Search

Ethylene glycol electro‐oxidation reaction (EGOR) on nickel‐based hydroxides (Ni(OH)2) represents a promising strategy for generating value‐added chemicals, i.e. formate and glycolate, and coupling water‐electrolytic hydrogen production. The high product selectivity was one of the most significant area of polyols electro‐oxidation process. Yet, developing Ni(OH)2‐based EGOR electrocatalyst with highly selective product remains a challenge due to the unclear cognition about the EGOR mechanism. Herein, Mn‐doped Ni(OH)2 catalysts were utilized to investigate the EGOR mechanism. Experimental and calculation results reveal that the electronic states of eg* band play an important role in the catalytic performance and the product selectivity for EGOR. Broadening the eg* band could effectively enhance the adsorption capacity of glyoxal intermediates. On the other hand, this enhanced adsorption could lead to reduced side reactions associated with glycolate formation, simultaneously promoting the cleavage of C−C bonds. Consequently, the selectivity for formate was notably augmented by these enhancements. This work offers new insights into the regulation of catalyst electronic states for improving polyol electrocatalytic activity and product selectivity. [ABSTRACT FROM AUTHOR]

Understanding the origin of surface reconstruction is crucial for developing highly efficient lattice oxygen oxidation mechanism (LOM) based spinel oxides. Traditionally, the reconstruction has been achieved through electrochemical procedures, such as cyclic voltammetry (CV), linear sweep voltammetry (LSV). In this work, we found that the surface reconstruction in LOM‐based CoFe0.25Al1.75O4 catalyst was an irreversible oxygen redox chemical reaction. And a lower oxygen vacancy formation energy (EO‐V) could benefit the combination of the activated lattice oxygen atoms with adsorbed water molecular. Motivated by this finding, a strategy of phase boundary construction from Co tetrahedral to octahedral was employed to decrease EO‐V in CoFe0.25Al1.75O4. The results showed that as the Co octahedral occupancy ratio rose to 64 %, a 3.5 nm‐thick reconstructed layer formed on the catalyst surface with a 158 mV decrease in overpotential. Further experiments indicated that the coexistence of tetrahedral‐octahedral (O−T) phase would result in lattice mismatch, promoting non‐bonding oxygen states and lowering EO‐V. Then more active lattice oxygen combined with H2O molecules to generate hydroxide ions (OH−), followed by soluble cation leaching, which enhanced the reconstruction process. This work provided new insights into the relationship between the intrinsic structure of pre‐catalysts and surface reconstruction in LOM‐based spinel electrocatalysts. [ABSTRACT FROM AUTHOR]

The anodic methanol oxidation reaction (MOR) plays a crucial role in coupling with the cathodic hydrogen evolution reaction (HER) and enables the sustainable production of the high‐valued formate. Nickel‐based hydroxide (Ni(OH)2) as MOR electrocatalyst has attracted enormous attention. However, the key factor determining the intrinsic catalytic activity remains unknown, which significantly hinders the further development of Ni(OH)2 electrocatalyst. Here, we found that the dx2-y2 ${{d}_{{x}^{2}-{y}^{2}}}$ electronic state within antibonding bands plays a decisive role in the whole MOR process. The onset potential depends on the deprotonation ability (Ni2+ to Ni3+), which was closely related to the band center of dx2-y2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital. The closer of dx2-y2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital to the Fermi level showed the stronger the deprotonation ability. Meanwhile, in the high potential region, the broadening of dx2-y2 ${{d}_{{x}^{2}-{y}^{2}}}$ orbital would facilitate the electron transfer from methanol to catalysts (Ni3+ to Ni2+), further enhancing the catalytic properties. Our work for the first time clarifies the intrinsic relationship between dx2-y2 ${{d}_{{x}^{2}-{y}^{2}}}$ electronic state and the MOR activities, which adds a new layer of understanding to the methanol electrooxidation research scene. [ABSTRACT FROM AUTHOR]