Boosting Urea Electrooxidation Activity of Ni₅P₄ by Vanadium Doping for Urea-Assisted Renewable Energy Conversion Devices

Abstract

The urea oxidation reaction (UOR), a competitive substitute for the oxygen evolution reaction (OER), holds superior potential to meet the upsurge of renewable energy conversion due to low theoretical potential while the sluggish UOR kinetics impede its practical application. In this report, for the first time, we demonstrate that the UOR activity of Ni5P4 is improved via V incorporation. The novel amorphous V-doped Ni5P4 (V10%-Ni5P4) microflower structure with optimized electronic structure was prepared by a solvothermal–phosphorization process. With V atoms involved, the V10%-Ni5P4 microflowers are assembled by much thinner, denser nanosheet units compared with the Ni5P4 counterpart, which endows it with more active sites, enhanced mass transfer, conductivity, and better wettability. The V10%-Ni5P4 microflowers exhibit outstanding UOR activity of 282 mA cm–2 at 1.6 V vs RHE with a low Tafel slope (36.1 mV dec–1). Furthermore, the urea-assisted electrolytic cell only needs 1.44 V to provide 50 mA cm–2 and the urea-assisted rechargeable Zn-Air battery (uZAB) is illustrated to have a higher open-circuit voltage of 1.43 V and possesses a lower potential gap than that Pt/Ir-based uZABs. This report sheds light on the role of vanadium in crystallization and structure optimization and lays the foundation for developing new UOR electrocatalysts.

Regulating Reaction Intermediate Adsorption of Co0.5NiS2–Ni3S2 Nanorods for Efficient Urea Electrolysis

“…Water electrolysis for hydrogen (H 2 ) production powered by green and sustainable sources (e.g., hydro and solar) is widely recognized as a pivotal aspect of the future hydrogen economy. , However, the large kinetic barrier of an anodic oxygen evolution reaction (OER) severely restricts the reaction efficiency. − Even the up-to-the-minute catalysts still require a high overpotential (η 10 ≈ 220–320 mV) due to the restrictive scaling relation of the OER intermediates. , The limitation of high potential can be circumvented by replacing the OER with a thermodynamically more favorable oxidation reaction. − Among them, the urea oxidation reaction (UOR) stands out due to its notably lower theoretical thermodynamic potential (0.37 V RHE ) than that of OER (1.23 V). , Therefore, substituting the UOR for the OER is a promising approach for enabling energy-saving H 2 production while treating wastewater containing urea. Unfortunately, the existing catalysts show unsatisfactory performance in terms of efficiency and durability at large current densities.…”

Urine Treatment in a Stacked Membraneless Direct Urea Fuel Cell with Honeycomb-like Nickel–Molybdenum Bimetal Phosphide as the Anodic Electrocatalyst

“…In the P 2p spectra, the peaks at 129.6 and 133.9 eV were assigned to metal phosphides and P−O bond, respectively (Figure 2F). 35,36 Different molar ratios of Mo and Ni (i.e., 0.25, 0.50, and 0.75) had low effects on the valence states of Ni, Mo, and P in different MoNiP/NF catalysts.…”

Interfacial Coupling of NiPx/MoS2/CC Hybrid Catalysts for Effective Electrocatalytic Oxidation of Urea and Energy‐Saving Hydrogen Evolution

“…In the P 2p, the disappearance of the metal-P peak and PÀ O peak suggest P elements residual in the surface of catalysts could leach into the electrolyte, which further confirm the formation of NiOOH. [13,57] Given the outstanding catalytic HER and UOR activity and durability of NiP x /MoS 2 /CC, the electrolytic cell are assembled and shown in the schematic illustration (Figure 5a) (denoted as NiP x /MoS 2 /CCjjNiP x /MoS 2 /CC). As shown by the orange curve in Figure 5b, when measured in 1 M KOH + 0.33 M Urea, this cell requires low voltages of 1.441 and 1.665 V to reach current densities of 10 and 50 mA cm À 2 , respectively.…”

“…[6][7][8][9][10][11][12] At present, urea oxidation reaction (UOR) has triggered great interests for electrocatalysis because of low theoretical voltage (0.37 V) and purification of urea-rich sewage (stemming from citizen's life, animal husbandry and industry). [13][14][15][16][17] Coupling UOR with HER to produce hydrogen via urea electrolysis was proved a promising method for hydrogen production. [18][19][20] However, the UOR has suffered from sluggish kinetics and complex electron transfer process, and UOR catalyst is mainly composed of rare precious metal catalysts, which is greatly limited to their practical applications in industry.…”