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.