Phase Segregation in Cu_0.5Ni_0.5 Alloy Boosting Urea‐Assisted Hydrogen Production in Alkaline Media

Abstract

Coupling urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is promising for energy‐efficient hydrogen production. However, developing cheap and highly active bifunctional electrocatalysts for overall urea electrolysis remains challenging. In this work, a metastable Cu0.5Ni0.5 alloy is synthesized by a one‐step electrodeposition method. It only requires the potentials of 1.33 and −28 mV to obtain the current density of ±10 mA cm−2 for UOR and HER, respectively. The metastable alloy is considered to be the main reason causing the above excellent performances. In the alkaline medium, the as‐prepared Cu0.5Ni0.5 alloy exhibits good stability for HER; and conversely, NiOOH species can be rapidly formed during the UOR due to the phase segregation of Cu0.5Ni0.5 alloy. In particular, for the energy‐saving hydrogen generation system coupled with HER and UOR, only 1.38 V of voltage is needed at 10 mA cm−2; and at 100 mA cm−2, the voltage decreases by ≈305 mV compared with that of the routine water electrolysis system (HER || OER). Compared with some catalysts reported recently, the Cu0.5Ni0.5 catalyst owns superior electrocatalytic activity and durability. Furthermore, this work provides a simple, mild, and rapid method for designing highly active bifunctional electrocatalysts toward urea‐supporting overall water splitting.

Ni5P4-embedded FeV LDH porous nanosheets for enhancing oxygen evolution and urea oxidation reactions

“…2c, the Ni 2p spectrum consists of Ni 2p 1/2 (874.3 eV) and 2p 3/2 (856.5 eV) along with two satellite peaks. 46,47 Additionally, the Ni 2p spectrum of Ni 5 P 4 @FeV LDH with two peaks at 873.5 and 853.4 eV are assigned to metallic Ni. 48 Compared to the Ni 5 P 4 structure, the Ni 2p peaks of Ni 5 P 4 @FeV LDH have shifted towards a negative binding energy, which indicates that the introduction of Fe and V increased the electron density around the Ni atoms.…”

Insight into the Structure of Mn-NiS2 during Urea Oxidation Using Combined In Situ X-ray Absorption Spectroscopy and Attenuated Total Reflectance Surface-Enhanced Infrared Absorption Spectroscopy

“…In contrast, NiOOH can maintain activity for only about 75 h under the same conditions, illustrating the relevance of Mn doping to the stability of the catalyst during long cycles. In Figure i, our work is compared with a series of catalysts reported in the literature for UOR, demonstrating the preeminent stability of Mn-NiOOH. ,,,,,− …”

Designing bifunctional catalysts for urea electrolysis: progress and perspectives

“…3a and b). 86 Benefiting from the strong electronic interaction between Cu and Ni and the metastable feature, Cu 0.5 Ni 0.5 alloy/NF shows high performance toward both HER and UOR. Especially, the Cu 0.5 Ni 0.5 alloy is more favorable for in situ structure reconstruction during the UOR process and can generate the electroactive NiOOH phase at lower potentials than bare Ni (Fig.…”

“…Alloying is a powerful strategy to raise metals’ intrinsic activity by tuning their electronic properties. Several bimetallic alloys have exhibited favorable performance toward urea electrolysis, such as AuRh, 85 Cu 0.5 Ni 0.5 , 86 and Ni–Mo alloy. 13 Although the noble metal-based AuRh catalyst has an excellent activity for urea electrolysis ( E 100 = 1.47 V), 85 the high price of Au and Rh would limit its practical applications.…”