Role of Mass Transfer Phenomena in Electrochemical Nitrate Reduction: A Case Study Using Ti and Ag-Modified Ti-Hollow Fiber Electrodes.

IF 4.3 Q2 ENGINEERING, CHEMICAL
ACS Engineering Au Pub Date : 2024-12-24 eCollection Date: 2025-02-19 DOI:10.1021/acsengineeringau.4c00035
Ainoa Paradelo Rodríguez, Guido Mul, Bastian T Mei
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引用次数: 0

Abstract

Decentralized electrochemical reduction of nitrate into ammonium is explored as a viable approach to mitigate nitrate accumulation in groundwater. In this study, tubular porous electrodes made of titanium (termed hollow fiber electrodes or HFEs) were successfully modified with silver (Ag) nanoparticles through electrodeposition. Under galvanostatic control and in acidic electrolyte, Ag deposition on Ti HFE resulted in an increase in the Faradaic efficiency for ammonium formation from low concentrations of nitrate (50 mM), but only under reaction conditions of restricted mass transport. For conditions of favorable transport, facilitated by an inert gas flow (Ar) exiting the pores, a higher nitrate conversion but an increase in hydroxylamine selectivity at the expense of the ammonium selectivity are observed for Ti/Ag hollow fiber electrodes. For Ti/Ag electrodes, it is concluded that ammonium formation is prevented by effective removal of surface intermediates. Remarkably, for unmodified Ti hollow fiber electrodes, the Faradaic efficiency to ammonium is significantly improved when operated at high current densities and in conditions of high mass transport. The selectivity to liquid products even surpasses the selectivity of Ti/Ag electrodes. These findings indicate that nitrate reduction to ammonium at Ti and Ti/Ag hollow fiber electrodes can be achieved at comparable rates but under distinctly different process conditions. In fact, for Ti electrodes, operation at a lower applied potential compared to Ti/Ag electrodes is feasible, ultimately resulting in reduced energy consumption. This study thus highlights the importance of controlling the interfacial electrode environment, particularly when comparing and evaluating the effectiveness of electrode materials in electrochemical nitrate reduction. The study also reveals that transport phenomena affect electrode material-dependent activity-selectivity correlations and must be considered in ongoing material development efforts.

传质现象在电化学还原硝酸盐中的作用:以Ti和ag修饰的Ti中空纤维电极为例。
探讨了分散电化学还原硝态氮为铵态氮的可行方法,以减少地下水中硝态氮的积累。在这项研究中,用钛制成的管状多孔电极(称为空心纤维电极或hfe)通过电沉积成功地用银(Ag)纳米粒子修饰。在恒流控制和酸性电解质条件下,Ti HFE上的Ag沉积导致低浓度硝酸盐(50 mM)生成铵的法拉第效率增加,但仅在限制质量输运的反应条件下。在惰性气体流(Ar)的促进下,Ti/Ag中空纤维电极的硝酸盐转化率更高,但羟胺选择性的增加以牺牲铵选择性为代价。对于Ti/Ag电极,可以通过有效去除表面中间体来阻止铵的形成。值得注意的是,对于未改性的Ti中空纤维电极,在高电流密度和高质量输运条件下,对铵离子的法拉第效率显著提高。对液体产物的选择性甚至超过了Ti/Ag电极的选择性。这些结果表明,在Ti和Ti/Ag中空纤维电极上,硝酸盐还原成铵的速率可以比较,但在明显不同的工艺条件下。事实上,对于Ti电极来说,与Ti/Ag电极相比,在较低的施加电位下工作是可行的,最终导致能耗降低。因此,本研究强调了控制界面电极环境的重要性,特别是在比较和评估电极材料在电化学硝酸还原中的有效性时。该研究还表明,传输现象影响电极材料依赖的活性-选择性相关性,必须在正在进行的材料开发工作中加以考虑。
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来源期刊
ACS Engineering Au
ACS Engineering Au 化学工程技术-
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期刊介绍: )ACS Engineering Au is an open access journal that reports significant advances in chemical engineering applied chemistry and energy covering fundamentals processes and products. The journal's broad scope includes experimental theoretical mathematical computational chemical and physical research from academic and industrial settings. Short letters comprehensive articles reviews and perspectives are welcome on topics that include:Fundamental research in such areas as thermodynamics transport phenomena (flow mixing mass & heat transfer) chemical reaction kinetics and engineering catalysis separations interfacial phenomena and materialsProcess design development and intensification (e.g. process technologies for chemicals and materials synthesis and design methods process intensification multiphase reactors scale-up systems analysis process control data correlation schemes modeling machine learning Artificial Intelligence)Product research and development involving chemical and engineering aspects (e.g. catalysts plastics elastomers fibers adhesives coatings paper membranes lubricants ceramics aerosols fluidic devices intensified process equipment)Energy and fuels (e.g. pre-treatment processing and utilization of renewable energy resources; processing and utilization of fuels; properties and structure or molecular composition of both raw fuels and refined products; fuel cells hydrogen batteries; photochemical fuel and energy production; decarbonization; electrification; microwave; cavitation)Measurement techniques computational models and data on thermo-physical thermodynamic and transport properties of materials and phase equilibrium behaviorNew methods models and tools (e.g. real-time data analytics multi-scale models physics informed machine learning models machine learning enhanced physics-based models soft sensors high-performance computing)
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