Laponite nanoclay as a solid-state charge transfer mediator for piezocatalytic hydrogen evolution

Abstract

Nowadays, the integration of light and mechanical energy in photopiezocatalysis has attracted growing attention for enhancing catalytic efficiency through synergistic electron-hole separation. However, the limited charge separation efficiency and structural stability of conventional piezocatalysts remain critical challenges. In this work, ZnO nanoparticles were successfully synthesized at different mass ratios loading onto Laponite clay to construct a novel Laponite/ZnO composite, aiming to enhance piezocatalytic hydrogen evolution reaction (HER) performance. Notably, while pristine Laponite showed no piezocatalytic HER activity, however, the 15% Laponite/ZnO composite (LZO15) exhibited significantly enhanced performance, with nearly 4-fold and 2.5-fold increases in piezocatalytic and photopiezocatalytic hydrogen evolution, respectively, compared to bare ZnO. LZO15 achieved a mechanical-to-hydrogen (MTH) efficiency of 0.41%, indicating its superior ability to harvest mechanical energy and convert it into chemical energy via piezocatalytic processes. The formation of interfacial Si-O-Zn bonds, originating from the interaction between ZnO and the Si-OH groups present on the Laponite matrix, serves as an efficient electron transfer pathway, significantly promoting charge separation and enhancing overall catalytic activity. These Si-O-Zn bonds create a fast transfer channel for piezoelectric polarization and photo-assisted induced charges, effectively reducing charge carrier recombination and accelerating interfacial charge migration. The proofing of photo/piezocatalytic hydrogen evolution performance of the Laponite/ZnO composite was also systematically investigated using electronic impedance spectroscopy (EIS), Mott-Schottky analysis, and chronoamperometry, providing clear evidence of its enhanced electron-hole separation and catalytic efficiency.