Implementing Catalysts into Electrospun Composite Carbon Nanofiber (CNF) Electrodes for Ammonia Production from Photoelectrocatalytic Nitrate Reduction

Abstract

While novel carbon nanomaterials can serve as electrodes with exceptional electrical properties, carbon nanofibers (CNFs) merit further investigation for applications as electrodes in environmentally-relevant photoelectrocatalysis. Tunable, durable CNF structures can be easily synthesized as a convenient framework for catalyst implementation. Herein we investigate how catalysts can be integrated into carbon nanofiber mats to enhance the photoelectrocatalysis of nitrate reduction. As a frequent contaminant in agriculturally-intensive regions, the negative value of nitrate containing streams may be used to produce ammonia as a value-added product and to improve water quality in the resulting output stream. Catalysts were implemented using different methods (in situ sol gel, chemical reduction, electrochemical) on two different CNF composites (with and without titanium dioxide). We focus on copper as a catalyst due to its promising performance and economic advantage over traditional platinum group metals. After thorough characterization of the catalyst-CNF frameworks via XPS, XRD, Raman, the catalyst performance was measured by nitrate reduction product selectivity, catalyst lifetime, and Faradaic efficiency. The flexibility of CNF synthesis and catalyst implementation will provide photoelectrodes with properties desirable for the electrochemical reduction of nitrate in environmental conditions to generate valuable products. This work will help identify the types and properties of next-generation carbon composite electrode materials that are most promising for resource recovery and for improving photoelectrochemical catalytic cells purposed for drinking water treatment.