3D Hierarchical Core–Shell Nanostructured Arrays on Carbon Fibers as Catalysts for Direct Urea Fuel Cells

Abstract

reaction (OER), [4] which limited the stability of the catalyst and the DUFC performance.In general, OER occurs at the anodic surface under a higher electrode potential, and it is hypothesized that decreasing the anode UOR potential would effectively eliminate the OER. On the other hand, ORR suffers from sluggish reaction kinetics due to the large activation process involved in cleaving the double bonds in an O 2 molecule. [5] Despite the vast interest in this area, all reported DUFCs are based on precious metal ORR catalysts, including Pt/C, [1] Pd, [6] Pd/C@Ti, [7] and Ag/C, [2] which defeats the cost advantages of DUFCs. Furthermore, all of the efforts on DUFCs have been based on the use of two different catalysts for UOR and ORR. Recently, cobalt oxide (Co 3 O 4 )-based nanocatalysts have emerged as a potential bifunctional catalyst due to their ability to effectively eliminate the OER constraints and their preferable adsorption of O 2 molecules via the Pauling mode (Co … (O ads O)). [8] However, the UOR activity of Co 3 O 4 is hampered by the poisoning of the catalyst surface by the oxidation intermediates. [9] The peroxide species (HO 2− ) generated under an alkaline medium during the ORR deteriorates the catalytic stability of Co 3 O 4 . [10] These challenges could be overcome with a surface engineering of Co 3 O 4 nanostructures with specific UOR and ORR catalysts in the form of core-shell architectures.Furthermore, the conventional techniques used for the modification of DUFC electrodes with nanocatalysts involve tedious protocols such as substrate pretreatment, slurry preparation, tedious catalyst loading/coating, binder selection, blockage of active sites via binder, time consumption, high resistance, etc. [11] These difficulties could be circumvented if the nanocatalysts could be directly grown over the electrode materials. Accordingly, we present here a direct growth of core-shell nanostructures over carbon cloth (CC) fibers and address the challenges of Co 3 O 4 toward UOR and ORR electrokinetics via a decoration of Co 3 O 4 core with, respectively, NiO and MnO 2 shells. Results and DiscussionThe scanning electron microscopy (SEM) image of the bare CC (Figure 1a) clearly reveals the ordered woven structure with a smooth surface and interconnected 2D carbon fibers. From Figure 1b,c, it is clear that the CC nanofibers are homogeneously enveloped with the smooth surfaced and uniformly aligned Co 3 O 4 nanowires with sharp tips. The mean diameter and length of Co 3 O 4 nanowires are found to be 40 nm and 1.7 µm, respectively.Bifunctional cobalt oxide (Co 3 O 4 ) nanowire catalysts grown on carbon cloth (CC) fibers and their modification with nickel oxide (NiO) and manganese dioxide (MnO 2 ) to produce core-shell nanoarchitectures are explored as catalysts for urea oxidation reaction and oxygen reduction reaction in direct urea fuel cells (DUFC). Based on a systematic electrochemical characterization of the catalyst, the as-developed core-shell nanoarchitectures are optimized toward DUFC performance....

Interaction of bacteria and archaea in a microbial fuel cell with ITO anode

“…8 At present, more and more choices have got to fabricate or modify the electrode of MFCs, with nanomaterials, nanocomposites, graphene sheet and graphene oxides owing to their high surface area, porosity and prompt electron conduction properties. [9][10][11][12][13] The results showed that the electrodes fabricated or modied by nonamaterials exhibited excellent electrochemical activity. Signicant redox peaks have found in cyclic voltammograms and electricity production of the MFCs also obtained.…”

A Lattice‐Oxygen‐Involved Reaction Pathway to Boost Urea Oxidation

“…The urea oxidation reaction (UOR) is known as a central chemical reaction in the area of energy storage, urea fuel cells, de‐ureation of wastewater, artificial kidneys, and so on. Especially in the application of clean energy conversion and storage, UOR can work as an alternative anodic reaction to oxygen evolution reaction (OER), which provides electrons for hydrogen evolution, CO 2 reduction, and N 2 reduction reactions.…”

Facile Non‐enzymatic Lactic Acid Sensor Based on Cobalt Oxide Nanostructures

“…It is seen from Figure 3(a) that sample-3 shows excellent redox activity as compared to other prepared materials. In alkaline media during the water oxidation, after the absorption of OH À ions, Co 2 + is changed into Co 3 + , and further Co 3 + is oxidized into Co 4 + at high potentials [41]. It is evident that well controlled and resolved redox peaks are mainly coming in case of sample-3 for the lactic acid.…”

“…It is evident that well controlled and resolved redox peaks are mainly coming in case of sample-3 for the lactic acid. The existence of Co 2 + /Co 3 + centers in the solution further efficiently oxidizes the lactic acid into pyruvic acid as can be seen from the below chemical reactions [41]. Furthermore, we have carried out the CV measurement in the presence of glucose that indicates a broad oxidation peak in 0.1 mM glucose but it is not well resolved as shown in Figure 3(c).…”