Pathway Manipulation via Ni, Co, and V Ternary Synergism to Realize High Efficiency for Urea Electrocatalytic Oxidation

Abstract

Ni is the one of most efficient active sites for triggering urea electrooxidation (UOR); however, ’it is hard to achieve higher activity and stability with only the Ni site. To address issues such as dehydrogenation, C–N bond breakage, and catalyst poisoning caused by carbonaceous fragments simultaneously, manipulating a pathway via building a multi-synergistic system is essential. Therefore, we constructed a Co, V co-doped NiS2 ternary collaborative system to achieve energy-saving urea electrooxidation with an emphasis on catalytic mechanism investigation. The optimal ternary catalyst exhibited good urea electrooxidation activity (77 mA cm–2 at 1.5 V vs RHE), stability, and hydrogen production (143 L min–1 gcat –1 at 1.8 V vs RHE). Based on X-ray photoelectron spectroscopy, in situ electrochemical Raman spectroscopy, an in situ electrochemical mass spectrometry isotope tracing experiment, and the density functional theory study, the roles of Ni, Co, and V elements were clearly revealed. The extended superexchange interaction not only enhanced the electron transmission capacity between Ni and S but also accelerated the electron transfer between urea and the catalyst. Anti-CO poisoning experiments indicated that the existence of Co can accelerate the oxidation of carbonaceous intermediate products and improve the catalyst stability. More importantly, we found that N2 was formed through the urea intermolecular N–N coupling process under the catalysis of metal sulfide. The strategy and mechanism proposed herein give a deeper understanding of UOR catalyzed by metal sulfides.

Cobalt-Vanadium Layered Double Hydroxides Nanosheets as High-Performance Electrocatalysts for Urea Oxidation Reaction

“…S6), the equivalent series resistance (RESR) and charge transfer resistance (Rct) values are summarized in Table S2. On the basis of these results, the relatively low RESR (2.09 Ω) and Rct (1.75 Ω) of CoV-LDHs demonstrated the superior electronic and ionic charge transfer ability for UOR 31 . Furthermore, the durability of the CoV-LDHs electrocatalyst was also investigated via a chronopotentiometry (CP) test at 10 mA•cm −2 for 10 h (Fig.…”

A doping element improving the properties of catalysis: in situ Raman spectroscopy insights into Mn-doped NiMn layered double hydroxide for the urea oxidation reaction

“…It is useful to characterize the UOR process. [23][24][25] To date, the in situ characterization of NiMn doublecomponent electrocatalysts for the UOR have been rarely studied. Herein, we employed in situ SERS in addition to conventional electrochemical techniques to describe the apparent electrocatalytic behavior of these excellent catalysts and to gain more detailed information about species evolution in NiMn layered double hydroxides (NiMn LDHs) in the UOR process.…”

Co-doped Ni–Mo oxides: highly efficient and robust electrocatalysts for urea electrooxidation assisted hydrogen production

“…[18][19][20][21][22] However, the complex sixelectron reaction of UOR inherently has sluggish kinetics, 23 which require catalysts to accelerate the reaction rate. 24 Nibased catalysts [24][25][26][27][28] have been widely reported in UOR because Ni metal sites can efficiently decompose urea into NH 3 and CO 2 . 27 With the Mo element, Ni-Mo-based catalysts have recently attracted increasing attention because of the improved long-term stability in UOR.…”

“…24 Nibased catalysts [24][25][26][27][28] have been widely reported in UOR because Ni metal sites can efficiently decompose urea into NH 3 and CO 2 . 27 With the Mo element, Ni-Mo-based catalysts have recently attracted increasing attention because of the improved long-term stability in UOR. [29][30][31] However, due to the insufficient urea absorption and desorption of reaction intermediates (e.g., *COO) from the electrode interface, 32 current UOR catalysts still need improvements in catalytic activity and stability.…”

“…Heteroatomic doping has been demonstrated to be an effective strategy to improve the electrochemical properties of the catalyst by adjusting the structure of electrons with doped atoms and tuning the adsorption strength of the catalyst to substrates or intermediates. 27,33 It has been reported that metal doping (e.g., Co, Mn, and V) can promote the formation of highvalence nickel to improve the electrocatalytic activity of urea; 27,34,35 while N, Ce doping can promote the desorption of reactants to improve the stability of the catalyst. 36,37 However, to the best of our knowledge, studies on Co doping for improvement in the UOR activity have not been sufficiently studied in previous reports.…”