Crystallization of NiCo MOF-74 on a Porous NiO Film as an Anode for the Urea/H₂O₂ Fuel Cell

Abstract

NiCo-MOF-74 crystallized directly on the surface of porous NiO (p-NiO) film using a solvothermal method is proposed as an effective electrocatalyst for the anode in direct urea fuel cells. A nickel-to-cobalt ratio of 4:1 was found to show optimum catalytic activity toward urea oxidation with significant current enhancement in comparison to other electrodes, including Ni foil and p-NiO. At optimized conditions in an electrolyte solution of 3.0 M KOH and 1.0 M urea, a current density of around 110 mA cm −2 with a maximum power density of 4131 μW cm −2 can be produced. This is ascribed to the increase of the active surface area over conventional nickel-based anodes, providing an abundance of active sites for urea oxidation. Excellent stability and reproducibility over 15 h application in a direct urea fuel cell was obtained with cell voltage of ∼0.6 V. Powder X-ray diffraction shows the crystalline MOF film remains intact after chronoamperometry tests, and after fuel cell application, illustrating applicability in real devices.

Advancements in Ni‐based Catalysts for Direct Urea Fuel Cells: A Comprehensive Review

“…As the KOH concentration is raised from 0.1 M to 4 M (Figure 1a), a noticeable shift towards lower onset potentials depicted from + 0.36 V vs. Ag/AgCl to + 0.25 V vs. Ag/AgCl. [34] In addition, an enhancement in the OCV from 0.4 to 0.55 V was observed when 5 M KOH was used as the electrolyte (Figure 1b). [50] As the result, a significant increase of the maximum power density from 1.7 to 11.2 mW cm À 2 could be achieved (Figure 1b).…”

“…The preparation of Ni-based MOFs can be accomplished through various techniques, such as solvothermal methods, providing tailored structures for efficient urea electrooxidation. [34] The synergy between MOF architecture and nickel catalysis offers the potential to significantly enhance the performance of DUFCs, providing a cleaner and more sustainable path for energy conversion. Therefore, it is essential to delve into the potential of Ni MOFs as catalysts in the electrochemical urea reactions within DUFCs.…”

“…Perfluoro sulfonic acid ionic exchange membrane/cation exchange membrane modifying 2D-3D structures of nickel to further increase its catalytic active sites. [31][32][33][34] On the other hand, it is theoretically conceivable to enhance the open circuit voltage (OCV) of DUFC. OCV refers to the voltage measured across the fuel cell when no current is flowing and offers valuable insights into the cell's electrochemical potential.…”

“…Ni-Se/NF [96] 0. NiCo MOF-74 @porous NiO [34] 1/3 NiCo-BDC-S-6 [100] 0. Single nickel oxides catalyst is easily deactivated under harsh catalytic condition, thus most reports regarding DUFC with nickel oxides/hydroxides anode were combined with another metal or oxides such as cobalt and copper.…”

High-pressure study of a 3d–4f heterometallic CuEu–organic skeleton

“…Research into the synthesis and application of crystalline metal-organic frameworks (MOFs) has grown in the last two decades, and studies related to the synthesis, application and development of MOF materials has witnessed explosive growth. The versatile chemical composition, network structures and pore regimes in MOFs allows the pore size, surface area and surface functionality to be tuned, offering advantages over other porous materials in gas storage (Tu et al, 2019;Mowbray et al, 2008;Chen et al, 2021), separation (Bae et al, 2008;Daglar et al, 2022), catalysis (Tian et al, 2023), drug delivery (Ding et al, 2022;Lin et al, 2019;Luo et al, 2019), sensors (Guo et al, 2014;Meilikhov et al, 2013) and fuel cells and supercapacitors (Putri et al, 2023;Xu et al, 2022). The performance of MOFs in such applications depends upon their thermal, chemical and mechanical stability.…”