A series of MoP/γ-Al2O3 catalysts with MoP loadings of 5%20% were prepared by direct reduction of the corresponding molybdenum phosphate precursors.Different preparation methods were considered to 20% MoP/γ-Al2O3.Th...A series of MoP/γ-Al2O3 catalysts with MoP loadings of 5%20% were prepared by direct reduction of the corresponding molybdenum phosphate precursors.Different preparation methods were considered to 20% MoP/γ-Al2O3.The catalysts prepared were characterized by XRD and TG-DTG.The catalytic activity was tested in a continuous flow type microreactor at 340℃,370℃and 3.0MPa.A liquid containing thiophene,pyridine,cyclohexene was used as the model compounds.The results indicate that the active species of supported catalysts are dispersed well on the surface of the supporters,the weight loss of supported catalysts in TG-DTG analysis occurs earlier than unsupported ones.It is found that supported MoP is much more active than unsupported ones and it could maintain higher HYD conversions without loss of HDN activity.The 13% of MoP loading catalyst was most active,the conversion of pyridine,thiophene and cyclehexene could reach 99.15%,98.23% and 100% respectively.The preparation method that γ-Al2O3 was added in at the same time is better than other methods.展开更多
Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide （MOP） is theoretically capable o...Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide （MOP） is theoretically capable of efficient hydrogen evolution reaction （HER） catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon （MoP@NPCNFs） to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.展开更多
γ-Al2O3-supported molybdenum nitride,molybdenum phosphide and molybdenum carbide catalysts for hydrodesulphurization were prepared,respectively,by temperature-programmed reaction.The precursors were obtained by impre...γ-Al2O3-supported molybdenum nitride,molybdenum phosphide and molybdenum carbide catalysts for hydrodesulphurization were prepared,respectively,by temperature-programmed reaction.The precursors were obtained by impregnation of γ-Al2O3 in an aqueous solution of ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24·4H2O] and diammonium hydrogen phosphate [(NH4)2HPO4],followed by drying at 120 ℃ and calcining at 500 ℃ in air.The three kinds of catalysts were characterized by XRD and BET.The results indicated that the molybdenum carbide prepared at a space velocity(CH4-H2) of 10 800 h-1 has the biggest surface area of 175.7 m2/g.The pore size distribution of molybdenum nitride catalyst was complex.The small pores of about 0.622 5 nm and the big pores of about 3.736 nm were mainly observed in the supported molybdenum nitride catalyst.The active components in all of the three catalysts were dispersed on γ-Al2O3 uniformly.The conversion of dibenzothiophene on the three catalysts could respectively reach 85.5%、81% and 78.6%.展开更多
Molybdenum phosphide (MoP) flakes were synthesized by the reduction of hexaammonium heptamolybdate tetrahydrate and ammonium dihydrogen phosphate. The flakes are porous and constructed by MoP nanoparticles with ca. 10...Molybdenum phosphide (MoP) flakes were synthesized by the reduction of hexaammonium heptamolybdate tetrahydrate and ammonium dihydrogen phosphate. The flakes are porous and constructed by MoP nanoparticles with ca. 100 nm diameters. The lateral size of flakes ranges from less than 1 μm to larger than 5 μm, and the thickness of MoP fakes is ca. 200 nm. The mixture of MoP flakes and carbon black exhibits effective catalytic activity in the hydrogen evolution reaction. The optimal overpotential required for 20 mA·cm﹣2 current density is 155 mV in acidic solution and 184 mV in basic solution. The mixture can work stably in long-term hydrogen generation in both acidic and basic solution. The faradaic yield of mixture in hydrogen evolution reaction is nearly 100% in both acidic and basic solution. The Mo and P species in MoP flakes are found to have small positive and negative charge, respectively. The catalytic activity of MoP flakes is likely to be correlated with this charged nature.展开更多
文摘A series of MoP/γ-Al2O3 catalysts with MoP loadings of 5%20% were prepared by direct reduction of the corresponding molybdenum phosphate precursors.Different preparation methods were considered to 20% MoP/γ-Al2O3.The catalysts prepared were characterized by XRD and TG-DTG.The catalytic activity was tested in a continuous flow type microreactor at 340℃,370℃and 3.0MPa.A liquid containing thiophene,pyridine,cyclohexene was used as the model compounds.The results indicate that the active species of supported catalysts are dispersed well on the surface of the supporters,the weight loss of supported catalysts in TG-DTG analysis occurs earlier than unsupported ones.It is found that supported MoP is much more active than unsupported ones and it could maintain higher HYD conversions without loss of HDN activity.The 13% of MoP loading catalyst was most active,the conversion of pyridine,thiophene and cyclehexene could reach 99.15%,98.23% and 100% respectively.The preparation method that γ-Al2O3 was added in at the same time is better than other methods.
文摘Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide （MOP） is theoretically capable of efficient hydrogen evolution reaction （HER） catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon （MoP@NPCNFs） to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.
文摘γ-Al2O3-supported molybdenum nitride,molybdenum phosphide and molybdenum carbide catalysts for hydrodesulphurization were prepared,respectively,by temperature-programmed reaction.The precursors were obtained by impregnation of γ-Al2O3 in an aqueous solution of ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24·4H2O] and diammonium hydrogen phosphate [(NH4)2HPO4],followed by drying at 120 ℃ and calcining at 500 ℃ in air.The three kinds of catalysts were characterized by XRD and BET.The results indicated that the molybdenum carbide prepared at a space velocity(CH4-H2) of 10 800 h-1 has the biggest surface area of 175.7 m2/g.The pore size distribution of molybdenum nitride catalyst was complex.The small pores of about 0.622 5 nm and the big pores of about 3.736 nm were mainly observed in the supported molybdenum nitride catalyst.The active components in all of the three catalysts were dispersed on γ-Al2O3 uniformly.The conversion of dibenzothiophene on the three catalysts could respectively reach 85.5%、81% and 78.6%.
文摘Molybdenum phosphide (MoP) flakes were synthesized by the reduction of hexaammonium heptamolybdate tetrahydrate and ammonium dihydrogen phosphate. The flakes are porous and constructed by MoP nanoparticles with ca. 100 nm diameters. The lateral size of flakes ranges from less than 1 μm to larger than 5 μm, and the thickness of MoP fakes is ca. 200 nm. The mixture of MoP flakes and carbon black exhibits effective catalytic activity in the hydrogen evolution reaction. The optimal overpotential required for 20 mA·cm﹣2 current density is 155 mV in acidic solution and 184 mV in basic solution. The mixture can work stably in long-term hydrogen generation in both acidic and basic solution. The faradaic yield of mixture in hydrogen evolution reaction is nearly 100% in both acidic and basic solution. The Mo and P species in MoP flakes are found to have small positive and negative charge, respectively. The catalytic activity of MoP flakes is likely to be correlated with this charged nature.
