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[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]

[Display omitted] • Ti 3 C 2 /Pd was designed for efficient catalytic transfer hydrogenation of nitrobenzene. • Experimental and DFT theoretical studies unravel unique catalytic mechanism. • Electron transfer at Ti 3 C 2 /Pd interfaces changes Pd electron configure (4 d 10 → 4 d 10-x). • Electron-deficient Pd boosts formic acid dissociation for atomic H* production. • Ti 3 C 2 /Pd chemisorbs active H* and inhibits undesirable H 2 evolution. Catalytic transfer hydrogenation (CTH) with formic acid attracts much interest in catalysis, but the sluggish H* production and undesirable H 2 evolution reaction (HER) limit its practical applications. Herein we anchored Pd nanoparticles (NPs) on layered Ti 3 C 2 MXene for efficient and selective CTH of nitrobenzene in the presence of formic acid. Some electrons in Pd NPs transferred to Ti 3 C 2 MXene upon formation of Ti 3 C 2 /Pd nanohybrids, as confirmed by XPS and DFT simulations. The electron transfer changed Pd valance electron configuration from 4 d 10 to 4 d 10-x. Such electron-deficient Pd NPs tuned reaction pathway and promoted formic acid dissociation, both of which favored the production of active H* atoms, i.e., the exact reductant for CTH. Compared with Pd NPs, Ti 3 C 2 /Pd showed stronger adsorption of H* and therefore inhibited the occurrence of HER (2H*→H 2). Owing to favorable H* production and HER inhibition, Ti 3 C 2 /Pd (15 wt% Pd) showed enhanced nitrobenzene CTH performance with turnover frequency of 351.7 h−1 and 99% aniline selectivity, outperforming most of current catalysts. Our work might inspire designing more advanced CTH catalysts by tuning their valance electron configurations with 2D MXene materials. [ABSTRACT FROM AUTHOR]

Internal electric field (IEF) at heterojunction interfaces can separate photoexcited charge carriers and promote photocatalytic performance. Here we have modified WO 3 nanoplates with carbon dots (CDs) and constructed an interfacial IEF directing from CDs to WO 3 with assistance of their remarkably different work functions. Such electric field drove photoexcited electrons to transport towards CDs and retained photoexcited holes to stay at WO 3 , achieving electron/hole spatial separation. H 2 O preferred chemisorption on the five-coordinated W atoms of WO 3 with an elongated H-O bond and bent H-O-H angle, which allowed the activation of H 2 O and favorable production of ·OH radicals. The WO 3 /CDs (WC1) showed a superior photocatalytic activity for visible-light photooxidation of HCHO and CH 3 COCH 3 with CO 2 production rate of 411 and 188 μmol g–1 h–1, respectively, outperforming most of WO 3 -based photocatalysts. The enhanced photocatalytic performance correlated with the IEF-induced charge separation, favorable ·OH production and VOCs chemisorption. Our work confirms the role of CDs cocatalyst in the photocatalytic oxidation of VOCs, which will inspire enthusiasm to develop more advanced heterojunction photocatalysts involving carbon nanomaterials. [Display omitted] • Carbon dots-modified WO 3 nanoplates were designed for VOCs photodegradation. • Work function difference enables electron transfer from CDs to WO 3 upon contact. • Internal electric field drives charge separation evidenced by in-situ XPS and DFT simulations. • WO 3 chemisorbs and activates water with preferential hydroxyl radicals production. • Water activation and internal electric field account for superior photocatalytic performance. [ABSTRACT FROM AUTHOR]