| Recently,the use of hydrogen energy has solved the problem of global energy shortage and environmental pollution.It is the most ideal and potential hydrogen production technology to use visible light water splitting.Ta3N5 based compounds have ideal valence band position,band gap is about 2.1 eV,absorption band edge can be extended to 600 nm,theoretical solar hydrogen conversion efficiency is 15.9%,which is an ideal material for solar photocatalytic water solution.However,its intrinsic drawbacks including low charge carrier separation efficiency,poor carrier transportation,and easy self-oxidation by photogenerated holes have impeded its commercial application.The preparation process of Rh modified Ta3N5 based compounds was studied by controlling the nitriding time and temperature.The results show that the Rh modified Ta3N5 based samples?Rh-Ta-6?have high photocurrent intensity(3.84?A·cm-2),Compared with the unmodified Ta2O5@Ta3N5(0.19?A·cm-2),the photocurrent intensity of the Rh modified Ta3N5 based sample?Rh-Ta-1000?prepared by nitriding for 3 h at 1000?is higher(8.34?A·cm-2),which is about 43 times higher than that of the unmodified Ta2O5@Ta3N5,about 2 times higher than Rh-Ta-6.The photocatalytic activity test showed that although Rh-Ta-1000 showed high photocurrent intensity,its hydrogen production performance was lower than that of Rh-Ta-6.It is confirmed that the preparation process of Rh modified Ta3N5 based compound prepared by nitriding at 850?for 6 h is the best.A multiple core-shell heterostructure Rh-Rh3+modified Ta2O5@TaON@Ta3N5nanophotocatalyst was successfully constructed through nitriding Rh3+-Ta2O5nanoparticles,which exhibited a much higher carrier separation efficiency about one order of magnitude higher than Ta2O5@Ta3N5 precursor,and thus an excellent visible light photocatalytic H2-evolution activity(83.64?mol·g-1·h-1),much superior to Rh anchored Ta2O5@TaON(39.41?mol·g-1·h-1),and improved stability due to the residual Rh-O/N in Ta3N5 shell layer.Rh-modifying significantly extended light absorption to overall visible region.Localized built-in electric fields with hierarchical potential gradients at the multi-interfaces including a Rh/Ta3N5 Schottky junction and double n-n Ta3N5/Ta ON/Ta2O5 mutant heterojunctions,drove charge carriers to directionally transfer from inside to outside,and efficiently separate.Enhanced photoactivity was ascribed to a synergetic effect of improved light absorption ability,increased carrier separation efficiency,and accelerated surface reaction.A promising strategy of developing excellent Ta3N5-based photocatalysts for solar energy conversion is provided by constructing double n-n mutant heterojunctions. |
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