This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(formi...This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(forming ZKL alloy).The results indicate that the introduction of CeO_(2)and La_(2)O_(3)promotes the precipita-tion of T-(Mg_(1−x),Zn_(x))_(11)RE phases(Mg-Zn-RE phases,where RE represents Ce or La)at grain boundaries.The presence and distribution pattern of the T-phase have a profound impact on the corrosion resis-tance of the Mg alloy.Specifically,the ZKC alloy exhibits the most outstanding corrosion resistance.This superior performance is attributed to the uniform distribution of(Mg_(1−x),Zn_(x))_(11)Ce phase at grain bound-aries in ZK60-0.5 wt%CeO_(2),effectively hindering the penetration of corrosive media into the matrix.Additionally,scanning kelvin probe force microscopy(SKPFM)analysis reveals that the(Mg_(1−x),Zn_(x))_(11)Ce phase exhibits the smallest potential difference with the matrix,significantly mitigating the tendency for galvanic corrosion.In contrast,the ZKL alloy displays less precipitation and uneven distribution of the(Mg_(1−x),Zn_(x))_(11)La phase,resulting in inferior corrosion resistance compared to the ZKC alloy.The dispar-ities in the precipitation of the two phases,as derived from first-principles calculations,stem from the spontaneous reduction of CeO_(2)under Mg conditions,whereas the reduction reaction between La_(2)O_(3)and Mg cannot proceed spontaneously.Furthermore,SKPFM analysis and CALPHAD method found that as the addition of CeO_(2)/La_(2)O_(3)increases,the atomic ratio of Zn in the Mg-Zn-RE ternary phase rises,accompa-nied by an increase in the potential difference between the Mg-Zn-RE phase and the Mg matrix.This suggests that fine-tuning the addition of rare earth oxides can modify the atomic ratio of the Mg-Zn-RE ternary phase,thereby enhancing the corrosion resistance of the Mg alloy.In summary,this study not only unravels the specific mechanisms of how CeO_(2)and La_(2)O_(3)affect the corrosion behavior of ZK60 Mg alloy but also provides new strategies and insights for the development of low-cost,high-performance corrosion-resistant Mg alloy materials.展开更多
Optimizing the energy barrier of 2H-to-1T phase transformation plays a crucial role in modulating the intrinsic electronic structure of MoS_(2)to achieve satisfactory water-splitting performance,but remains a signific...Optimizing the energy barrier of 2H-to-1T phase transformation plays a crucial role in modulating the intrinsic electronic structure of MoS_(2)to achieve satisfactory water-splitting performance,but remains a significant challenge.Herein,we report a vacancy occupation-triggered phase transition strategy to fabricate a core-shell 1T phase nanorod structure,which is composed of S-vacancies decorated MoS_(2)as the core,and N,P co-doped carbons as the shell(1T-MoS_(2)@NPC).The co-insertion of N and P dopants into MoS_(2)can occupy partial S-vacancies,triggering a phase transformation from the semiconducting 2H phase to the conducting 1T phase with a reduced energy barrier.Profiting from the strong coupling effect between N,P dopants and S-vacancies,the as-made 1T-MoS_(2)@NPC exhibits excellent electrocatalytic activity for both HER(η_(10)=148 m V)and OER(η_(10)=232 mV)in alkaline solution.Meanwhile,a low cell voltage of 1.62 V is needed to drive a current density of 10mA cm^(-2)in 1.0 M KOH electrolyte.The theoretical calculation results reveal that the S-vacancies decorated C atoms in the meta-position relative to N,P atoms represent the most active HER and OER sites,which synergistically upshift the d band center and balance the rate-determining step,thus ensuring the simultaneous optimization of adsorption free energy and electronic structure.This vacancy-occupation-derived phase transformation strategy caused by non-metallic doping may provide valuable guidance for enhancing the performance of alkaline water electrolysis.展开更多
基金financial support from the National Natural Science Foundation of China(No.52201104)the Natural Science Foundation of Hunan Province(No.2023JJ40032)the Education Department of Hunan Province of China(No.24B0321).
