Nontrivial topological surface states (TSSs), which possess extraordinary carrier mobility and are protected by the bulk symmetry, have emerged as an innovative platform to search for efficient electrocatalysts toward hydrogen evolution reaction (HER). Here, a Sn-based nontrivial metal Ru 3 Sn 7 is prepared using electrical arc melting method. The results indicate that the (001) crystal family of Ru 3 Sn 7 possesses nontrivial TSSs with linear dispersion relation and large nontrivial energy window. Experimental and theoretical results demonstrate that nontrivial TSSs of Ru 3 Sn 7 can significantly boost charge transfer kinetics and optimize adsorption of hydrogen intermediates due to bulk symmetry-protected band structures. As expected, nontrivial Ru 3 Sn 7 exhibits superior HER activity to Ru, Pt/C, and trivial counterparts (e.g., Ru 2 Sn 3 , IrSn 2 , and Rh 3 Sn 2 ) with higher ratios of noble metals. Furthermore, the wide pH-range activity of topologically nontrivial Ru 3 Sn 7 implies the robustness of its TSSs against pH variation during the HER. These findings provide a promising approach to the rational design of topologically nontrivial metals as highly efficient electrocatalysts.
Four international standards, Ga1550, MMhb-1, Lp-6, Bern 4M, and one domestic standard BT-1 have been intercalibrated. The repeated measurements on MMhb-1 with different mass demonstrate that MMhb-1 is inhomogeneous in age and its average age is 519.8 Ma. The results of Bern 4M and Lp-6 reflect that they have an invariable value of 40 Ar*/ 39 Ar k (F) and the ages we obtained are consensus with their K-Ar age: Lp-6=127.7Ma; Bern 4M=18.2 Ma. Analyses of BT-1 age spectra, Ca/K and Cl/K spectra as well as inverse isochrons indicate that the sample is homogeneous and invariable and keeps close chemically, with its trapped argon isotope composition close to the atmosphere. The dating results show that age values are reproducible and steady, total fusion age, step-heating age, plateau age and isochron age are in accord with each other within the error range (2σ). Therefore, we recommend 28.7 Ma as the calibrated age of BT-1.We also discuss the variation in neutron flux gradients of Beijing 49-2 reactor. It was found that the neutron flux gradient varies considerably, and more monitors (standard samples) are needed to fix the trend of variation. The coefficient of the 49-2 reactor that transfers the ratio of production rate of 37 Ar Ca / 39 Ar K into Ca/K ratio is 1.78. This is different from that reported earlier, 2.0, which may be caused by the reconstruction of the reactor.
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