Precisely Control Relationship between Sulfur Vacancy and H Absorption for Boosting Hydrogen Evolution Reaction

Ef fective and robust catalyst is the core of water splitting to produce hydrogen.Here, we report an anionic etching method to tailor the sulfur vacancy(VS) of NiS_(2) to further enhance the electrocatalytic performance for hydrogen evolution reaction(HER). With the VS concentration change from 2.4% to 8.5%, the H* adsorption strength on S sites changed and NiS_(2)-VS 5.9% shows the most optimized H* adsorption for HER with an ultralow onset potential(68 m V) and has long-term stability for 100 h in 1 M KOH media. In situ attenuated-total-reflection Fourier transform infrared spectroscopy(ATR-FTIRS) measurements are usually used to monitor the adsorption of intermediates. The S-H* peak of the Ni S_(2)-VS 5.9% appears at a very low voltage, which is favorable for the HER in alkaline media. Density functional theory calculations also demonstrate the Ni S_(2)-VS 5.9% has the optimal |ΔG^(H*)| of 0.17 e V. This work offers a simple and promising pathway to enhance catalytic activity via precise vacancies strategy.

Surface chlorine doped perovskite‐type cobaltate lanthanum for water oxidation

Rationally manipulating the in‐situ formed catalytically active surface of catalysts remains a great challenge for a highly efficient water electrolysis.Here,we report a cationic oxidation method which can adjust the leaching of the in‐situ catalyst and promote the reconstruction of dynamic surface for the oxygen evolution reaction(OER).The chlorine doping can reduce the possibility of triggering in‐situ cobalt oxidation and chlorine leaching,leading to a transformation of the surface chlorine doped LaCoO_(3)(Cl‐LaCoO_(3))into an intricate amorphous(oxygen)hydroxide phase.And thus,Cl‐LaCoO_(3)nanocrystals shows an ultralow overpotential of 342 mV at the current density of 10 mA cm^(–2)and Tafel slope of 76.2 mV dec–1.Surface reconstructed Cl‐LaCoO_(3)is better than many of the most advanced OER catalysts and has proven significant stability.This work provides a new prospect for designing a high‐efficiency electrocatalyst with optimized perovskite‐structure in renewable energy system.

High-Effi ciency Catalytic Interface IrO x/CeO_(2)with Adsorbate Evolution Mechanism Boosts Oxygen Evolution Reaction in Acid Media

Oxygen evolution reaction(OER)in acid media has been intensively studied recently for its important role in proton exchange membrane electrolyzers.CeO_(2)-based nanomaterials have been widely used in various applications for their redox properties,oxygen vacancy,and surface activity.CeO_(2)-based nanocatalysts also exhibit superior catalytic performance in OER in acid media.Herein,we fabricated a highly effi cient catalytic interface between IrO x and CeO_(2)(IrO x/CeO_(2)),which showed a boosting OER activity with an overpotential of 217 mV at the current density of 10 mA/cm 2 and long-term stability for 10 h in 0.5 mol/L H_(2)SO_(4),which were better than those of many reported catalysts.The in situ diff erential electrochemical mass spectrometry results demonstrated that IrO x/CeO_(2)and the commercial IrO 2(IrO 2-com)followed the adsorbate evolution mechanism,whereas the pure CeO_(2)surface followed the lattice oxygen oxidation mechanism under the same conditions for OER.These indicated that the interface of IrO x and CeO_(2)improved mass transfer effi ciency and reactivity,which also prevented the lattice oxygen evolution in the CeO_(2)structure and protected the whole structure.This work fi nds a new way for OER in acid media catalyzed by CeO_(2)-based nanocatalysts and promotes the design strategy for other CeO_(2)-based nanostructures.

Bimetallic Nickel Cobalt Sulfide as E cient Electrocatalyst for Zn–Air Battery and Water Splitting

The development of e cient earth-abundant electrocatalysts for oxygen reduction, oxygen evolution, and hydrogen evolution reactions(ORR, OER, and HER) is important for future energy conversion and energy storage devices, for which both rechargeable Zn–air batteries and water splitting have raised great expectations. Herein, we report a single-phase bimetallic nickel cobalt sulfide((Ni,Co)S_2) as an e cient electrocatalyst for both OER and ORR. Owing to the synergistic combination of Ni and Co, the(Ni,Co)S_2 exhibits superior electrocatalytic performance for ORR, OER, and HER in an alkaline electrolyte, and the first principle calculation results indicate that the reaction of an adsorbed O atom with a H_2O molecule to form a *OOH is the potential limiting step in the OER. Importantly, it could be utilized as an advanced air electrode material in Zn–air batteries, which shows an enhanced charge–discharge performance(charging voltage of 1.71 V and discharge voltage of 1.26 V at 2 mA cm^(-2)), large specific capacity(842 mAh g_(Zn)^(-1) at 5 mA cm^(-2)), and excellent cycling stability(480 h). Interestingly, the(Ni,Co)S_2-based Zn–air battery can e ciently power an electrochemical water-splitting unit with(Ni,Co)S_2 serving as both the electrodes. This reveals that the prepared(Ni,Co)S_2 has promising applications in future energy conversion and energy storage devices.

