Oxygen vacancy modulation via vanadium doping defect engineering in heteropoly acids: A strategy for high-performance low O/S ratio oxidative desulfurization

Oxygen vacancies (Ov) are crucial for modulating electronic structures and catalytic properties. Herein, a vacancy-rich HEDP-MoV heteropoly acid catalyst was synthesized via one-pot hydrothermal method by vanadium substituting molybdenum in phosphomolybdic acid with HEDP as support, focusing on Ov’s role in enhancing oxidative desulfurization (ODS) efficiency. XPS and EPR analyses showed vanadium incorporation (less electronegative than Mo) modulated Mo 5+ /Mo 6+ ratio and linearly increased Ov content from 28.65% (HEDP-Mo 10 V 2 ) to 41.81% (HEDP-Mo 7 V 5 ), promoting electron transfer and activity. The HEDP-MoV system exhibited superior H 2 O 2 activation and ·OH generation, with DBT desulfurization rate 41.6% higher than unsubstituted HEDP-Mo. The optimized HEDP-Mo 7 V 5 achieved 99.1% DBT desulfurization at O/S=3 and 30   o C (milder than most reported PMoV catalysts requiring O/S≥5) and retained 98% activity after 10 cycles. Radical quenching and EPR confirmed ·OH as dominant reactive species, while DFT verified H 2 O 2 dissociation thermodynamics. This study highlights vanadium substitution as an effective defect engineering strategy for HPA catalysts and provides a scalable pathway for mild-condition ultra-deep diesel ODS.