Ni Single Atoms Research Articles

Electronic Modulation and Symmetry-Breaking Engineering of Single-Atom Catalysts Driving Long-Cycling Li-S Battery.

Developing efficient and durable single-atom catalysts is vitally important for the sulfur redox reaction (SROR) in Li-S battery, while it remains enormous challenging. Herein, undercoordinated Ni-N3 moieties anchored on N,S-codoped porous carbon (Ni-NSC) is obtained to enhance the SROR. The experiments and theoretical calculations indicate that the symmetry-breaking charge transfer in Ni single-atom catalyst originates from tuning effect of sulfur atoms mediated Ni-N3 moieties, which can both facilitate the chemical adsorption by formation of N-Ni⋯Sn2-, and achieve a rapid redox conversion of polysulfides because of the enhanced electron transfer. As results, the Ni-NSC based Li-S battery delivers a very high initial reversible capacity (1025 mAh g-1 at 1 C), as well as outstanding cycling-stability for 2400 cycles at 2 C and 3 C, respectively. Noteworthy, the areal capacity can reach 7.8 mAh cm-2 at 0.05 C and a retention capacity of 4.7 mAh cm-2 after 100 cycles at 0.2 C for Ni-NSC based Li-S battery with sulfur loading of 5.88 mg cm-2. This work provides profound insight for rational optimizing microscopic electronic density of active site to promoting SROR in metal-sulfur batteries.

Evolution of Nitrogen-Coordinated Metal Single Atoms Toward Single-Atom Alloys on MgH₂ as Efficient and Stable Hydrogen Spillover Catalysts.

M-N-C catalysts with nitrogen-coordinated metal single-atom active sites have demonstrated high activity for hydrogen storage materials, but their stability in this application remains uncertain. This study addresses this issue by using nickel phthalocyanine (NiPc) molecules on MgH₂ particles as a model system. It is found that the N-coordinated high-valence Ni single atoms in the NiN₄ active site are unstable in the reducing environment of hydrogen storage, spontaneously evolving into zero-valence Ni, forming a Ni₁-Mg single-atom alloy (SAA). The Ni₁-Mg SAA exhibits remarkable stability in catalyzing Mg hydrogen storage reactions. Furthermore, it demonstrates comprehensive catalytic activity for each step of hydrogen absorption and desorption from Mg, surpassing the efficiency of the NiN₄ active site, especially in the critical steps of hydrogenation and dehydrogenation. Overall, the catalytic performance of Ni₁-Mg SAA is superior to most known nickel-based catalysts. This evolutionary process is also observed in FePc, CoPc, and tetraphenylporphyrin nickel (Ni-TPP), suggesting that this reducing transformation is a universal phenomenon for MN₄-type active sites in hydrogen storage catalysis.

Highly stable and electron-rich Ni single atom catalyst for directed electroreduction of CO2 to CO

Transition metal-nitrogen-carbon (M−N−C) are considered as promising candidates for the electrochemical conversion of inert CO2 into high value-added CO products. However, previous reports have focused on Ni single-atom sites (Ni SAs) and the role of Ni nanoparticles (Ni NPs) in CO2 electroreduction reaction (CO2RR) has been overlooked. Herein, we prepared a series of Ni, N-codoped porous carbon (NiNC-T, T represents the temperature) catalysts by combining Ni phthalocyanine pyrolysis and acid etching strategy, which either contain only Ni SAs or both Ni SAs and Ni NPs. Notably, the NiNC-1100 catalyst with both Ni SAs and Ni NPs exhibited 99 % CO faradaic efficiency (FECO) at −0.66 V versus reversible hydrogen electrode (vs. RHE) and FECO above 98 % over a wide potential range (−0.66 V ∼ −1.06 V). Moreover, the FECO of NiNC-1100 remained above 95 % after 100 h of continuous electrocatalysis, which was significantly superior to that of the most advanced Ni single atom electrocatalysts. The systematic characterization results showed that the introduction of Ni NPs can promote the adsorption and activation of CO2 by increasing the electron cloud density of Ni SAs, thus enhancing the CO2RR catalytic performance.

