Leveraging Carbon Quantum Dot Spacers as Dual Proton/Electron Boosters to Upgrade TiO ₂ @Polydopamine Photocatalysts for pH‐Resilient Conversion of O ₂ into H ₂ O ₂

Abstract Photocatalytic synthesis of H 2 O 2 is a proton‐coupled electron transfer (PCET) process, which is generally jeopardized by the kinetic mismatch between photogenerated electron transfer and proton supply. To address the challenge, here we proposed a new core–shell design of nanocomposite catalysts comprising of carbon quantum dot (CD)‐topped TiO 2 nanoparticles encapsulated by polydopamine (PDA) shells, which delivered stable catalytic activity across a pH range of 1–9, exhibiting a photocatalytic generation rate of H 2 O 2 that reached 18.14 mmol g −1 h −1 in methanol and 8.66 mmol g −1 h −1 in water. This extraordinary, pH‐tolerant photocatalytic generation of H 2 O 2 was benefited from the innovative use of CDs, interspaced between the TiO 2 cores and PDA shells, not only as a reservoir of protons to buffer the local acidic microenvironment but also as a proton/electron dual booster to sustain an excellent kinetic match between the proton and photogenerated electron transfer, thus enabling the O 2 reduction to selectively proceed via two‐electron reaction pathway over a wide pH span.