Mechanical force awakens dormant catalyst: Piezocatalytic CO₂ reduction outperforms photocatalysis by over two orders...

Narrow-bandgap semiconductors with non-centrosymmetric structures, while responsive to visible light, often exhibit limited photocatalytic CO₂ reduction performance due to poor quantum efficiency and insufficient thermodynamic driving force. Here, we demonstrate a compelling strategy to repurpose these "dormant" materials as efficient piezocatalysts through mechanical activation. Two-dimensional Cu₂MoS₄ (CMS), a material with weak photocatalytic activity, exhibits CO-dominant piezocatalytic CO₂ reduction under vibration, delivering a CO production rate more than two orders of magnitude higher than that of its photocatalytic counterpart under equivalent nominal power input, together with a substantially improved apparent energy-normalized performance. The piezoelectric properties of CMS were confirmed by piezoelectric force microscopy, piezocurrent measurements, and direct d₃₃ quantification. Finite element analysis indicates that CMS can generate a piezopotential sufficient to drive CO₂ reduction, while density functional theory calculations show that mechanical stress induces a more negative conduction band edge, enhances electron density at sulfur active sites, and lowers the Gibbs free energy barrier for the *COOH-to-*CO step. Under optimized conditions, the CMS nanosheets achieved a CO evolution rate of 594.3 μmol g^-1 h^-1 without cocatalysts. This mechanically driven approach unlocks the catalytic potential of underperforming non-centrosymmetric semiconductors and offers a promising route for sustainable CO₂ conversion through mechanical energy harvesting.