In order to understand the evolution of oxygen-rich layer (ORL) on titanium alloys, the near α titanium alloy TA15 and α+β type titanium alloy TC4 were thermally exposed in air at 850 °C to evaluate the effect...In order to understand the evolution of oxygen-rich layer (ORL) on titanium alloys, the near α titanium alloy TA15 and α+β type titanium alloy TC4 were thermally exposed in air at 850 °C to evaluate the effect of α phase content on formation and evolution of ORL, and the stability and diffusion of oxygen in α- and β-Ti were investigated by first principles calculations to reveal the oxygen diffusion rate. TA15 with more α phases has a higher diffusion coefficient of ORL evolution than TC4, resulting in forming thicker ORL on TA15 under the same thermal exposure condition. The first principles calculations indicate that octahedral interstice of α-Ti is the most stable site for oxygen atom. The nearest neighbor diffusion between octahedral interstices along the [0001] direction in α-Ti presenting the lowest activation energy is the most favorable oxygen diffusion mechanism in α- and β-Ti.展开更多
Noble metal palladium(Pd)is well‐known as excellent photocatalytic cocatalyst,but its strong adsorption to hydrogen causes its limited H2‐evolution activity.In this study,the transition metal Cu was successfully int...Noble metal palladium(Pd)is well‐known as excellent photocatalytic cocatalyst,but its strong adsorption to hydrogen causes its limited H2‐evolution activity.In this study,the transition metal Cu was successfully introduced into the metallic Pd to weaken its hydrogen‐adsorption strength to improve its interfacial H_(2)‐evolution rate via the Pd‐Cu alloying effect.Herein,the ultrasmall Pd_(100−x)Cu_(x) alloy nanodots(2−5 nm)as a novel H_(2)‐evolution cocatalyst were integrated with the TiO_(2) through a simple NaH_(2)PO_(2)‐mediated co‐deposition route.The resulting Pd_(100−x)Cu_(x)/TiO_(2) sample shows the significantly enhanced photocatalytic H_(2)‐generation performance(269.2μmol h^(−1)),which is much higher than the bare TiO2.Based on in situ irradiated X‐ray photoelectron spectroscopy(ISI‐XPS)and density functional theory(DFT)results,the as‐formed Pd_(100−x)Cu_(x) alloy nanodots can effectively promote the separation of photo‐generated charges and weak the adsorption strength for hydrogen to optimize the process of hydrogen‐desorption process on Pd_(75)Cu_(25) alloy,thus leading to high photocatalytic H_(2)‐evolution activity.Herein,the weakened H adsorption of Pd_(75)Cu_(25) cocatalyst can be ascribed to the formation of electron‐rich Pd after the introduction of weak electronegativity Cu.The present work about optimizing electronic structure for promoting interfacial reaction activity provides a new sight for the development of the highly efficient photocatalysts.展开更多
基金Project(51701128) supported by the National Natural Science Foundation of China
文摘In order to understand the evolution of oxygen-rich layer (ORL) on titanium alloys, the near α titanium alloy TA15 and α+β type titanium alloy TC4 were thermally exposed in air at 850 °C to evaluate the effect of α phase content on formation and evolution of ORL, and the stability and diffusion of oxygen in α- and β-Ti were investigated by first principles calculations to reveal the oxygen diffusion rate. TA15 with more α phases has a higher diffusion coefficient of ORL evolution than TC4, resulting in forming thicker ORL on TA15 under the same thermal exposure condition. The first principles calculations indicate that octahedral interstice of α-Ti is the most stable site for oxygen atom. The nearest neighbor diffusion between octahedral interstices along the [0001] direction in α-Ti presenting the lowest activation energy is the most favorable oxygen diffusion mechanism in α- and β-Ti.
文摘Noble metal palladium(Pd)is well‐known as excellent photocatalytic cocatalyst,but its strong adsorption to hydrogen causes its limited H2‐evolution activity.In this study,the transition metal Cu was successfully introduced into the metallic Pd to weaken its hydrogen‐adsorption strength to improve its interfacial H_(2)‐evolution rate via the Pd‐Cu alloying effect.Herein,the ultrasmall Pd_(100−x)Cu_(x) alloy nanodots(2−5 nm)as a novel H_(2)‐evolution cocatalyst were integrated with the TiO_(2) through a simple NaH_(2)PO_(2)‐mediated co‐deposition route.The resulting Pd_(100−x)Cu_(x)/TiO_(2) sample shows the significantly enhanced photocatalytic H_(2)‐generation performance(269.2μmol h^(−1)),which is much higher than the bare TiO2.Based on in situ irradiated X‐ray photoelectron spectroscopy(ISI‐XPS)and density functional theory(DFT)results,the as‐formed Pd_(100−x)Cu_(x) alloy nanodots can effectively promote the separation of photo‐generated charges and weak the adsorption strength for hydrogen to optimize the process of hydrogen‐desorption process on Pd_(75)Cu_(25) alloy,thus leading to high photocatalytic H_(2)‐evolution activity.Herein,the weakened H adsorption of Pd_(75)Cu_(25) cocatalyst can be ascribed to the formation of electron‐rich Pd after the introduction of weak electronegativity Cu.The present work about optimizing electronic structure for promoting interfacial reaction activity provides a new sight for the development of the highly efficient photocatalysts.
