[MoS₄]^2–-Intercalated NiCo-Layered Double Hydroxide Nanospikes: An Efficiently Synergized Material for Urine To Direct H₂ Generation

Abstract

Substituting the energy-uphill water oxidation half-cell with readily oxidizable urea-rich urine, a ground-breaking bridge is constructed, combining the energy-efficient hydrogen generation and environmental protection. Hence, designing a robust multifunctional electrocatalyst is desirable for widespread implementation of this waste to fuel technology. In this context, here, we report a simple tuning of the electrocatalytically favorable characteristics of NiCo-layered double hydroxide by introducing [MoS4]2– in its interlayer space. The [MoS4]2– insertion as well as its effect on the electronic structure tuning is thoroughly studied via X-ray photoelectron spectroscopy in combination with electrochemical analysis. This insertion induces overall electronic structure tuning of the hydroxide layer in such a way that the designed catalyst exhibited favorable kinetics toward all the required reactions of hydrogen generation. This is why our homemade catalyst, when utilized both as a cathode and anode to fabricate a urea electrolyzer, required a mere ∼1.37 V cell potential to generate sufficient H2 by reaching the benchmark 10 mA cm–2 in 1 M KOH/0.33 M urea along with long-lasting catalytic efficiency. Other indispensable reason of selecting [MoS4]2– is its high-valent nature making the catalyst highly selective and insensitive to common catalyst-poisoning toxins of urine. This is experimentally supported by performing the real urine electrolysis, where the nanospike-covered Ni foam-based catalyst showed a performance similar to that of synthetic urea, offering its industrial value. Other intuition of selecting [MoS4]2– was to provide a ligand-based mechanism for hydrogen evolution half-cell [hydrogen evolution reaction (HER)] to preclude the HER-competing oxygen reduction. Another crucial point of our work is its potential to avoid the mixing of two explosive product gases, that is, H2 and O2.

Hydrogen production coupled with water and organic oxidation based on layered double hydroxides

“…Ni-based LDHs have been reported to display superior urea oxidation activity than noble metals (Pt, Pt-Ir, Rh) in alkaline media. [114][115][116][117][118][119][120][121][122][123][124][125][126] Moreover, the compositional tunability for both laminate cation and interlayer anion of LDHs can be further exploited to improve their urea oxidation performance. It has been reported that the doping of Co cations optimized the electroconductivity and regulated the electronic structure of NiFeCo-LDH, leading to a highly enhanced urea oxidation performance with lower onset potential (0.28 V vs. SCE to reach 10 mA cm -2 ) than NiFe-LDH (0.38 V) in 1 M KOH with 0.33 M urea.…”

Directed Urea‐to‐Nitrite Electrooxidation via Tuning Intermediate Adsorption on Co, Ge Co‐Doped Ni Sites

“…[6][7][8] Nickel (Ni) and its derivatives are the widely reported as "efficient" catalysts for UOR in alkaline. [9][10][11][12][13][14][15][16][17][18][19][20][21] Because of the co-effect of alkaline environment and oxidation potential, the surface Ni component on these Ni-based materials will evolve into Ni oxyhydroxide (NiOOH) via a self-oxidation. [22][23][24][25][26][27] These generated NiOOH serve as active sites to react with urea and degrade it through spontaneous redox.…”

Developing Ecofriendly Chrome-Free Leather Processing-Based Polymer-Intercalated Layered Double Hydroxide Supramolecules

“…As can be seen in Figure a–c, compared with LDHs, the Mg 2p, Al 2p, and Zr 3d spectra of P-LDHs and GEP-LDHs all shifted toward a higher binding energy, but the spin-energy separation of Zr 3d unchanged. This can be interpreted as the replacement of NO 3 – in the interlayer by P and GEP with a lower charge density. , The zeta potential of LDHs, P-LDHs, and GEP-LDHs is 14.8, −23.4, −17.3, 3.8, and 6.1 mV, respectively (Figure d). The zeta potential of P-LDHs and GEP-LDHs is between that of LDHs and P, and LDHs and GEP, respectively, indicating the existence of electrostatic interaction between LDHs and P and GEP. , Moreover, the specific surface area of P-LDHs and GEP-LDHs increases from 113.73 to 146.53 and 136.74 m 2 ·g –1 , and the pore size increases from 8.99 to 25.17 and 21.19 nm, respectively (Figure e,f and Table ).…”