Yubo Luo

Hexagonal-Phase Cobalt Monophosphosulfide for Highly Efficient Overall Water Splitting

The rational design and synthesis of nonprecious, efficient, and stable electrocatalysts to replace precious noble metals are crucial to the future of hydrogen economy. Herein, a partial sulfurization/phosphorization strategy is proposed to synthesize a nonstoichiometric pyrrhotite-type cobalt monophosphosulfide material (Co0.9S0.58P0.42) with a hexagonal close-packed phase for electrocatalytic water splitting. By regulating the degree of sulfurization, the P/S atomic ratio in the cobalt monophosphosulfide can be tuned to activate the Co3+/Co2+ couples. The synergy between the nonstoichiometric nature and the tunable P/S ratio results in the strengthened Co3+/Co2+ couples and tunable electronic structure and thus efficiently promotes the oxygen/hydrogen evolution reaction (OER/HER) processes toward overall water splitting. Especially for OER, the Co0.9S0.58P0.42 material, featured with a uniform yolk-shell spherical morphology, shows a low overpotential of 266 mV at 10 mA cm-2 (η10) with a low Tafel slope of 48 mV dec-1 as well as high stability, which is comparable to that of the reported promising OER electrocatalysts. Coupled with the high HER activity of Co0.9S0.58P0.42, the overall water splitting is demonstrated with a low η10 at 1.59 V and good stability. This study shows that phase engineering and composition control can be the elegant strategy to realize the Co3+/Co2+ couple activation and electronic structure tuning to promote the electrocatalytic process. The proposed strategy and approaches allow the rational design and synthesis of transition metal monophosphosulfides toward advanced electrochemical applications.

Recent advances in printable secondary batteries

In past decades, with interest in wearable smart devices rapidly growing, the design and fabrication of novel energy storage devices have received increasing attention. Although secondary batteries are among the best options in this area, their bulky construction remains unable to fulfil the specific demands of miniaturization, portability, and flexibility. This review comprises a brief update on recent progress in printable secondary batteries, in combination with their principles and frequently used printing techniques. Moreover, we also discuss the challenges and advantages of printed secondary batteries and describe their future prospects in wearable smart devices.

Designing hybrid architectures for advanced thermoelectric materials

In recent decades, thermoelectric materials have garnered extensive interest and shown promising applications in energy conversion. The present review demonstrates the recent progress in the design of advanced hybrid thermoelectric nanocomposites mainly prepared by solution synthesis. Then the state-of-the-art strategies have been discussed for either enhancing the power factor or reducing the thermal conductivity. In some cases, the obtained peak ZT values are comparable to or superior to those of the traditional solid-state synthesized materials. Finally, we highlight the current challenges and future opportunities in the solution-synthesized thermoelectric nanocomposites.

Enhancement of the thermoelectric performance of CuInTe 2 via SnO 2 in situ replacement

Inxa0situ induced nanostructure is employed as an alternative way to enhance the thermoelectric performance of p-type CuInTe2 based thermoelectric materials in this work. Dispersive In2O3 nanoparticles are formed in the samples with SnO2 by virtue of the in situ replacement of SnO2 and CuInTe2. As a result, an obvious reduction in the thermal conductivity has been achieved due to the intensive scattering of phonon by the in situ formed In2O3 nanoparticles. In addition, the power factor of CuInTe2 is less effected by SnO2 additive. Eventually, an enhanced ZT of 1.1 at 823xa0K has been achieved for the CuInTe2–0.5% SnO2 sample.

Improved densification and thermoelectric performance of In 5 SnSbO 12 via Ga doping

In5SnSbO12 is being considered for use in thermoelectric applications. It has a satisfactory electrical conductivity and is expected to possess low thermal conductivity. However, it is difficult to densify In5SnSbO12 by conventional solid-state reaction method. In this work, we demonstrated that Ga doping could increase the relative density of In5SnSbO12, from ~xa060% (xxa0=xa00) to ~xa090% (xxa0=xa00.1). The improved densification may be attributable to the increased cationic occupancy after the addition of Ga and the reduced grain size induced by the presence of the secondary phase Ga2In6Sn2O16. The improved relative density led to a significant reduction in electrical resistivity; for example, for xxa0=xa00.1, the lowest electrical resistivity was ~xa00.002xa0Ωxa0cm at 973xa0K, which was five times lower than that of the undoped sample (xxa0=xa00). The resultant power factor of this sample had a value of 3.4xa0×xa010−4xa0Wm−1xa0K−2 at 973xa0K, which was nearly four times higher than that of the undoped sample. Although thermal conductivities were increased with Ga doping due to the enhanced densification, they were lower than that of In2O3. The highest thermoelectric performance was achieved in the sample with xxa0=xa00.05, specifically zTxa0~xa00.17 at 973xa0K. These results indicate that the addition of Ga to In5SnSbO12 results in a material which is more promising for thermoelectric applications.

Porous MXene Frameworks Support Pyrite Nanodots toward High-Rate Pseudocapacitive Li/Na-Ion Storage

Presented are the novel Ti3C2 T x MXene-based nanohybrid that decorated by pyrite nanodots on its surface (denoted as FeS2@MXene). The nanohybrid was obtained by the one-step sulfurization of self-assembled iron hydroxide@MXene precursor. When used for Li/Na-ion storage, the FeS2@MXene nanohybrid present excellent rate capabilities. Particularly, for Li-ion storage, an elevated reversible specific capacity of 762 mAh g-1 at 10 A g-1 after 1000 cycles was achieved. And for Na-ion storage, the FeS2@MXene nanohybrid also delivering a reversible specific capacity of 563 mAh g-1 after 100 cycles at a current density of 0.1 A g-1.