Constructing Lewis acid-base pairs on S-scheme Al-BiOBr/Bi2O3 heterojunctions for highly efficient photocatalytic nitrogen fixation

Al/Bi-O acid-base pairs were built by spatially selective Al doping in BiOBr/Bi 2 O 3 heterojunction. • The NH 3 yield reached 801.3 μmol g −1 h −1 in pure water, exceeding transition metal doped systems. • Al 3+ polarization activates lattice oxygen as primary Lewis base sites. • In situ KPFM visualizes S scheme charge transfer and the amplified built in field from Al doping. • Oxygen vacancies supply π backdonation channels and enrich electron density of nearby lattice oxygen. Photocatalytic nitrogen fixation has long been constrained by the intrinsic inertness of the N N bond and the severe recombination of photoexcited electron-hole pairs. Here, we construct an aluminum-doped BiOBr/Bi 2 O 3 S-scheme heterojunction in which Al 3 + selectively replaces Bi 3+ sites in the BiOBr lattice, while the Bi 2 O 3 phase retains its inherent crystal structure almost entirely. This asymmetric doping configuration strengthens the internal electric field across the S-scheme interface. The strong polarizing ability of Al 3+ activates nearby lattice oxygen atoms into Lewis base sites and induces the formation of additional oxygen vacancies (Ov), while simultaneously extracting electron density from adjacent Bi centers via Al-O-Bi bridge bonds, thereby enhancing the Lewis acidity of Bi. The resulting Al/Bi-O Lewis acid-base pair activates N 2 through a synergistic push-pull mechanism, in conjunction with the charge modulation induced by the oxygen vacancies. In pure water and in the absence of any sacrificial agent, the optimally designed photocatalyst achieves an NH 3 production rate as high as 801.3 μmol g −1 h −1 under simulated sunlight, surpassing transition-metal-doped analogues. This work establishes a lattice-confined Lewis acid-base pair paradigm, opening a new avenue for designing high-efficiency nitrogen-fixing photocatalysts. Download: Download high-res image (276KB) Download: Download full-size image In pure water and in the absence of any sacrificial agent, the optimally designed photocatalyst Al-BiOBr/Bi 2 O 3 achieves an NH 3 production rate as high as 801.3 μmol g −1 h −1 under simulated sunlight, surpassing transition-metal-doped analogues.