Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing exp...Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing experimental phenomena of alloy phase transitions during extremely slow variation in temperature by equilibrium thinking mode and then taking erroneous knowledge of experimental phenomena as selected information for establishing Gibbs energy function and so-called equilibrium phase diagram. Second, the equilibrium holographic network phase diagrams of AuCu3-type sublattice system may be used to describe systematic correlativity of the composition?temperature-dependent alloy gene arranging structures and complete thermodynamic properties, and to be a standard for studying experimental subequilibrium order-disorder transition. Third, the equilibrium transition of each alloy is a homogeneous single-phase rather than a heterogeneous two-phase, and there exists a single-phase boundary curve without two-phase region of the ordered and disordered phases; the composition and temperature of the top point on the phase-boundary curve are far away from the ones of the critical point of the AuCu3 compound.展开更多
The direct electrochemical conversion of CO_(2) to syngas with controllable composition remains challenging. In this work, driven by concentration gradient, a simple air-heating aided strategy has been developed to ad...The direct electrochemical conversion of CO_(2) to syngas with controllable composition remains challenging. In this work, driven by concentration gradient, a simple air-heating aided strategy has been developed to adjust surface composition of the self-supporting nanoporous AuCu_(3) alloy. According to Fick First Law, the interior Cu atoms of the AuCu_(3) alloy with Au-rich surface gradually segregated outwards during heating, realizing Cu-rich surface eventually. Correspondingly, the competing electrocatalytic CO_(2) reduction (ECR) to CO and hydrogen evolution reactions (HER) were tactfully balanced on these alloy surfaces, thus achieving proportion-tunable syngas (CO/H2). Density functional theory (DFT) calculations on the Gibbs free energy change of the COOH* and H* (ΔGCOOH*, ΔGH*) on the alloy surfaces were conducted, which are generally considered as the selectivity descriptors for CO and H2 products, respectively. It shows ΔGCOOH* gradually increases in contrast to the decreased ΔGH* with more Cu on the surface, suggesting H2 is more favored over Cu sites, which is consistent with the declining CO/H2 ratio observed in the experiments. This study reveals that the surface composition controls ECR activity of nanoporous AuCu_(3) alloy, providing an alternative way to the syngas production with desirable proportion.展开更多
基金Project(51071181)supported by the National Natural Science Foundation of ChinaProject(2013FJ4043)supported by the Natural Science Foundation of Hunan Province,China
文摘Taking AuCu3-type sublattice system as an example, three discoveries have been presented: First, the third barrier hindering the progress in metal materials science is that researchers have got used to recognizing experimental phenomena of alloy phase transitions during extremely slow variation in temperature by equilibrium thinking mode and then taking erroneous knowledge of experimental phenomena as selected information for establishing Gibbs energy function and so-called equilibrium phase diagram. Second, the equilibrium holographic network phase diagrams of AuCu3-type sublattice system may be used to describe systematic correlativity of the composition?temperature-dependent alloy gene arranging structures and complete thermodynamic properties, and to be a standard for studying experimental subequilibrium order-disorder transition. Third, the equilibrium transition of each alloy is a homogeneous single-phase rather than a heterogeneous two-phase, and there exists a single-phase boundary curve without two-phase region of the ordered and disordered phases; the composition and temperature of the top point on the phase-boundary curve are far away from the ones of the critical point of the AuCu3 compound.
基金This work was financially supported by the National Natural Science Foundation of China(No.21771137)the Training Project of Innovation Team of Colleges and Universities in Tianjin(No.TD13-5020)the Natural Science Foundation of Tianjin City of China(No.18JCJQJC47700).
文摘The direct electrochemical conversion of CO_(2) to syngas with controllable composition remains challenging. In this work, driven by concentration gradient, a simple air-heating aided strategy has been developed to adjust surface composition of the self-supporting nanoporous AuCu_(3) alloy. According to Fick First Law, the interior Cu atoms of the AuCu_(3) alloy with Au-rich surface gradually segregated outwards during heating, realizing Cu-rich surface eventually. Correspondingly, the competing electrocatalytic CO_(2) reduction (ECR) to CO and hydrogen evolution reactions (HER) were tactfully balanced on these alloy surfaces, thus achieving proportion-tunable syngas (CO/H2). Density functional theory (DFT) calculations on the Gibbs free energy change of the COOH* and H* (ΔGCOOH*, ΔGH*) on the alloy surfaces were conducted, which are generally considered as the selectivity descriptors for CO and H2 products, respectively. It shows ΔGCOOH* gradually increases in contrast to the decreased ΔGH* with more Cu on the surface, suggesting H2 is more favored over Cu sites, which is consistent with the declining CO/H2 ratio observed in the experiments. This study reveals that the surface composition controls ECR activity of nanoporous AuCu_(3) alloy, providing an alternative way to the syngas production with desirable proportion.
