Facet Engineering of Advanced Electrocatalysts Toward Hydrogen/Oxygen Evolution Reactions

The electrocatalytic water splitting technology can generate highpurity hydrogen without emitting carbon dioxide,which is in favor of relieving environmental pollution and energy crisis and achieving carbon neutrality.Electrocatalysts can effectively reduce the reaction energy barrier and increase the reaction efficiency.Facet engineering is considered as a promising strategy in controlling the ratio of desired crystal planes on the surface.Owing to the anisotropy,crystal planes with different orientations usually feature facet-dependent physical and chemical properties,leading to differences in the adsorption energies of oxygen or hydrogen intermediates,and thus exhibit varied electrocatalytic activity toward hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In this review,a brief introduction of the basic concepts,fundamental understanding of the reaction mechanisms as well as key evaluating parameters for both HER and OER are provided.The formation mechanisms of the crystal facets are comprehensively overviewed aiming to give scientific theory guides to realize dominant crystal planes.Subsequently,three strategies of selective capping agent,selective etching agent,and coordination modulation to tune crystal planes are comprehensively summarized.Then,we present an overview of significant contributions of facet-engineered catalysts toward HER,OER,and overall water splitting.In particular,we highlight that density functional theory calculations play an indispensable role in unveiling the structure–activity correlation between the crystal plane and catalytic activity.Finally,the remaining challenges in facet-engineered catalysts for HER and OER are provided and future prospects for designing advanced facet-engineered electrocatalysts are discussed.

Environment-tolerant ionic hydrogel-elastomer hybrids with robust interfaces,high transparence,and biocompatibility for a mechanical-thermal multimode sensor

The human skin,an important sensory organ,responds sensitively to external stimuli under various harsh conditions.However,the simultaneous achievement of mechanical/thermal sensitivity and extreme environmental tolerance remains an enormous challenge for skin-like hydrogel-based sensors.In this study,a novel skin-inspired hydrogel–elastomer hybrid with a sandwich structure and strong interfacial bonding for mechanical–thermal multimode sensing applications is developed.An inner-layered ionic hydrogel with a semiinterpenetrating network is prepared using sodium carboxymethyl cellulose(CMC)as a nanofiller,lithium chloride(LiCl)as an ionic transport conductor,and polyacrylamide(PAM)as a polymer matrix.The outer-layered polydimethylsiloxane(PDMS)elastomers fully encapsulating the hydrogel endow the hybrids with improved mechanical properties,intrinsic waterproofness,and long-term water retention(>98%).The silane modification of the hydrogels and elastomers imparts the hybrids with enhanced interfacial bonding strength and integrity.The hybrids exhibit a high transmittance(~91.2%),fatigue resistance,and biocompatibility.The multifunctional sensors assembled from the hybrids realize real-time temperature(temperature coefficient of resistance,approximately1.1%℃^(-1))responsiveness,wide-range strain sensing capability(gauge factor,~3.8)over a wide temperature range(from-20℃ to 60℃),and underwater information transmission.Notably,the dualparameter sensor can recognize the superimposed signals of temperature and strain.The designed prototype sensor arrays can detect the magnitude and spatial distribution of forces and temperatures.The comprehensive performance of the sensor prepared via a facile method is superior to that of most similar sensors previously reported.Finally,this study develops a new material platform for monitoring human health in extreme environments.

Electrochemiluminescence of Bare Glassy Carbon with Benzoyl Peroxide as the Coreactant in N,N-Dimethylformamide

The electrochemiluminescence(ECL)properties of many carbon materials have been reported with glassy carbon(GC),Pt,Au or indium tin oxide(ITO)as the working electrode(WE).As one type of carbon materials,GC itself can generate ECL signal.Some research groups have already noticed the ECL signal from GC WE and reported the results of GC WE with respect to their luminophores.However,comprehensive analyses of ECL properties of GC WE are rare.Herein,the ECL properties of GC WE in organic electrolyte with benzoyl peroxide as the coreactant are reported.Our results are of great importance to distinguish the true ECL data of luminophores from that of GC.

