Impacts of hydrogen annealing on the carrier lifetimes in p-type 4H-SiC after thermal oxidation

Thermal oxidation and hydrogen annealing were applied on a 100μm thick Al-doped p-type 4H-Si C epitaxial wafer to modulate the minority carrier lifetime,which was investigated by microwave photoconductive decay(μ-PCD).The minority carrier lifetime decreased after each thermal oxidation.On the contrary,with the hydrogen annealing time increasing to3 hours,the minority carrier lifetime increased from 1.1μs(as-grown)to 3.14μs and then saturated after the annealing time reached 4 hours.The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes.Moreover,the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed.The average minority carrier lifetime was up to 1.94μs and non-uniformity of carrier lifetime reached 38%after 4-hour hydrogen annealing.The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms.

Multicomponent transition metal phosphide for oxygen evolution

Transition metal phosphides(TMPs)have exhibited decent performance in an oxygen evolution reaction(OER),which is a kinetic bottleneck in many energy storages and conversion systems.Most reported catalysts are composed of three or fewer metallic components.The inherent complexity of multicomponent TMPs with more than four metallic components hinders their investigation in rationally designing the structure and,more importantly,comprehending the component-activity correlation.Through hydrothermal growth and subsequent phosphor-ization,we reported a facile strategy for combining TMPs with tunable elemental compositions(Ni,Fe,Mn,Co,Cu)on a two-dimensional ti-tanium carbide(MXene)flake.The obtained TMPs/MXene hybrid nanostructures demonstrate homogeneously distributed elements.They ex-hibit high electrical conductivity and strong interfacial interaction,resulting in an accelerated reaction kinetics and long-term stability.The res-ults of different component catalysts’OER performance show that NiFeMnCoP/MXene is the most active catalyst,with a low overpotential of 240 mV at 10 mA·cm−2,a small Tafel slope of 41.43 mV·dec−1,and a robust long-term electrochemical stability.According to the electrocata-lytic mechanism investigation,the enhanced NiFeMnCoP/MXene OER performance is due to the strong synergistic effect of the multi-ele-mental composition.Our work,therefore,provides a scalable synthesis route for multi-elemental TMPs and a valuable guideline for efficient MXene-supported catalysts design.

Identification of Mulberry Endophytic Fungus Macrophomina phaseolina Strain

An endophytic fungus MOD-1 was isolated from the roots of mulberry trees,and was identified as Macrophomina phaseolina by morphology and molecular biology.The 5.8 S rDNA/ITS region sequence of the strain has been registered in GeneBank with the accession number of EU250575.

Synergistic phosphorized NiFeCo and MXene interaction inspired the formation of high-valence metal sites for efficient oxygen evolution

Exploring low-cost,high-performance,and stable electrocatalysts toward the oxygen evolution reaction(OER)is highly desired but remains challenging.Transition metal hydroxide has been wildly utilized as a promising candidate,but practical implementation is impeded by insufficient catalytic activity,easy agglomeration,and poor conductivity.Here,we report that both phosphorization and combination with MXnene can improve the catalysts’intrinsic activity and conductivity.Besides,MXene also prevents the agglomeration of the nanoparticles,resulting in the enhanced exposure of active sites.Experimental char-acterizing and density functional theory simulations revealed that P species can attract electrons to pro-mote the formation of high-valence states of adjacent metal atoms,and coupling MXene support can effectively modulate the electronic structure and optimize the d-band center,which boosts the OER per-formance.Consequently,the optimized NiFeCoP/Mxene catalyst exhibits a low overpotential of 240 mV at a current density of 10 mA cm^(−2),a small Tafel slope of 55 mV dec^(−1),and superior long-term stability of 40 h in 1 M KOH electrolyte,which is superior to other counterparts.