Wenqing Zhang

The development of low‐cost and highly efficient electrocatalysts for the widespread application in rechargeable Li‐O₂ batteries is still a major research challenge. Herein, porous N‐doped graphene, decorated with Fe/Fe₃N/Fe₄N nanoparticles is designed and synthesized via a one‐step pyrolysis of easily available precursors. It is found that the Fe/Fe₃N/Fe₄N nanoparticles are uniformly dispersed on the N‐doped graphene substrate, and that both the nanoparticles and the substrate can facilitate the electrochemical reaction. When the rationally designed material is used as cathode in Li‐O₂ batteries, it exhibits excellent electrochemical performance, delivering a high capacity of 7397.8 mAh g⁻¹ and showing impressive cycle stability of over 100 steady cycles. The excellent performance of this material is attributed to the good synergistic effect of uniformly distributed nanoparticles and the porosity of the substrate. These results indicate that the N‐doped graphene decorated with Fe/Fe₃N/Fe₄N is an excellent cathode catalyst for Li‐O₂ batteries and would also be a promising new material for other energy storage devices.

In Te-free (Bi,Sb)₂Se₃, structural transition induced electronic band convergence and intensified phonon scattering triple the thermoelectricZTto 1.0.

Contrary to the conventional belief that the consideration for topological insulators (TIs) as potential thermoelectrics is due to their excellent electrical properties benefiting from the topological surface states, this work shows that the 3D weak TIs, formed by alternating stacks of quantum spin Hall layers and normal insulator (NI) layers, can also be decent thermoelectrics because of their focus on minimum thermal conductivity. The minimum lattice thermal conductivity is experimentally confirmed in Bi₁₄Rh₃I₉ and theoretically predicted for Bi₂TeI at room temperature. It is revealed that the topologically “trivial” NI layers play a surprisingly critical role in hindering phonon propagation. The weak bonding in the NI layers gives rise to significantly low sound velocity, and the localized low‐frequency vibrations of the NI layers cause strong acoustic–optical interactions and lattice anharmonicity. All these features are favorable for the realization of exceptionally low lattice thermal conductivity, and therefore present remarkable opportunities for developing high‐performance thermoelectrics in weak TIs.

Electronegative guests filled into CoSb₃yield a unique “cluster vibration” that provides a new perspective on designing novel inclusion compounds.

We proposed a geometry strategy to engineer the radiative recombination possibility and thus the lifetime of excitons in nanowires of some photovoltaic semiconductors by using theoretical analysis and first-principles calculations. We demonstrated that the shape can engineer the symmetry of the wave-functions of band-edge states and influence the radiative recombination possibility. The nanowires need to satisfy the following requirements to forbid the radiative recombination possibility of band-edge excitons: (i) wurtzite structure; (ii) p_xy-characterized wave-function of VBM state and (iii) C_3v-symmetry shape. The geometrical symmetry results in the p_xy-characterized C_3v-symmetry wave-function of VBM state and leads to forbidden radiative recombination of band-edge excitons. The geometry strategy offers a flexible proposal to prolong the exciton lifetime, leaving optical absorption impregnable.

During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon–phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions.

Rashba semiconductors are of great interest in spintronics, superconducting electronics and thermoelectrics. Bulk BiTeI is a new Rashba system with a giant spin–split band structure. 2D-like thermoelectric response has been found in BiTeI. However, as optimizing the carrier concentration, the bipolar effect occurs at elevated temperature and deteriorates the thermoelectric performance of BiTeI. In this paper, band gap engineering in Rashba semiconductor BiTeI through Br-substitution successfully reduces the bipolar effect and improves the thermoelectric properties. By utilizing the optical absorption and Burstein–Moss-effect analysis, we find that the band gap in Rashba semiconductor BiTeI increases upon bromine substitution, which is consistent with theoretical predictions. Bipolar transport is mitigated due to the larger band gap, as the thermally-activated minority carriers diminish. Consequently, the Seebeck coefficient keeps increasing with a corresponding rise in temperature, and thermoelectric performance can thus be enhanced with a ZT = 0.5 at 570 K for BiTeI _0.88 Br _0.12 .

A definitive determination of crystal structures is an important prerequisite for designing and exploiting new functional materials. We find that the long-assumed TMB₂phases of multifunctional tungsten and molybdenum borides are in fact a family of complex TMB₃polytypes.

Unraveling the descriptor of catalytic activity, which is related to physical properties of catalysts, is a major objective of catalysis research. In the present study, the first-principles calculations based on interfacial model were performed to study the oxygen evolution reaction mechanism of Li2O2 supported on active surfaces of transition-metal compounds (TMC: oxides, carbides, and nitrides). Our studies indicate that the O2 evolution and Li+ desorption energies show linear and volcano relationships with surface acidity of catalysts, respectively. Therefore, the charging voltage and desorption energies of Li+ and O2 over TMC could correlate with their corresponding surface acidity. It is found that certain materials with an appropriate surface acidity can achieve the high catalytic activity in reducing charging voltage and activation barrier of rate-determinant step. According to this correlation, CoO should have as active catalysis as Co3O4 in reducing charging overpotential, which is further confir...