Photoderived Bi0 nanobridge enabling an S-scheme Bi2O2CO3-Bi0-TiO2 heterojunction for efficient photocatalytic water splitting and methanol reforming.

Constructing strongly coupled S-scheme heterojunctions without sacrificing redox capability remains a central challenge in photocatalytic water splitting. Herein, we report the in situ photogeneration of metallic Bi (Bi0) nanobridges from layered Bi2O2CO3 (BOC) under UV irradiation, which effectively wire BOC with TiO2 (P25) to form a ternary BOC-Bi0-TiO2 S-scheme heterojunction. Under ultraviolet-visible light or simulated sunlight, the optimized BOC-0.5P25 catalyst achieves a high H2 evolution rate of ∼5.8 mmol·g-1·h-1, which further increases by ∼24 % (to ∼7.2 mmol·g-1·h-1) after light-activated cycling. The apparent quantum efficiency (AQE) reaches 2.45 % at 380 nm. Structural characterizations confirm the light-induced formation of Bi0, accompanied by a slight chemical shift in Ti 2p and Bi 4f spectra, consistent with interfacial band bending. Band structure and kinetics analyses elucidate an S-scheme charge transfer mechanism where electrons preferentially flow via Bi0 into TiO2 while holes stay on Bi2O2CO3, driven by the built-in field. Isotopic labeling experiments via Gas Chromatography-Mass Spectrometry (GC-MS) isotopologues (CHxD4-x in D2O/MeOH) together with online Differential Electrochemical Mass Spectrometry (DEMS) signals confirm that water contributes to both H2 production and methanol oxidative reforming (partially to CH4). The concept of light-triggered, in-situ mediator activation provides a practical route for photocatalytic water reduction coupled with methanol oxidative reforming under unbiased and noble-metal-free conditions through engineering tightly coupled S-scheme interfaces.