Revealing component synergy of Ni‒Fe/black phosphorous composites synthesized by self-designed electrochemical method for enhancing photoelectrocatalytic oxygen evolution reaction

Developing high-activity and low-cost catalysts is the key to eliminate the limitation of sluggish anodic oxygen evolution reaction(OER)during electrocatalytic overall water splitting.Herein,Ni‒Fe/black phosphorous(BP)composites are synthesized using a simple three-electrode system,where exfoliation of bulky BP and synthesis of NiFe composites are simultaneously achieved.Under light illumination,the optimized Ni‒Fe/BP composite exhibits excellent photoelectrocatalytic OER performance(e.g.,the overpotential is 58 mV lower than a commercial RuO_(2) electrocatalyst at a current density of 10 mA·cm^(-2)).The electron transfer on this composite is proved to follow a Ni‒BP‒Fe pathway.The electronic structure of this Ni‒Fe/BP composite is effectively regulated,leading to optimized adsorption strength of the intermediate OH*and improved intrinsic activity for the OER.Together with active sites on the support,this Ni‒Fe/BP composite possesses abundant electrochemical active sites and a bug surface area for the OER.The introduction of light further accelerates the electrocatalytic OER.This work provides a novel and facile method to synthesize high-performance metal/BP composites as well as the approaches to reveal their OER mechanisms.

High-performance junction field-effect transistor based on black phosphorus/β-Ga2O3 heterostructure

Black phosphorous(BP),an excellent two-dimensional(2D)monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure,has been widely applied in various devices.As the essential building blocks for modern electronic and optoelectronic devices,high quality PN junctions based on semiconductors have attracted widespread attention.Herein,we report a junction field-effect transistor(JFET)by integrating narrow-gap p-type BP and ultra-wide gap n-typeβ-Ga2O3 nanoflakes for the first time.BP andβ-Ga2O3 form a vertical van der Waals(vdW)heterostructure by mechanically exfoliated method.The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA.More interestingly,by using the BP as the gate andβ-Ga2O3 as the channel,the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107,gate leakage current around as low as pA,maximum transconductance(gm)up to 25.3μS and saturation drain current(IDSS)of 16.5μA/μm.Moreover,it has a pinch-off voltage of–20 V and a minimum subthreshold swing of 260 mV/dec.These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.

Flat Absorber Phosphorous Black Nickel Coatings for Space Applications

A new process of flat absorber black nickel alloy coating tion from a bath containing nickel, zinc and ammonium was developed on stainless steel by electrodeposi- sulphates; thiocyanate and sodium hypophosphite for space applications. Coating process was optimized by investigating the effects of plating parameters, viz concentration of bath constituents, current density, temperature, pH and plating time on the optical properties of the black deposits. Energy dispersive X-ray spectroscopy showed the inclusion of about 6% phosphorous in the coating. The scanning electron microscopy studies revealed the amorphous nature of the coating. The corrosion resistance of the coatings was evaluated by the electrochemical impedance spectroscopy （EIS） and linear polarization （LP） techniques. The results revealed that, phosphorous addition confers better corro- sion resistance in comparison to conventional black nickel coatings. The black nickel coating obtained from hypophosphite bath provides high solar absorptance （αs） and infrared emittance （εIR） of the order of 0.93. Environmental stability to space applications was established by the humidity and thermal cycling tests.

Tuning photoresponse of graphene-black phosphorus heterostructure by electrostatic gating and photo-induced doping

Metal-semiconductor diodes constructed from two-dimensional(2D)van der Waals heterostructures show excellent gate electrostatics and a large built-in electric field at the tunnel junction,which can be exploited to make highly sensitive photodetector.Here we demonstrate a metal-semiconductor photodiode constructed by the monolayer graphene(Gr)on a few-layer black phosphorus(BP).Due to the presence of a built-in potential barrier(~0.09±0.03 eV)at the Gr-BP interface,the photoresponsivity of the Gr-BP device is enhanced by a factor of 672%,and the external quantum efficiency(EQE)increases to648%from 84%of the bare BP.Electrostatic gating allows the BP channel to be switched between p-type and n-type conduction.We further demonstrate that excitation laser power can be used to control the current polarity of the Gr-BP device due to photon-induced doping.The versatility of the Gr-BP junctions in terms of electrostatic bias-induced or light-induced switching of current polarity is potentially useful for making dynamically reconfigurable digital circuits.

Electrically Stimulated Band Alignment Transit in Black Phosphorus/β-Ga2O3 Heterostructure Dual-band Photodetector

In recent decades,dual-band photodetectors have received widespread attention due to better target iden-tification,which are considered as the development trend of next generation photodetectors.However,the traditional dual-band photodetectors based on heteroepitaxial growth,superlattice and multiple quantum well structures are limited by complex fabrication process and low integration.Herein,we report a UV/IR dual-band photodetector by integrating ultra-wide gap B-Ga2O,and narrow-gap black phosphorous(BP)nanoflakes.A vertical van der Waals(vdW)heterostructure is formed between BP and B-Ga,O,by mechanically exfoliated method integrated without the requirement of lattice match.The heterostructure devices show excellent rectification characteristics with high recti-fving ratio of ca.10 and low reverse current around pA.Moreover,the device displays obvious photoresponse underUV and IR irradiations with responsivities of 0.87 and 2.15 mA/W,respectively.We also explore the band alignment transit within the heterostructure photodetector at different bias voltages.This work paves the way for fabricating novel dual-band photodetectors by utilizing 2D materials.