Fully stoichiometric Cu2BaSn(S1-x Se x )4 solar cells via chemical solution deposition.

Cu2BaSn(S1-x Se x )4 has shown great prospects in the photoelectric field due to Earth-abundance, low toxicity, cost efficiency, direct bandgap, high absorption coefficient (>104 cm-1) and reduced anti-site disorder relative to Cu2ZnSn(S1-x Se x )4. A fully-tunable ratio of S/Se is the key to broaden the bandgap of Cu2BaSn(S1-x Se x )4. Here, we introduce a thionothiolic acid metathesis process to readily tune the stoichiometry of Cu2BaSn(S1-x Se x )4 films for the first time. Different stoichiometric Se/(S + Se) of Cu2BaSn(S1-x Se x )4 from zero to one can vary the bandgap range from 2 to 1.68 eV. The grain size of Cu2BaSn(S1-x Se x )4 films can be grown more than 10 µm. The optimized bandgap and high-quality growth of Cu2BaSn(S1-x Se x )4 films ensure the best power conversion efficiency of 2.01% for solution-processed Cu2BaSn(S1-x Se x )4 solar cells. This method provides an alternative solution-processed way for the synthesis of fully stoichiometric Cu2BaSn(S1-x Se x )4.

Fe-rich biomass derived char for microwave-assisted methane reforming with carbon dioxide.

Microwave-assisted methane reforming with carbon dioxide was dealt with in this work, using a Fe-rich biomass-derived char by one-step preparation. The main factors on the reforming reaction and stability of this catalyst were evaluated, together with a series of characterization on the produced gas and the used char. The char obtained from biomass pyrolysis with Fe2O3 addition of 10% exhibited the best performance on dry reforming reaction. A target CH4 conversion of 95% over this char was realized at 800 °C. Moreover, H2/CO ratio achieved with this char was prone to approach the stoichiometric value. Compared to CO2 conversion, CH4 conversion was more promoted with the increase of CO2/CH4 ratio. The variation of CO2/CH4 ratio also leaded to a noticeable changes on H2/CO ratio. More importantly, the selected char presented a satisfied stability, evidenced by the total decrease of 4.8% for CH4 conversion and 3.1% for CO2 conversion in the test of 160 min. This was contributed to a depressed in-situ carbon consumption and a moderate deterioration of porous structure. Gaseous products obtained with the appropriate char in a long run had a syngas content of 88.79% and H2/CO ratio of 0.92 on average.