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 (Bi 0 ) nanobridges from layered Bi 2 O 2 CO 3 (BOC) under UV irradiation, which effectively wire BOC with TiO 2 (P25) to form a ternary BOC-Bi 0 -TiO 2 S-scheme heterojunction. Under ultraviolet-visible light or simulated sunlight, the optimized BOC-0.5P25 catalyst achieves a high H 2 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 Bi 0 , accompanied by a slight chemical shift in Ti 2 p and Bi 4 f spectra, consistent with interfacial band bending. Band structure and kinetics analyses elucidate an S-scheme charge transfer mechanism where electrons preferentially flow via Bi 0 into TiO 2 while holes stay on Bi 2 O 2 CO 3 , driven by the built-in field. Isotopic labeling experiments via Gas Chromatography-Mass Spectrometry (GC–MS) isotopologues (CH x D 4-x in D 2 O/MeOH) together with online Differential Electrochemical Mass Spectrometry (DEMS) signals confirm that water contributes to both H 2 production and methanol oxidative reforming (partially to CH 4 ). 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.