Modulation Strategies for the Preparation of High‐Performance Catalysts for Urea Oxidation Reaction and Their Applications

Abstract

Compared with the traditional electrolysis of water to produce hydrogen, urea‐assisted electrolysis of water to produce hydrogen has significant advantages and has received extensive attention from researchers. Unfortunately, urea oxidation reaction (UOR) involves a complex six‐electron transfer process leading to high overpotential, which forces researchers to develop high‐performance UOR catalysts to drive the development of urea‐assisted water splitting. Based on the UOR mechanism and extensive literature research, this review summarizes the strategies for preparing highly efficient UOR catalysts. First, the UOR mechanism is introduced and the characteristics of excellent UOR catalysts are pointed out. Aiming at this, the following modulation strategies are proposed to improve the catalytic performance based on summarizing various literature: 1) Accelerating the active phase formation to reduce initial potential; 2) Creating double active sites to trigger a new UOR mechanism; 3) Accelerating urea adsorption and promoting C─N bond cleavage to ensure the effective conduct of UOR; 4) Promoting the desorption of CO2 to improve stability and prevent catalyst poisoning; 5) Promoting electron transfer to overcome the inherent slow dynamics of UOR; 6) Increasing active sites or active surface area. Then, the application of UOR in electrochemical devices is summarized. Finally, the current deficiencies and future directions are discussed.

Ni3Se4/Fe(PO3)2/NF composites as high-efficiency electrocatalysts with a low overpotential for the oxygen evolution reaction

“…43 However, low crystalline or amorphous materials have the problems of low conductivity and insufficient stability in harsh corrosive environments, which greatly limits the charge transfer and their catalytic performance. 44 Therefore, coordinating the advantages of low crystalline/amorphous structure and high crystalline structure, optimizing the electronic structures, increasing the number and intrinsic activity of active sites is the key to achieving high-performance OER. 45…”

Co/Co3O4 Heterojunctions Encased in Porous N-Doped Carbon Nanocapsules for High-Performance Cathode of Rechargeable Zinc–Air Batteries

“…6,7 Platinum−carbon catalyst (Pt/C) is currently considered to have high ORR catalytic performance, and iridium oxide (IrO 2 )/ruthenium oxide (RuO 2 ) catalysts are considered to own superior OER catalytic performance. 8,9 Unfortunately, noble-metal-based catalysts are expensive and challenging to use as both the OER and the ORR bifunctional catalysts. As a result, although the procedure is difficult, it is critical to produce affordable bifunctional catalysts with high ORR and OER catalytic capabilities to substitute noble metal catalysts for ZABs.…”

“…The issue of energy scarcity in human society can be resolved by the deployment of green rechargeable energy storage devices, which can also lessen the impact of the oil crisis on local conflicts. − Rechargeable zinc–air batteries (ZABs) are becoming more and more popular because of their low cost, safety, and high energy density (1218 W h kg –1 ). , However, the slow oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) at the cathode prevent ZABs from being widely commercialized. , Platinum–carbon catalyst (Pt/C) is currently considered to have high ORR catalytic performance, and iridium oxide (IrO 2 )/ruthenium oxide (RuO 2 ) catalysts are considered to own superior OER catalytic performance. , Unfortunately, noble-metal-based catalysts are expensive and challenging to use as both the OER and the ORR bifunctional catalysts. As a result, although the procedure is difficult, it is critical to produce affordable bifunctional catalysts with high ORR and OER catalytic capabilities to substitute noble metal catalysts for ZABs. − …”

Built-in electric field induced interfacial charge distributions of Ni2P/NiSe2 heterojunction for urea-assisted hydrogen evolution reaction

“…Compared to the OER with its excessive energy consumption, an organic oxidation reaction that is more convenient in terms of thermodynamics should be selected as a substitute. As an example, the oxidation reaction of urea molecules, the UOR (0.37 V vs. RHE), which has a lower thermodynamic potential, can be utilized instead of the conventional OER (1.23 V vs. RHE), 11–15 resulting in a significant increase in energy conversion efficiency, and thus becoming a promising alternative to the OER for sustainable hydrogen power generation. Nevertheless, the most studied catalysts to date are generally monofunctional catalysts, which are only active for either the HER or the UOR.…”