Construction of Frustrated Lewis Pair Sites in CeO2-C/BiVO4 for Photoelectrochemical Nitrate Reduction.

Photoelectrochemical nitrate reduction reaction (PEC NIRR) could convert the harmful pollutant nitrate (NO3-) to high-value-added ammonia (NH3) under mild conditions. However, the catalysts are currently hindered by the low catalytic activity and slow kinetics. Here, we reported a heterostructure composed of CeO2 and BiVO4, and the "frustrated Lewis pairs (FLPs)" concept was introduced for understanding the role of Lewis acids and Lewis bases on PEC NIRR. The electron density difference maps indicated that FLPs were significantly active for the adsorption and activation of NO3-. Furthermore, carbon (C) improved the carrier transport ability and kinetics, contributing to the NH3 yield of 21.81 µg h-1 cm-2. The conversion process of NO3- to NH3 was tracked by 15NO3- and 14NO3- isotopic labeling. Therefore, this study demonstrated the potential of CeO2-C/BiVO4 for efficient PEC NIRR and provided a unique mechanism for the adsorption and activation of NO3- over FLPs.

ZIF-8 derived ZnO/TiO2 heterostructure with rich oxygen vacancies for promoting photoelectrochemical water splitting.

Due to the serious recombination of electron-hole and weak photoresponse ability, achieving highly efficient photoelectrochemical (PEC) water splitting activity for TiO2 photoelectrode has become a key issue. In this paper, we reported a new method for preparing ZnO/TiO2 photoelectrodes by electrostatic adsorption from zeolitic imidazolate framework-8 (ZIF-8) as the precursor. ZIF-8 was combined with TiO2 nanorods (NRs) through electrostatic interaction and then calcined to obtain ZnO/TiO2 heterojunction photoelectrodes with abundant oxygen vacancies (Ovac). The introduced ZnO with Ovac provides a large number of active sites which enhanced the electrical conductivity and charges separation of ZnO/TiO2 photoelectrode. The optimal photocurrent density of ZnO/TiO2 photoelectrodes at 1.23 V versus (vs.) reversible hydrogen electrode (RHE) under illumination (100 mW/cm2) has reached 1.76 mA/cm2, almost 2.75 times that of the pure TiO2. Meanwhile, the incident photon-to-electron conversion efficiency (IPCE) of the best photoelectrode has increased to 58.2% at 390 nm, the charge injection (ηinjection) and separation (ηseparation) efficiency have reached to 93.53% and 51.62% (1.23 V vs. RHE), respectively.