文摘This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(forming ZKL alloy).The results indicate that the introduction of CeO_(2)and La_(2)O_(3)promotes the precipita-tion of T-(Mg_(1−x),Zn_(x))_(11)RE phases(Mg-Zn-RE phases,where RE represents Ce or La)at grain boundaries.The presence and distribution pattern of the T-phase have a profound impact on the corrosion resis-tance of the Mg alloy.Specifically,the ZKC alloy exhibits the most outstanding corrosion resistance.This superior performance is attributed to the uniform distribution of(Mg_(1−x),Zn_(x))_(11)Ce phase at grain bound-aries in ZK60-0.5 wt%CeO_(2),effectively hindering the penetration of corrosive media into the matrix.Additionally,scanning kelvin probe force microscopy(SKPFM)analysis reveals that the(Mg_(1−x),Zn_(x))_(11)Ce phase exhibits the smallest potential difference with the matrix,significantly mitigating the tendency for galvanic corrosion.In contrast,the ZKL alloy displays less precipitation and uneven distribution of the(Mg_(1−x),Zn_(x))_(11)La phase,resulting in inferior corrosion resistance compared to the ZKC alloy.The dispar-ities in the precipitation of the two phases,as derived from first-principles calculations,stem from the spontaneous reduction of CeO_(2)under Mg conditions,whereas the reduction reaction between La_(2)O_(3)and Mg cannot proceed spontaneously.Furthermore,SKPFM analysis and CALPHAD method found that as the addition of CeO_(2)/La_(2)O_(3)increases,the atomic ratio of Zn in the Mg-Zn-RE ternary phase rises,accompa-nied by an increase in the potential difference between the Mg-Zn-RE phase and the Mg matrix.This suggests that fine-tuning the addition of rare earth oxides can modify the atomic ratio of the Mg-Zn-RE ternary phase,thereby enhancing the corrosion resistance of the Mg alloy.In summary,this study not only unravels the specific mechanisms of how CeO_(2)and La_(2)O_(3)affect the corrosion behavior of ZK60 Mg alloy but also provides new strategies and insights for the development of low-cost,high-performance corrosion-resistant Mg alloy materials.
基金supported by the National Natural Science Foundation of China(Grant No.22275210)the Natural Science Foundation of Shandong Province(Grant No.ZR2024QB025,ZR2023ME155)the Taishan Scholar Project of Shandong Province(tsqn202306226)。
文摘Optimizing the energy barrier of 2H-to-1T phase transformation plays a crucial role in modulating the intrinsic electronic structure of MoS_(2)to achieve satisfactory water-splitting performance,but remains a significant challenge.Herein,we report a vacancy occupation-triggered phase transition strategy to fabricate a core-shell 1T phase nanorod structure,which is composed of S-vacancies decorated MoS_(2)as the core,and N,P co-doped carbons as the shell(1T-MoS_(2)@NPC).The co-insertion of N and P dopants into MoS_(2)can occupy partial S-vacancies,triggering a phase transformation from the semiconducting 2H phase to the conducting 1T phase with a reduced energy barrier.Profiting from the strong coupling effect between N,P dopants and S-vacancies,the as-made 1T-MoS_(2)@NPC exhibits excellent electrocatalytic activity for both HER(η_(10)=148 m V)and OER(η_(10)=232 mV)in alkaline solution.Meanwhile,a low cell voltage of 1.62 V is needed to drive a current density of 10mA cm^(-2)in 1.0 M KOH electrolyte.The theoretical calculation results reveal that the S-vacancies decorated C atoms in the meta-position relative to N,P atoms represent the most active HER and OER sites,which synergistically upshift the d band center and balance the rate-determining step,thus ensuring the simultaneous optimization of adsorption free energy and electronic structure.This vacancy-occupation-derived phase transformation strategy caused by non-metallic doping may provide valuable guidance for enhancing the performance of alkaline water electrolysis.