Hierarchical porous carbon derived from one-step self-activation of zinc gluconate for symmetric supercapacitors with high energy density

Porous carbons with high specific area surfaces are promising electrode materials for supercapacitors.However,their production usually involves complex,time-consuming,and corrosive processes.Hence,a straightforward and effective strategy is presented for producing highly porous carbons via a self-activation procedure utilizing zinc gluconate as the precursor.The volatile nature of zinc at high temperatures gives the carbons a large specific surface area and an abundance of mesopores,which avoids the use of additional activators and templates.Consequently,the obtained porous carbon electrode delivers a satisfactory specific capacitance and outstanding cycling durability of 90.9%after 50000 cycles at 10 A·g^(-1).The symmetric supercapacitors assembled by the optimal electrodes exhibit an acceptable rate capability and a distinguished cycling stability in both aqueous and ionic liquid electrolytes.Accordingly,capacitance retention rates of 77.8%and 85.7%are achieved after 50000 cycles in aqueous alkaline electrolyte and 10000 cycles in ionic liquid electrolyte.Moreover,the symmetric supercapacitors deliver high energy/power densities of 49.8 W·h·kg^(-1)/2477.8 W·kg^(-1) in the Et4NBF4 electrolyte,outperforming the majority of previously reported porous carbon-based symmetric supercapacitors in ionic liquid electrolytes.

N-doped honeycomb-like porous carbon towards high-performance supercapacitor

Biomass-derived porous carbon with developed pore structure is critical to achieving high performance electrode materials.In this work,we report a grape-based honeycomb-like porous carbon(GHPC)prepared by KOH activation and carbonization,followed by N-doping(NGHPC).The obtained NGHPC exhibits a unique honeycomb-like structure with hierarchically interconnected micro/mesopores,and high specific surface area of 1268 m^2/g.As a supercapacitor electrode,the NGPHC electrode exhibits a remarkable specific capacitance of 275 F/g at 0.5 A/g in a three-electrode cell.Moreover,the NGHPC//NGHPC symmetric supercapacitor displays a high energy density of 12.6 Wh/kg,and excellent cycling stability of approximately 95.2% capacitance retention after 5000 cycles at 5 A/g.The excellent electrochemical performance of NGHPC is ascribed to its high specific surface area,honeycomb-like structure and high-content of pyrodinic-N(36.29%).It is believed that grape-based carbon materials show great potential as advanced electrode materials for supercapacitors.

Wood-derived biochar as thick electrodes for high-rate performance supercapacitors

Developing effective electrodes with commercial-level active mass-loading(>10 mg cm^(−2))is vital for the practical application of supercapacitors.However,high active mass-loading usually requires thick active mass layer,which severely hinders the ion/electron transport and results in poor capacitive performance.Herein,a self-standing biochar electrode with active mass-loading of ca.40 mg cm^(−2) and thickness of 800μm has been developed from basswood.The basswood was treated with formamide to incorporate N/O in the carbon structure,followed by mild KOH activation to ameliorate the pore size and introduce more O species in the carbon matrix.The as-prepared carbon monoliths possess well conductive carbon skeleton,abundant N/O dopant and 3D porous structure,which are favorable for the ion/electron transport and promoting capacitance performance.The self-standing carbon electrode not only exhibits the maximum areal/mass/volumetric specific capacitance of 5037.5 mF cm^(−2)/172.5 F g^(−1)/63.0 F cm^(−3) at 2 mA cm^(−2)(0.05 A g^(−1)),but also displays excellent rate performance with 76%capacitance retention at 500 mA cm^(−2)(12.5 A g^(−1))in a symmetric supercapacitor,surpassing the state-of-art biomass-based thick carbon electrode.The assembled model can power typical electron devices including a fan,a digital watch and a logo made up of 34 light-emitting diodes for a proper period,revealing its practical application potential.This study not only puts forward a commercial-level high active mass-loading electrode from biomass for supercapacitor,but also bridges the gap between the experimental research and practical application.

Characterization of natural fiber from manau rattan(Calamus manan)as a potential reinforcement for polymer-based composites

Researches on novel natural fibers in polymer-based composites will help promote the invention of novel reinforcement and expand their possible applications.Herein,in this study,novel cellulosic fibers were extracted from the stem of manau rattan(Calamus manan)by mechanical separation.The chemical,thermal,mechanical and morphological properties of manau rattan fibers were comprehensively analyzed and studied by Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)analysis,thermogravimetric analysis(TGA),single fiber tensile test and scanning electron microscopy(SEM).Component analysis re-sults showed that the cellulose,hemicellulose and lignin contents of C.manan fibers were 42wt%,20wt%,and 27wt%,respectively.The surface of the rattan fiber was hydrophilic according to the oxygen/carbon ratio of 0.49.The C.manan has a crystalline index of 48.28%,inducing a max-imum degradation temperature of 332.8°C.This reveals that it can be used as a reinforcement for thermoplastic composites whose operating temperature is below 300°C.The average ten-sile strength can reach(273.28±52.88)MPa,which is beneficial to improve the mechanical properties of rattan fiber reinforced composites.The SEM images displayed the rough surface of the fiber,which helped to enhance the interfacial adhesion between the fibers and matrices in composites.These results indicate the great potential of C.manan fibers as the reinforcement in polymer-based composites.