Synthesis of silk-like FeS_2/NiS_2 hybrid nanocrystals with improved reversible oxygen catalytic performance in a Zn-air battery

The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal‐air battery devices.Herein,an efficient liquid exfoliation strategy was designed for producing silk‐like FeS2/NiS2 hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn‐air batteries.Because of the unique silk‐like morphology and interface nanocrystal structure,they can catalyze the oxygen evolution reaction(OER)efficiently with a low overpotential of 233 mV at j=10 mA cm?2.This is an improvement from the recently reported catalysts in 1.0 M KOH.Meanwhile,the oxygen reduction reaction(ORR)activity of the silk‐like FeS2/NiS2 hybrid nanocrystals showed an onset potential of 911 mV and a half‐wave potential of 640 mV.In addition,the reversible oxygen electrode activity of the silk‐like FeS2/NiS2 hybrid nanocrystals was calculated to be 0.823 V,based on the potential of the OER and ORR.Further,the homemade rechargeable Zn‐air batteries using FeS2/NiS2 hybrid nanocrystals as the air‐cathode displayed a high open‐circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h.The solid Zn‐air batteries exhibited an excellent rechargeable performance for 15 h.This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.

Construction of surface lattice oxygen in metallic N-CuCoS1.97 porous nanowire for wearable Zn-air battery

Achieving high activity and stability oxygen evolution reaction(OER) catalysts to optimize the efficiency of metal-air battery, water splitting and other energy conversion devices, remains a formidable challenge.Herein, we demonstrate the metallic porous nanowires arrays with abundant defects via nitrogen and copper codoped CoS1.97 nanowires(N-CuCoS1.97 NWs). The N-CuCoS1.97 NWs can serve as an excellent OER self-supported electrode with an overpotential of 280 mV(j = 10 m A cm-2) and remarkable long-term stability. The X-ray absorption near-edge structure(XANES) and X-ray photoelectron spectrum(XPS) measurements confirmed the surface lattice oxygen created on the N-CuCoS1.97 NWs during OER. Then, the density function theory(DFT) results evident that lattice oxygen constructed surface of N-CuCoS1.97 NWs has more favorable OER energetic profiles and absorption for reaction intermediate. More importantly,the flexible and wearable Zn-air battery fabricated by the N-CuCoS1.97 NWs shows excellent rechargeable and mechanical stability, which can be used in portable mobile device.

Applications of Rare Earth Promoted Transition Metal Sulfides in Electrocatalysis

With the rapid consumption of fossil fuels and the resulting environmental problems,researchers are working to find sustainable alternative energy and energy storage and conversion methods.Transition metal sulfur compounds have attracted extensive attention due to their excellent electrical conductivity,low cost,adjustable components and good electrocatalytic performance.As an alternative to noble metal catalysts,they have emerged as a promising electrocatalyst.However,their low catalytic activity and poor stability limit their large-scale practical applications.Rare earth elements,known as industrial vitamins,are widely used in various fields due to their special redox properties,oxygen affinity and electronic structure.Therefore,the construction of rare earth promoted transition metal sulfides is of far-reaching significance for the development of catalysts.Here,we review the applications of various rare earth promoted transition metal sulfides in energy storage and conversion in recent years,which focuses on three ways in rare earth promoted transition metal sulfide,including doping,interfacial modification engineering and structural facilitation.As well,these materials are used in electrochemical reactions such as OER,HER,ORR,CO_(2)RR,and so on,in order to explore the important role of rare earth in the field of electrocatalysis,the future challenges and opportunities.

Ruthenium-modified porous NiCo2O4 nanosheets boost overall water splitting in alkaline solution

Exploring efficient oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)electrocatalysts is crucial for developing water splitting devices.The composition and structure of catalysts are of great importance for catalytic performance.In this work,a heterogeneous Ru modified strategy is engineered to improve the catalytic performance of porous NiCo_(2)O_(4)nanosheets(NSs).Profiting from favorable elements composition and optimized structure property of decreased charge transfer barrier,more accessible active sites and increased oxygen vacancy concentration,the Ru-NiCo_(2)O_(4)NSs exhibits excellent OER activity with a low overpotential of 230 mV to reach the current density of 10 mA/cm^(2)and decent durability.Furthermore,Ru-NiCo_(2)O_(4)NSs show superior HER activity than the pristine NiCo_(2)O_(4)NSs,as well.When assembling Ru-NiCo_(2)O_(4)NSs couple as an alkaline water electrolyzer,a cell voltage of 1.60 V can deliver the current density of 10 mA/cm^(2).This work provides feasible guidance for improving the catalytic performance of spinel-based oxides.

Atomic-level correlation between the electrochemical performance of an oxygen-evolving catalyst and the effects of CeO_(2) functionalization

Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Comparative electrochemical studies were carried out.Onset potential,overpotential,and Tafel slope point to the superior oxygen-evolving performance of CeO_(2)-FeCo LDH with respect to FeCo LDH,therefore,demonstrating the merits of CeO_(2)functionalization.The electronic structures of Fe,Co,and Ce were analyzed by X-ray photoelectron spectroscopy(XPS)and electron energy loss spectroscopy(EELS)from which the increase of Co^(3+)and the concurrent lowering of Ce^(4+)were established.With the use of CeO_(2)-FeCo LDH,accelerated formation at a sizably reduced potential of Co-OOH,one of the key intermediates preceding the release of O_(2)was observed by in situ Raman spectroscopy.We now have the atomic-level and location-specific evidence,the increase of the active Co^(3+)across the interface to correlate the enhanced catalytic performance with CeO_(2)functionalization.

Construction and Application of Interfacial Inorganic Nanostructures

Interfacial nanostructured materials have stimulated extensive interests in the research areas of green energy production and conversion due to their unique structures and performance.These interfacial crystalline structures with rich intrinsic defects,such as oxygen vacancies,adatoms,grain bounda-ries,and substitutional impurities,have led to unique activities in a variety of catalytic reactions.The rational design and engineering development of the interfaces provide an attractive way to optimize the catalytic performance and finally improve the efficiency of energy conversion and storage.Herein,a comprehensive overview of interfacial inorganic nanostructures and their electrocatalytic applications are summarized,and some future challenge and opportunity have also been proposed.