Bimetallic Pd-In alloy supported on TiO₂ nanosheets breaks the rate-limiting step for ultrafast photocatalytic denitrification

Abstract

Herein, the bimetallic Pd₃In₁ alloy were deposited onto the crystal facet engineered TiO₂ nanosheet (NS) via one-step photoreduction (Pd₃In₁/TiO₂-NS) for selective conversion of nitrate (NO₃⁻) to N₂. Bimetallic Pd₃In₁ provides higher affinity sites to bind NO₃⁻ and significantly reduces the energy barrier of the rate-limiting step (NO₃* + e⁻ → NO₂*), which is the key for the ultra-fast NO₃⁻ reduction kinetics. More importantly, the synergistic effect of Pd and In not only suppresses the hydrogen evolution reaction resulting in high efficiency utilization of photogenerated electrons, but also promotes the selective conversion of nitrite (NO₂⁻) to N₂. Consequently, Pd₃In₁/TiO₂-NS exhibits 100 % NO₃⁻ conversion and 90 % N₂ selectivity within 20 min in six cycles. One order of magnitude improvement on the NO₃⁻ reduction kinetic constants of Pd₃In₁/TiO₂-NS (0.254 min⁻¹) is achieved compared with pristine TiO₂-NS and monometallic loaded ones. This work provides new insights into the rational construction of bimetallic alloy cocatalysts for high-efficiency photocatalytic denitrification.