Self‐supporting Nickel Phosphide/ Hydroxides Hybrid Nanosheet Array as Superior Bifunctional Electrode for Urea‐Assisted Hydrogen Production

Abstract

Urea oxidation reaction (UOR) is an important strategy to synergistically realize energy‐saving hydrogen evolution reaction (HER) and urea‐rich wastewater purification by replacing water oxidation in water electrolysis. However, the efficient realization of integral urea electrolysis remains challenging. Herein, a self‐supporting Ni2P−Ni(OH)2 hybrid nanosheet array on nickel foam (Ni2P@Ni(OH)2/NF) is designed by a simple hydrothermal accompanied by electrodeposition strategy, representing a new class of bifunctional electrodes for urea‐assisted water electrolysis. The Ni2P@Ni(OH)2/NF reaches the current density of 100 mA cm−2 at potentials of −0.16 V and 1.388 V, along with small Tafel slopes of 69 mV dec−1 and 33 mV dec−1 for HER/UOR, respectively. For the HER||UOR coupled system, the constructed electrolyzer only needs 1.38 V to realize the current density of 100 mA cm−2 under 80 °C. The superior bifunctional activity of the Ni2P@Ni(OH)2/NF electrode is ascribed to the combined merits of the Ni2P@Ni(OH)2 heterostructure, enriching the catalytic active sites and offering a faster charge transfer process for electrolysis. Our work provides important insights into the design of highly active bifunctional catalysts from the perspective of overall water electrolysis.

Designing bifunctional catalysts for urea electrolysis: progress and perspectives

“…127 metal nanoparticles, and metal oxides/sulfides/phosphides/ nitrides have been introduced. 68,[121][122][123][124] Carbon materials like multiwalled carbon nanotubes (MWCNTs) 122 and fullerene quantum dots 125 can help to compensate the conductivity of LDHs, and importantly, fullerene quantum dots are suggested to precisely tune the electronic properties of CoNi-LDH and thereby favor reaction intermediate adsorption during urea electrolysis. The coupling of metal-bearing components with LDHs can also provide active sites and optimize the catalysts' electronic properties.…”

The synthesis of γ-MnOOH nanorods as an efficient electrocatalyst for urea oxidation

“…The polarization curves were presented without iR compensation. The overpotential of UOR was calculated through the formula as follows: overpotential = Em-Et, where Em and Et values are the measured potential vs. RHE and the theoretical value of urea oxidation reaction, which is 0.37 V. [16]…”

The In Situ Construction of NiFeS on Stainless Steel Mesh as an Efficient Electrocatalyst for UOR

“…Among them, a commonly used high-purity hydrogen production process was hydrogen production based on electrocatalytic water splitting, which couples the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). 4,5 However, traditional water electrolysis faces challenges due to the relatively high overpotential (1.23 V) and slow reaction kinetics, involving a 4e-transfer during the anode OER process, resulting in high energy consumption. 6,7 The hybrid electrolysis method has emerged at a historic moment, employing a more favorable anodic oxidation reaction to replace the OER process.…”