Unconventional Phase Synergies with Doping Engineering Over Ni Electrocatalyst Featuring Regulated Electronic State for Accelerated Urea Oxidation

Abstract

Exploring high‐performing Ni‐based electrocatalysts for the urea oxidation reaction (UOR) is crucial for developing urea‐related energy technologies yet remains a daunting challenge. In this study, a synergistic anomalous hcp phase and heteroatom doping engineering over metallic Ni are found to enhance the UOR. A metal‐organic framework‐mediated approach is proposed to construct Ni nanoparticles (NPs) with designated crystal phase embedded in N‐doped carbon (fcc‐Ni/NC and hcp‐Ni/NC). Significant crystal phase‐dependent catalytic activity for the UOR is observed; hcp‐Ni/NC, featuring unusual hcp phase, outperforms fcc‐Ni/NC with conventional fcc phase. Moreover, incorporating foreign Mn species in hcp‐Ni/NC can further dramatically promote UOR, making it among the best UOR catalysts reported to date. From experimental results and DFT calculations, the specific nanoarchitecture, involving an anomalous hcp phase together with Mn doping engineering, endows hcp‐MnNi/NC with abundant exposed active sites, facile charge transfer, and more significantly, optimized electronic state, giving rise to enriched Ni3+ active species and oxygen vacancies on the catalyst surface during electrocatalysis. These features collectively contribute to the enhanced UOR activity. This work highlights a potent design strategy to develop advanced catalysts with regulated electronic state through synergistic crystal phase and doping engineering.

Recent Progress on Phase Engineering of Nanomaterials

“…For example, a series of Ni-based nanoparticles encapsulated in N-doped carbon (NC) substrate with different phases, namely fcc-Ni/NC, hcp-Ni/NC, and hcp-MnNi/NC, has been synthesized as catalysts toward the UOR. 1096 It was found that the metallic Ni with unconventional hcp phase was more favorable for catalyzing the UOR with respect to fcc-Ni (Figure 112g). In the meantime, the doping of foreign Mn species further regulated the electronic structure of Ni sites, leading to optimized adsorption/desorption behaviors of crucial reaction intermediates during the UOR process, thereby substantially improving the intrinsic catalytic activity.…”

“…(i) ECSA-normalized UOR polarization curves of fcc -Ni/NC, hcp -Ni/NC, and hcp -MnNi/NC samples. Reproduced with permission from ref . Copyright 2023 Wiley-VCH.…”

“…To overcome this challenge, various strategies, including PEN, have been utilized to prepare highly efficient UOR catalysts. For example, a series of Ni-based nanoparticles encapsulated in N-doped carbon (NC) substrate with different phases, namely fcc -Ni/NC, hcp -Ni/NC, and hcp -MnNi/NC, has been synthesized as catalysts toward the UOR . It was found that the metallic Ni with unconventional hcp phase was more favorable for catalyzing the UOR with respect to fcc -Ni (Figure g).…”

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

“…Tian et al controlled the crystal structure of Ni metal to prepare metal Ni with an abnormal hcp phase, which is superior to the fcc phase metal Ni reported in many reports. [ 248 ] Therefore, we encourage researchers to regulate the crystal structure of Ni‐based materials to obtain novel materials with better UOR activity. In addition, nano glass (NG) and high‐entropy compounds provide new ideas for regulating the functional properties of catalysts and have good UOR activity.…”

Multiscale Structural Engineering of a Multilayered Nanoarray Electrode Realizing Boosted and Sustained Oxygen Evolution Catalysis in Seawater Electrolysis

“…Among various cost-competitive transition-metal-based materials explored for the OER in freshwater electrolysis, cobalt selenides, possessing varied polymorphs, have drawn huge research attention. − In particular, the typical nonstoichiometric cobalt selenide, Co 0.85 Se, has recently aroused intensive interest as a result of its special electronic structure, good corrosion resistance, together with intrinsic half-metallic nature for facile electron transfer, which is in striking contrast with other cobalt selenide polymorphs in semiconducting nature (e.g., CoSe and Co 9 Se 8 ). − The above characteristics render Co 0.85 Se to be a promising candidate for expediting seawater oxidation under harsh conditions, whereas further enhancing both catalytic activity and anticorrosion behavior of Co 0.85 Se is a prerequisite to meet strict requirements for selective OER in seawater electrolysis. The aliovalent doping has been well-accepted as a feasible strategy to tailor the intrinsic catalytic capability via regulating surface electronic configuration. − Specially, doping of high-valence-state metal species (e.g., Mo, W, Cr, and V) has been demonstrated to be a powerful protocol to modulate the electron density. , Beyond that, interface engineering by integrating different components into one hybrid can not only inherit advantages of each moiety but also afford populated active centers at the interface, and meanwhile, present elevated inherent catalytic ability via the strong interfacial coupling effect. − …”