Leveraging Carbon Quantum Dot Spacers as Dual Proton/Electron Boosters to Upgrade TiO2@Polydopamine Photocatalysts for pH‐resilient Conversion of O2 into H2O2

Photocatalytic synthesis of H2O2 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 TiO2 nanoparticles encapsulated by polydopamine (PDA) shells, which delivered stable catalytic activity across a pH range of 1 – 9, exhibiting a photocatalytic generation rate of H2O2 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 H2O2 was benefited from the innovative use of CDs, interspaced between the TiO2 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 O2 reduction to selectively proceed via two‐electron reaction pathway over a wide pH span.