ABSTRACT
The hydrogen (H2) evolution rates of photocatalysts suffer from weak oxidation and reduction ability and low photogenerated charge carrier separation efficiency. Herein, by combining band-gap structure optimization and vacancy modulation through a one-step hydrothermal method, In2O3 containing oxygen vacancy (Ov/In2O3) is simply introduced into In2S3 to promote photocatalytic hydrogen evolution. Specifically, the change in the sulfur source ratio can induce the coexistence of Ov/In2O3 and In2S3 in a high-temperature hydrothermal process. Under light irradiation, In2S3@Ov/In2O3-0.1 nanosheets hold a remarkable average H2 evolution rate up to 4.04 mmol g-1 h-1, which is 32.14, 11.91, and 2.25-fold better than those of pristine In2S3, In2S3@Ov/In2O3-0.02, and In2S3@Ov/In2O3-0.25 nanosheets, respectively. The ultraviolet-visible (UV-vis) diffuse reflectance and photoluminescence (PL) spectra reveal that the formation of Ov/In2O3 in In2S3 optimizes the band-gap structure and accelerates the migration of the photogenerated charge carrier of In2S3@Ov/In2O3-x nanosheets, respectively. Both the enhancement of oxidation and reduction ability and photogenerated charge carrier separation ability are responsible for the remarkable improvement in photocatalytic H2 evolution performance. This work provides a new strategy to prepare a composite of metal sulfide and metal oxide through a one-step hydrothermal method.
ABSTRACT
A general method for the direct synthesis of highly homogeneous and dense polymerized carbon nitride (PCN) nanosheet films on F: SnO2 (FTO) is developed. Detailed photoelectrochemical (PEC) water-splitting studies reveal that the as-synthesized PCN films exhibit outstanding performance as photoanode for PEC water-splitting. The optimal PCN photoanode exhibits excellent photocurrent density of 650 µA cm-2 , and monochromatic incident photon-to-electron conversion efficiency (IPCE) value up to 30.55% (λ = 400 nm) and 25.97% (λ = 420 nm) at 1.23 VRHE in 0.1 m KOH electrolyte. More importantly, the PCN photoanode has an excellent hole extraction efficiency of up to 70 ± 3% due to the abundance of active sites provided by the PCN photoanode nanosheet, which promotes the transport rates of OER-relevant species. These PCN films provide a new benchmark for PCN photoanode materials.
ABSTRACT
The photocatalysts for hexavalent uranium (U(VI)) reduction suffered from the low uranium uptake capacity and weak long-wavelength light absorption. Herein, we synthesized the CdSxTe1-x nanobelts capped by ethylenediamine (EDA), which provided amino groups as the adsorption sites. With the increase of the Te content, the amino groups on the CdSxTe1-x nanobelts decreased because of the variation of the electron density of Cd2+, whereas the light adsorption was enhanced due to the narrowed bandgap. In photocatalytic reduction of U(VI), the CdS0.95Te0.05-EDA nanobelts exhibited a considerable U(VI) removal ratio of 97.4% with a remarkable equilibrium U(VI) extraction amount on per weight unit of the adsorbent (qe) of 836 mg/g. The bandgap structure and Fourier transform infrared spectroscopy (FT-IR) spectra analysis revealed that the optimum photocatalytic activity of CdSxTe1-x nanobelts was achieved at a 5% of Te2- doping, which balanced the factors of amino groups and bandgap. This adsorption-photoreduction process offers an ultrahigh uranium extraction capacity over wide uranium concentrations.
ABSTRACT
As a promising candidate for CO2 electroreduction, metal chalcogenides suffer from limited carrier density, which hampers the electron transport of electrocatalysts and activation of CO2. Herein, we have modified In2S3 nanosheets by in situ forming metallic In nanoparticles for enhanced CO2 electroreduction. The In-In2S3 hybrid nanosheets exhibited a remarkable geometrical current density of 70.3 mA cm-2 at -1.1 V vs. RHE, with 62.1 mA cm-2 for the carbonaceous product. The faradaic efficiency of the In-In2S3 hybrid nanosheets for the carbonaceous product reached 90% at -1.0 V vs. RHE, including 76% for formate production and 14% for CO production. The mechanistic study revealed that the improved performance by forming In nanoparticles on In2S3 nanosheets originated from the increased carrier density of the electrocatalysts and the decreased work function, which benefited the CO2 activation.
