Crystal-structure dependent reaction pathways in photocatalytic formaldehyde mineralization on BiPO4

Abstract

Formaldehyde as significant environmental hazard in air seriously harm the environment and human health. Although photocatalysis has demonstrated the possibility for HCHO degradation, it has long been limited by unsatisfied degradation efficiency and the unclear reaction mechanism. Here, we confirm that surface atomic arrangement of BiPO4 plays a critical role in photooxidation of HCHO via modulating the reaction pathway, offering 2.63 times enhancement of HCHO degradation efficiency. We dissect the processes in the photocatalytic reaction by DFT calculation, ROS monitoring, and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) investigation. Specifically, we reveal that the controlling surface atomic arrangement could modulate adsorption model from single-point to bridging, and promote activation of small molecules. Concurrently, the active surface dependent on crystal structure facilitates the efficient transformation of intermediates (HCOOH*) (reducing energy barrier from 0.41 to −0.35 eV), producing final-product (H2CO3, ∆G = −0.35 eV) while suppressing toxic by-product (CO, ∆G = 0.32 eV), which contributes to the sustained deep mineralization of HCHO with enhancement by 61.4%. The findings are crucial as they provide crystal-structure related insights into the design of efficient catalysts for photocatalytic HCHO degradation. Ultimately, current molecular understanding should unlock the solar-driven catalytic pathways for other oxidation reactions.