Ambient electrochemical N2 reduction is emerging as a highly promising alternative to the Haber–Bosch process but is typically hampered by a high reaction barrier and competing hydrogen evolution, leading to an extremely low Faradaic efficiency. Here, we demonstrate that under ambient conditions, a single-atom catalyst, iron on nitrogen-doped carbon, could positively shift the ammonia synthesis process to an onset potential of 0.193 V, enabling a dramatically enhanced Faradaic efficiency of 56.55%. The only doublet coupling representing 15NH4+ in an isotopic labeling experiment confirms reliable NH3 production data. Molecular dynamics simulations suggest efficient N2 access to the single-atom iron with only a small energy barrier, which benefits preferential N2 adsorption instead of H adsorption via a strong exothermic process, as further confirmed by first-principle calculations. The released energy helps promote the following process and the reaction bottleneck, which is widely considered to be the first hydrogenation step, is successfully overcome.

By substituting Fe with the 5d-transition metal Pt in BaFe2As2, we have successfully synthesized the superconductors BaFe2−xPtxAs2. The systematic evolution of the lattice constants indicates that the Fe ions were successfully replaced by Pt ions. By increasing the doping content of Pt, the antiferromagnetic order and structural transition of the parent phase is suppressed and superconduc-tivity emerges at a doping level of about x = 0.02. At a doping level of x = 0.1, we get a maximum transition temperature Tc of about 25 K. While even for this optimally doped sample, the residual resistivity ratio (RRR) is only about 1.35, indicating a strong impurity scattering effect. We thus argue that the doping to the Fe-sites naturally leads to a high level impurity scattering, although the superconductivity can still survive at about 25 K. The synchrotron powder x-ray diffraction shows that the resistivity anomaly is in good agreement with the structural transition. The super-conducting transitions at different magnetic fields were also measured at the doping level of about x = 0.1, yielding a slope of-dHc2/dT = 5.4 T/K near Tc. Finally a phase diagram was established for the Pt doped 122 system. Our results suggest that superconductivity can also be easily induced in the FeAs family by substituting the Fe with Pt, with almost the similar maximum transition temperatures as doping Ni, Co, Rh and Ir.

We present a study of angle-resolved quantum oscillations of electric and thermoelectric transport coefficients in semi-metallic WTe2, which has the particularity of displaying a large B 2 magnetoresistance. The Fermi surface consists of two pairs of electron-like and hole-like pockets of equal volumes in a "Russian doll" structure. Carrier density, Fermi energy, mobility and the mean-freepath of the system are quantified. An additional frequency is observed above a threshold field and attributed to magnetic breakdown across two orbits. In contrast to all other dilute metals, the Nernst signal remains linear in magnetic field even in the high-field (ωcτ ≫ 1) regime. Surprisingly, none of the pockets extend across the c-axis of the first Brillouin zone, making the system a three-dimensional metal with moderate anisotropy in Fermi velocity yet a large anisotropy in mean-free-path. 2 ) was reported with no sign of saturation up to 60 T[6]. This is the expected behavior of a perfectly-compensated semi-metal [7], but has not been seen in bismuth [8] or graphite [9], two compensated semi-metals whose Fermi surface is accurately known. A first step towards uncovering the ultimate reason behind the quadratic magnetoresistance of WTe 2 is a quantitative determination of the structure of the Fermi surface and the components of the mobility tensor.In this letter, we report on a study of quantum oscillations of resistivity, Seebeck and Nernst coefficients in high-quality single crystals of WTe 2 and find that the Fermi surface consists of two pairs of electron-like and hole-like pockets. Each pair is concentric with identical structure like a set of Russian dolls. The anisotropy is much smaller than one would naively expect in a layered system. The longer axis of the pockets is much shorter than the height of the Brillouin zone, in contrast to the theoretical expectations. Moreover, we find another distinctive feature of this semi-metal in addition to quadratic magnetoresistance, which is a Nernst response linear in magnetic field deep inside the high-field limit. Our results quantify carrier concentration of the system and set plausible quantitative windows for mobilities and Fermi energies leading to the huge quadratic magnetoresistance and large field-linear Nernst signal.