Covalently Bonded Ni Sites in Black Phosphorene with Electron Redistribution for Efficient Metal‑Lightweighted Water Electrolysis

The metal-lightweighted electrocatalysts for water splitting are highly desired for sustainable and economic hydrogen energy deployments,but challengeable.In this work,a low-content Ni-functionalized approach triggers the high capability of black phosphorene(BP)with hydrogen and oxygen evolution reaction(HER/OER)bifunctionality.Through a facile in situ electro-exfoliation route,the ionized Ni sites are covalently functionalized in BP nanosheets with electron redistribution and controllable metal contents.It is found that the as-fabricated Ni-BP electrocatalysts can drive the water splitting with much enhanced HER and OER activities.In 1.0 M KOH electrolyte,the optimized 1.5 wt%Nifunctionalized BP nanosheets have readily achieved low overpotentials of 136 mV for HER and 230 mV for OER at 10 mA cm^(−2).Moreover,the covalently bonding between Ni and P has also strengthened the catalytic stability of the Ni-functionalized BP electrocatalyst,stably delivering the overall water splitting for 50 h at 20 mA cm^(−2).Theoretical calculations have revealed that Ni–P covalent binding can regulate the electronic structure and optimize the reaction energy barrier to improve the catalytic activity effectively.This work confirms that Ni-functionalized BP is a suitable candidate for electrocatalytic overall water splitting,and provides effective strategies for constructing metal-lightweighted economic electrocatalysts.

Interface and M^(3+)/M^(2+)Valence Dual-Engineering on Nickel Cobalt Sulfoselenide/Black Phosphorus Heterostructure for Efficient Water Splitting Electrocatalysis

The catalyst innovation that aims at noble-metal-free substitutes is one key aspect for future sustainable hydrogen energy deployment.In this paper,a nickel cobalt sulfoselenide/black phosphorus heterostructure(NiCoSe|S/BP)was fabricated to realize the highly active and durable water electrolysis through interface and valence dual-engineering.The NiCoSe|S/BP nanostructure was constructed by in-situ growing NiCo hydroxide nanosheet arrays on few-layer BP and subsequently one-step sulfoselenization by SeS2.Besides the conductive merit of BP substrate,holes in p-type BP are capable of oxidizing the Co^(2+)to high-valence and electron-accepting Co^(3+),benefiting the oxygen evolution reaction(OER).Meanwhile,Ni^(3+)/Ni^(2+)ratio in the heterostructure is reduced to maintain the electrical neutrality,which corresponds to the increased electron-donating character for boosting hydrogen evolution reaction(HER).As for HER and OER,the heterostructured NiCoSe|S/BP electrocatalyst exhibits small overpotentials of 172 and 285 mV at 10 mA cm^(-2)(η_(10))in alkaline media,respectively.And overall water splitting has been achieved at a low cell potential of 1.67 V at η_(10) with high stability.Molecular sensing and density functional theory(DFT)calculations are further proposed for understanding the rate-determine steps and enhanced catalytic mechanism.The investigation presents a deep-seated perception for the electrocatalytic performance enhancement of BP-based heterostructure.

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives

Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world’s carbon neutrality and future sustainable eco-society.Water-splitting is a constructive technology for unpolluted and high-purity H2 production,and a series of non-precious electrocatalysts have been developed over the past decade.To further improve the catalytic activities,metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting(e-DA)properties,while for anion doping,the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances.In this review,we summarize the recent developments of the many different anion-mixed transition metal compounds(e.g.,nitrides,halides,phosphides,chalcogenides,oxyhydroxides,and borides/borates)for efficient water electrolysis applications.First,we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions.Furthermore,some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis.The rationales behind their enhanced electrochemical performances are discussed.Last but not least,the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.

Optimizing interfacial electronic coupling with metal oxide to activate inert polyaniline for superior electrocatalytic hydrogen generation

Tuning and optimization of electronic structures and related reaction energetics are critical toward the rational design of efficient electrocatalysts.Herein,experimental and theoretical calculation demonstrate the originally inert N site within polyaniline(PANI)can be activated for hydrogen evolution by proper d-πinterfacial electronic coupling with metal oxide.As a result,the assynthesized WO3 assemblies@PANI via a facile redox-induced assembly and in situ polymerization,exhibits the electrocatalytic production of hydrogen better than other control samples including W18O49@PANI and most of the reported nobel-metal-free electrocatalysts,with low overpotential of 74 mV at 10 mA·cm−2 and small Tafel slope of 46 mV·dec−1 in 0.5M H2SO4(comparable to commercial Pt/C).The general efficacy of this methodology is also validated by extension to other metal oxides such as MoO3 with similar improvements.

