MOF-Derived CoSe2 Nanoparticles/Carbonized Melamine Foam as Catalytic Cathode Enabling Flexible Li-CO2 Batteries with High Energy Efficiency and Stable Cycling.

Rechargeable aprotic Li-CO2 batteries have aroused worldwide interest owing to their environmentally friendly CO2 fixation ability and ultra-high specific energy density. However, its practical applications are impeded by the sluggish reaction kinetics and discharge product accumulation during cycling. Herein, a flexible composite electrode comprising CoSe2 nanoparticles embedded in 3D carbonized melamine foam (CoSe2 /CMF) for Li-CO2 batteries is reported. The abundant CoSe2 clusters can not only facilitate CO2 reduction/evolution kinetics but also serve as Li2 CO3 nucleation sites for homogeneous discharge product growth. The CoSe2 /CMF-based Li-CO2 battery exhibits a large initial discharge capacity as high as 5.62 mAh cm-2 at 0.05 mA cm-2 , a remarkably small voltage gap of 0.72 V, and an ultrahigh energy efficiency of 85.9% at 0.01 mA cm-2 , surpassing most of the noble metal-based catalysts. Meanwhile, the battery demonstrates excellent cycling stability of 1620 h (162 cycles) at 0.02 mA cm-2 with an average overpotential of 0.98 V and energy efficiency of 85.4%. Theoretical investigations suggest that this outstanding performance is attributed to the suitable CO2 /Li adsorption and low Li2 CO3 decomposition energy. Moreover, flexible Li-CO2 pouch cell with CoSe2 /CMF cathode displays stable power output under different bending deformations, showing promising potential in wearable electronic devices.

Hierarchical-Pore-Stabilization Strategy for Fabricating 18.3 wt% High-Loading Single-Atom Catalyst for Oxygen Reduction Reaction.

Metal single-atom catalysts (M-SACs) attract extraordinary attention for promoting oxygen reduction reaction (ORR) with 100% atomic utilization. However, low metal loading (usually less than 2 wt%) limits their overall catalytic performance. Herein, a hierarchical-structure-stabilization strategy for fabricating high-loading (18.3%) M-SACs with efficient ORR activity is reported. Hierarchical pores structure generated with high N content by SiO2 can provide more coordination sites and facilitate the adsorption of Fe3+ through mesoporous and confinement effect of it stabilizes Fe atoms in micropores on it during pyrolysis. High N content on hierarchical pores structure could provide more anchor sites of Fe atoms during the subsequent secondary pyrolysis and synthesize the dense and accessible Fe-N4 sites after subsequent pyrolysis. In addition, Se power is introduced to modulate the electronic structure of Fe-N4 sites and further decrease the energy barrier of the ORR rate-determining step. As a result, the Fe single atom catalyst delivers unprecedentedly high ORR activity with a half-wave potential of 0.895 V in 0.1 M KOH aqueous solution and 0.791 V in 0.1 M HClO4 aqueous solution. Therefore, a hierarchical-pore-stabilization strategy for boosting the density and accessibility of Fe-N4 species paves a new avenue toward high-loading M-SACs for various applications such as thermocatalysis and photocatalysis.

Cyclic GMP is involved in auxin signalling during Arabidopsis root growth and development.

The second messenger cyclic guanosine 3',5'-monophosphate (cGMP) plays an important role in plant development and responses to stress. Recent studies indicated that cGMP is a secondary signal generated in response to auxin stimulation. cGMP also mediates auxin-induced adventitious root formation in mung bean and gravitropic bending in soybean. Nonetheless, the mechanism of the participation of cGMP in auxin signalling to affect these growth and developmental processes is largely unknown. In this report we provide evidence that indole-3-acetic acid (IAA) induces cGMP accumulation in Arabidopsis roots through modulation of the guanylate cyclase activity. Application of 8-bromo-cGMP (a cell-permeable cGMP derivative) increases auxin-dependent lateral root formation, root hair development, primary root growth, and gene expression. In contrast, inhibitors of endogenous cGMP synthesis block these processes induced by auxin. Data also showed that 8-bromo-cGMP enhances auxin-induced degradation of Aux/IAA protein modulated by the SCF(TIR1) ubiquitin-proteasome pathway. Furthermore, it was found that 8-bromo-cGMP is unable to directly influence the auxin-dependent TIR1-Aux/IAA interaction as evidenced by pull-down and yeast two-hybrid assays. In addition, we provide evidence for cGMP-mediated modulation of auxin signalling through cGMP-dependent protein kinase (PKG). Our results suggest that cGMP acts as a mediator to participate in auxin signalling and may govern this process by PKG activity via its influence on auxin-regulated gene expression and auxin/IAA degradation.