Enhance ZnO Photocatalytic Performance via Radiation Modified g-C3N4.

Environmental pollution, especially water pollution, is becoming increasingly serious. Organic dyes are one type of the harmful pollutants that pollute groundwater and destroy ecosystems. In this work, a series of graphitic carbon nitride (g-C3N4)/ZnO photocatalysts were facilely synthesized through a grinding method using ZnO nanoparticles and g-C3N4 as the starting materials. According to the results, the photocatalytic performance of 10 wt.% CN-200/Z-500 (CN-200, which g-C3N4 was 200 kGy, referred to the irradiation metering. Z-500, which ZnO was 500 °C, referred to the calcination temperature) with the CN-200 exposed to electron beam radiation was better than those of either Z-500 or CN-200 alone. This material displayed a 98.9% degradation rate of MB (20 mg/L) in 120 min. The improvement of the photocatalytic performance of the 10 wt.% CN-200/Z-500 composite material was caused by the improvement of the separation efficiency of photoinduced electron-hole pairs, which was, in turn, due to the formation of heterojunctions between CN-200 and Z-500 interfaces. Thus, this study proposes the application of electron-beam irradiation technology for the modification of photocatalytic materials and the improvement of photocatalytic performance.

Hydrogen production and solar energy storage with thermo-electrochemically enhanced steam methane reforming.

Hydrogen is widely regarded as a sustainable energy carrier with tremendous potential for low-carbon energy transition. Solar photovoltaic-driven water electrolysis (PV-E) is a clean and sustainable approach of hydrogen production, but with major barriers of high hydrogen production costs and limited capacity. Steam methane reforming (SMR), the state-of-the-art means of hydrogen production, has yet to overcome key obstacles of high reaction temperature and CO2 emission for sustainability. This work proposes a solar thermo-electrochemical SMR approach, in which solar-driven mid/low-temperature SMR is combined with electrochemical H2 separation and in-situ CO2 capture. The feasibility of this method is verified experimentally, achieving an average methane conversion of 96.8% at a dramatically reduced reforming temperature of 400-500 °C. The underlying mechanisms of this method are revealed by an experimentally calibrated model, which is further employed to predict its performance for thermo-electrochemical hydrogen production. Simulation results show that a net solar-to-H2 efficiency of 26.25% could be obtained at 500 °C, which is over 11 percentage points higher than that of PV-E; the first-law thermodynamic efficiency reaches up to 63.27% correspondingly. The enhanced efficiency also leads to decreased fuel consumption and lower CO2 emission of the proposed solar-driven SMR system. Such complementary conversion of solar PV electricity, solar thermal energy, and low-carbon fuel provides a synergistic and efficient means of sustainable H2 production with potentially long-term solar energy storage on a vast scale.