH.

DOI: 10.1021/jacs.4c05446

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c05446