Constructing Ultrathin In-Plane Phase-Junctions in Nickel Hydroxide Nanosheets for Selective Electro-Oxidation of Methanol to Formate Coupled with Hydrogen Evolution

Developing highly efficient nickel-based electrocatalysts toward the methanol oxidation reaction (MOR) is of considerable significance for energy conversion and chemical synthesis, yet it is still a challenging issue. Herein, we developed a facile <i>in situ</i> phase transformation strategy to construct in-plane phase-junctions in ultrathin α/β-Ni(OH)₂ nanosheets as a high-performance electrocatalyst for the MOR. Specially, the role of in-plane phase-junctions played in the MOR process was deeply clarified through the combination of experimental and theoretical studies. <i>In situ</i> Fourier transform infrared spectroscopy indicates that the MOR process concurrently involves the formate-forming and CO-forming pathways over the α/β-Ni(OH)₂ electrode. <i>In situ</i> Raman spectroscopy reveals that NiOOH species originating from the dehydrogenation of Ni(OH)₂ are electroactive sites for the MOR. Density functional theory calculations disclose that the construction of in-plane phase-junctions can not only improve the charge-transfer capacity, but also endow Ni(OH)₂ with enhanced ability to generate NiOOH species and adsorb methanol molecules, enabling more advantageous kinetics for the MOR. Therefore, the prepared α/β-Ni(OH)₂ nanosheets show excellent electrocatalytic MOR activity and stability, exhibiting high performance for formate production up to 94.1% faradaic efficiency at 0.45 V vs Ag/AgCl. This work highlights the crucial efficacy of the phase-junction in the electrochemical MOR process for biomass valorization.