Ni‐Fe Layered Double Hydroxide Nanosheets Supported on Exfoliated Graphite for Efficient Urea Oxidation in Direct Urea Fuel Cells

Abstract

Urea-rich wastewater can cause serious eutrophication problem to the water environment. On the other hand, urea is a potential fuel with high energy density, which can be effectively utilized by direct urea fuel cell. In this work, exfoliated graphite (EG) with high surface area and electrical conductivity was obtained by microwave irradiation, which was used to support the NiÀ Fe layered double hydroxide (LDH), leading to a highly efficient and low-cost urea oxidation catalyst. Compared with commercial RuO 2 , the as-prepared NiÀ Fe LDH/EG exhibited a lower onset potential of 1.25 V vs. reversible hydrogen electrode as well as a lower Tafel slope of 44 mV dec À 1 . The catalyst durability was also proved to be excellent. The optimized Ni/Fe molar ratio was confirmed to be 3 : 1, while the most suitable catalyst/EG ratio was 3 : 50. When applied in a dual-electrolyte direct urea fuel cell, the peak power density reached 12 mW cm À 2 , and the long-term discharge was also stable with negligible voltage loss at 10 mA cm À 2 for 3 h. Such a low-cost and efficient urea oxidation catalyst can be widely utilized in future direct urea fuel cells, which achieve wastewater treatment and renewable electricity generation at the same time.

Efficient ammonia photosynthesis from nitrate by graphene/Si Schottky junction integrated with Ni–Fe LDH catalyst

“…For the Fe 2p spectrum, there are two major spin–orbital peaks at the binding energies of 723.5 eV and 710.5 eV, which are assigned to Fe 3+ 2p 1/2 and 2p 3/2 orbitals, respectively. 39 Another peak located at 716.0 eV is associated with the satellite peak. 27 As for the Ni 2p spectrum, the two peaks at 873.2 eV and 855.4 eV are assigned to Ni 2+ 2p 1/2 and 2p 3/2 orbitals, accompanied by two shake-up satellite peaks at 879.1 eV and 860.8 eV.…”

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

“…[79] This limitation further impacts the overall energy density of the DUFC because it is notably greater compared to the oxidation potential of urea (À 0.46 V vs SHE). Therefore, to create more efficient UOR system, the modification of single nickel metals with another transition metal, such as Cr, [64] Mo, [65,80] Mn, [65,68] Fe, [81] Co, [27,67,[82][83][84] Cu, [78] Zn, [46] Sn, [85] Bi, [69] W, [86] and Pd, [87] has been reported to successfully overcome this limitations. These bimetallic Ni-based catalysts are predominantly synthesized using simple methods, such as hydrothermal or chemical deposition techniques.…”

“…There are still many interesting Ni-metal combinations that have potency to be developed for DUFC, as demonstrated by their UOR activities. For instance, layered double hydroxide Ni-Fe [81] was modified with exfoliated graphite as a carbon-based material via microwave irradiation techniques, resulting in a lower onset potential of 1.25 V vs. RHE and a reduced Tafel slope of 44 mV dec À 1 . Furthermore, the decoration process of Ni-Mn with carbon nanofibrous [89] produce an excellent current density of 120 mA cm À 2 g À 1 with an onset potential of 290 mV (vs. Ag/ AgCl) in urea oxidation.…”

Recent Advances on Transition‐Metal‐Based Layered Double Hydroxides Nanosheets for Electrocatalytic Energy Conversion

“…CoFeCr-LDHs 0.33 M urea 1.305 10 85 [129] NiMoV-LDHs 0.33 M urea 1.40 100 24.29 [130] FQD/CoNi-LDHs 0.5 M urea 1.36 10 17 [131] NiMn-LDHs 0.5 M urea 1.351 20 38.9 [133] NiCo-LDHs 0.33 M urea 1.36 50 45 [134] pa-NiFe-LDHs NS 0.33 M urea 1.362 30 33 [135] Cu-Ni3S2@NiFe-LDHs-200 0.5 M urea 1.319 100 37.78 [136] NiFe-LDHs-F-4 0.33 M urea 1.44 50 31 [137] NiAl-LDHs 0.33 M urea 1.42 10 59.8 [30] CoNi-LDHs-3 0.33 M urea 1.39 100 16 [138] NiFe-LDHs/EG 0.33 M urea 1.34 50 44 [139] Ce(OH)3@NiFe-LDHs 0.5 M urea 1.40 10 30.3 [140] H-NiFe-LDHs 0.33 M urea 1.397 10 41.7 [141] MoS2/Ni3S2/NiFe-LDHs 0.5 M urea 1.396 100 36 [142] NiCo-LDHs-[MoS4] 2− 0.33 M urea 1.34 10 29 [143] CoMn-LDHs 0.33 M urea 1.326 10 73 [144]…”