MXene-Mediated Electronic State Engineering of Nickel Hydroxide for Efficient Piezo-Catalytic Hydrogen Peroxide Synthesis

The piezo-catalytic synthesis of hydrogen peroxide (H₂O₂) offers a sustainable alternative to the traditional anthraquinone process by enhancing both the water oxidation reaction (WOR) and oxygen reduction reaction (ORR). However, conventional high-dielectric-constant piezoelectric materials, despite their superior piezoelectric responses, generally feature wide band gaps, low electrical conductivity, and a limited number of active sites─catalytically unfavorable characteristics that restrict their piezocatalytic efficiency. To address this, we developed a 2D Ni(OH)₂-Ti₃C₂T_<i>x</i> MXene composite for efficient H₂O₂ production in pure water. The Ti₃C₂T_<i>x</i> MXene modifies the electronic states of Ni(OH)₂, enhancing its deprotonation ability (Ni²⁺ to Ni³⁺) and creating hypervalent nickel active sites that boost H₂O₂ synthesis. Theoretical and experimental studies confirm that H₂O₂ generation occurs through combined WOR and ORR pathways, with ORR being dominant. The hierarchical 2D nanosheet structure facilitates crystal deformation under mechanical stress, amplifying the piezoelectric effect and reducing the energy input required for redox reactions. As a result, the Ni(OH)₂-Ti₃C₂T_<i>x</i> composite achieves an impressive H₂O₂ yield of 351.1 μmol·g^-1·h^-1. This work provides a novel design strategy for high-performance piezo-catalysts in sustainable H₂O₂ production.