From Lying to Standing: Anchoring Naphthoquinone via Pd─S Bonds on Pd Nanoclusters to Suppress Over‐Hydrogenation for Mild H ₂ O ₂ Synthesis

ABSTRACT

The industrial anthraquinone (AQ) process for H ₂ O ₂ production is limited by undesired deep hydrogenation of quinone working compound, promoted by cofacial adsorption of its aromatic π‐system on Pd surfaces. Here, we report a Pd─S anchoring strategy that constrains a dithiolated naphthoquinone ligand (SNQ), whose quinone moiety serves as a simplified structural model of AQ, in a standing configuration on low‐valent Pd nanoclusters. This directional coordination minimizes direct contact between the aromatic framework and Pd while retaining access of the carbonyl groups to activated hydrogen. Supported on XC‐72 affords a catalyst that produces H ₂ O ₂ through sequential H ₂ hydrogenation and air oxidation under mild conditions (0.2 MPa H ₂ , 30°C), achieving 300 mmol g _Pd ⁻¹  h ⁻¹ and maintaining its initial activity over eight cycles. X‐ ray absorption spectroscopy supports the coexistence of Pd─Pd and Pd─S coordination, whereas in situ diffuse reflectance infrared Fourier transform spectroscopy reveals a reversible quinone/hydroquinone‐type redox cycle. Density functional theory calculations further identify carbonyl hydrogenation as energetically favored over aromatic‐ring hydrogenation. The Pd─S interface thus electronically promotes H ₂ activation and geometrically restricts the quinone π‐system, spatially decoupling H ₂ activation from aromatic‐ring adsorption and enabling selective, durable quinone‐mediated H ₂ O ₂ synthesis.