Optimizing electronic states of Pd/WO3 nanofibers for enhanced catalytic reduction of hexavalent chromium with formic acid.

[Display omitted] • Pd/WO 3 was designed for catalyzing the reduction of toxic pollutants. • DFT and XPS unravel a unique catalytic mechanism for the Cr(VI) reduction by formic acid. • Electron transfer at WO 3 /Pd interfaces optimizes Pd electronic states and upshifts d -band center. • Electron-deficient Pd boosts formic acid dissociation for efficient H* production. • Pd/WO 3 surpasses most Pd-based catalysts for Cr(VI) reduction with high TOF of 62.12 min−1. Through theoretical calculations, we show that integrating Pd with WO 3 nanomaterials can trigger the interfacial electron transfer from Pd to WO 3 , thus upshifting the d -band center (ε d) of Pd to optimize toxic hexavalent chromium (Cr(VI)) reduction. The elevated ε d can derive stronger chemisorption capability toward crucial formic acid molecules, notably lowering the thermodynamic energy barrier and speeding up the kinetics process. In order to realize this concept, we synthesized unique Pd/WO 3 nanofibers by loading Pd nanoparticles onto electrospun WO 3 nanofibers through an in situ photodeposition technique. Extensive structural, morphological, and X-ray photoelectron spectrometer (XPS) characterizations confirm the successful formation of the above nanofibers. As anticipated, the as-designed Pd/WO 3 nanofibers exhibit enhanced catalytic performance in the Cr(VI) reduction with a high turnover frequency (TOF) value of 62.12 min−1, surpassing a series of reported Pd-based catalysts. Such nanofibrous WO 3 -induced electronic modification of Pd with a high specific area leads to catalytic enhancement, providing a novel model for catalyst design. [ABSTRACT FROM AUTHOR]