Piezo‐catalysis Mechanism Elucidation by Tracking Oxygen Reduction to Hydrogen Peroxide with In‐situ EPR Spectroscopy

For piezoelectric catalysis, the catalytic mechanism is a topic of great controversy, with debates centered around whether it belongs to the energy band theory of photocatalysis or the screening charge effect of electrochemical catalysis. Due to the formation of different intermediate active‐species during two‐electron oxygen reduction reaction (ORR) via electro‐ and photo‐catalysis, the key to solving this problem is precisely monitoring the active species involved in ORR during electro‐, photo‐, and piezo‐catalysis under identical condition. Here, a semiconductor material, BiOBr with abundant oxygen vacancies (BOB‐OV) was found remarkable catalytic activity in H2O2 production by all three catalytic methods. By employing in‐situ electron paramagnetic resonance (EPR) spectroscopy, the H2O2 evolution pathway through piezo‐catalysis over BOB‐OV was monitored, which showed a similar reaction pathway to that observed in photo‐catalytic process. This finding represents solid evidence supporting the notion that piezo‐catalytic mechanism of ORR is more inclined towards photo‐catalysis rather than electro‐catalysis. Significantly, this exploratory conclusion provides insight to deepen our understanding of piezo‐catalysis.