Suppression of Sn^(2+) and Lewis acidity in SnS_(2)/black phosphorus heterostructure for ppb-level room temperature NO_(2) gas sensor

The selective detection of harmful gases is of great significance to human health and air quality,triggering the need for special customizations of sensing material structure.In this study,we prepared a novel Sn S_(2)/black phosphorus(BP)two-dimensional(2D)-2D heterostructure via the in situ hydrothermal growth of Sn S_(2)nanosheets on exfoliated BP lamellae for NO_(2)sensing applications.In the Sn S_(2)/BP composite,the holes with high oxidizability in p-type BP could oxidize Sn^(2+)into Sn^(4+),thus inhibiting the formation of Lewis acidic S vacancies.This Sn^(2+)/Lewis acidity suppression of the composite was further confirmed by X-ray photoelectron spectroscopy and acidic double-layer capacitance analyses,and promoted the adsorption and detection of acidic NO_(2).Owing to its valence and Lewis acidity engineering,the Sn S_(2)/BP heterostructure sensor could detect trace levels of NO_(2)as low as 100 ppb(parts per billion)with high response,fast response/recovery,good stability,and selectivity at room temperature.The high absorption energy of NO_(2)(à0.74 e V),as indicated by the density functional theory calculations,suggests that NO_(2)was chemically adsorbed on the Sn S_(2)/BP surface,which was also evidenced by the in situ Raman spectroscopy results.This work opens up interesting opportunities for the rational design of highly efficient NO_(2)gas sensors through Lewis acidity modification and interface engineering.

Recent progress on the long-term stability of hydrogen evolution reaction electrocatalysts

Developing new methodologies to produce clean and renewable energy resources is pivotal for carbon-neutral initiatives.Hydrogen(H2)is considered as an ideal energy resource due to its nontoxic,pollution-free,high utilization rate,and high calorific combustion value.Electrolysis of water driven by the electricity generated from renewable and clean energy sources(e.g.,solar energy,wind energy)to produce hydrogen attracts great efforts for hydrogen production with high purity.Recently,the breakthrough of the catalyst activity limit for the hydrogen evolution reaction(HER)catalysts has received extensive attention.Comparatively,fewer reviews have focused on the long-term stability of HER catalysts,which is indeed decisive for large-scale electrolytic industrialization.Therefore,a systematic summary concentrated on the durability of HER electrocatalysts would provide a fundamental understanding of the electrocatalytic performance for practical applications and offer new opportunities for the rational design of the highly performed HER electrocatalysts.This review summarizes the research progress toward the HER stability of precious metals,transition metals,and metal-free electrocatalysts in the past few years.It discusses the challenges in the stability of HER electrocatalysts and the future perspectives.We anticipate that it would provide a valuable basis for designing robust HER electrocatalysts.

Hydrogenated vanadium oxides as an advanced anode material in lithium ion batteries

Current research on vanadium oxides in lithium ion batteries （LIBs） considers them as cathode materials, whereas they are rarely studied for use as anodes in LIBs because of their low electrical conductivity and rapid capacity fading. In this work, hydrogenated vanadium oxide nanoneedles were prepared and incorporated into freeze-dried graphene foam. The hydrogenated vanadium oxides show greatly improved charge-transfer kinetics, which lead to excellent electrochemical properties. When tested as anode materials （0.005-3.0 V vs. Li/Li＋） in LIBs, the sample activated at 600℃ exhibits high specific capacity （-941 mA-h-g-1 at 100 mA.g-1） and high-rate capability （-504 mA·h·g-1 at 5 A·g-1）, as well as excellent cycling performance （-285 mA.h.g-1 in the 1,000th cycle at 5A-g-1）. These results demonstrate the promising application of vanadium oxides as anodes in LIBs.

High-entropy alloys and compounds for electrocatalytic energy conversion applications

High-entropy materials,composed of five or more elements in near-equiatomic percentage,have been attracting tremendous interests due to their advantageous properties in a variety of applications.Recently,electrocatalysis on high-entropy alloys(HEAs)and high-entropy compounds(HECs)has emerged as a new and promising material owing to the tailored composition and the disordered con-figuration of HEAs and HECs.Though extensive efforts have been devoted to investigating the catalytic nature of HEAs and HECs,the details related to the active sites and intrinsic activity of such catalysts still remain uncertain due to the complexity of the multicomponent systems.In this review,the recent progress of HEAs and HECs is systematically reviewed in terms of their synthetic strate-gies and electrocatalytic applications.Importantly,the computationally assisted methods(e.g.,density functional theory[DFT])are also presented to discover and design the optimumHEA-andHEC-based catalysts.Subsequently,the appli-cations of HEAs and HECs in electrocatalytic energy conversion reactions will be discussed,including hydrogen evolution reaction,oxygen evolution reaction,oxygen reduction reaction,carbon dioxide reduction reaction,nitrogen reduction reaction,methanol oxidation reaction,and ethanol oxidation reaction(EOR).Moreover,the prospects and future opportunities for this research field are cau-tiously discussed.A series of upcoming challenges and questions are thoroughly proposed from the experimental and theoretical aspects as well as other future applications in electrocatalysis.