The active site of Mδ+ tailed by B (or N)-doped graphyne for nitrogen reduction reaction through DFT study

NN bond activation is one of the technical problems in the conversion of N2-to-NH3. In this work, we researched Cr, Mn, Co, Ni, Cu and Pt metal single atoms anchored on B/N-doped graphyne (M/X-GY) catalysts systematically by means of DFT. The results of Bader charge and charge density verified the charge transfers between single metal and the doped graphyne in M/X-GY catalysts. Cr (+1.001 e) and Mn (+0.800 e) exhibit higher positive valence, which is favorable for N2 adsorption. Based on the "donation and back-donation" mechanism, the energies gaps of 5σ-N2 and d-M for M=Cr, Mn and Co have the lower values of 3.01, 3.18, 3.18 eV, respectively, and the N2 adsorption energies on Cr/GY (−2.046 eV) and Mn/GY (−1.622 eV) have the more negative values. As a result, the catalyst of Cr metal atom anchored on GY is promising candidate. The substitution of B can effectively promote the activation of N2 and suppress the hydrogen evolution, while the substitution of N has the minimum ΔG*N-NH of 0.26 eV and ΔGNH3 of 0.08 eV. Compared with two different NRR pathways, the distal mechanism process is more preferential than the alternating pathway. The catalyst of Cr/N-GY has higher stability and can effectively activate N2 to generate *N2H, which can serves as promising catalysts throughout the NRR process.

Biology-Based Synthesis of Nickel Single Atoms on the Surface of Geobacter sulfurreducens as an Efficient Electrocatalyst for Alkaline Water Electrolysis.

Single-atom metal catalysts are promising electrocatalysts for water electrolysis. Nickel-based electrocatalysts have shown attractive application prospects for water electrolysis. However, synthesizing stable Ni single atoms using chemical and physical approaches remains a practical challenge. Here, a facile and precise method for synthesizing stable nickel single atoms on the surface of Geobacter sulfurreducens using a microbial-mediated extracellular electron transfer (EET) process is demonstrated. It is shown that G. sulfurreducens can effectively anchor nickel single atoms on their surface. X-ray absorption near-edge structure and Fourier-transformed extended X-ray absorption fine structure spectroscopy confirm that the nickel single atom is coordinated to nitrogen in the cytochromes. The as-synthesized nickel single atoms on G. sulfurreducens exhibit excellent bifunctional catalytic properties for alkaline water electrolysis with low overpotential (η) to achieve current density (10mAcm-2) for both hydrogen evolution reactions (η = 80mV) and oxygen evolution reaction (η = 330mV) with minimal catalyst loading of 0.0015mgNicm-2. The nickel single-atom catalyst shows long-term stability at a constant electrode potential. This synthesis method based on the EET capability of electroactive bacteria provides a simple and scalable approach for producing low-cost and highly efficient nonnoble transition metal single-atom catalysts for practical applications.

Ni Cluster-Decorated Single-Atom Catalysts Achieve Near-Unity CO2-to-CO Conversion with an Ultrawide Potential Window of ≈1.7V.

Developing efficient electrocatalysts for CO2 reduction to CO within a broad potential range is meaningful for cascade application integration. In this work, hydrogen spillover is created and utilized to cultivate a proton-rich environment via the simple thermolysis of a Ni-doped Zn coordination polymer (Zn CPs (Ni)) to create asymmetric Ni single atoms co-located with adjacent Ni nanoclusters on nitrogen-doped carbon, termed as NiNC&SA/N-C, which expedites the hydrogenation of adsorbed CO2. Therefore, the sample demonstrates near-unity CO2-to-CO conversion efficiency under pH-universal conditions in ultra-wide potential windows: -0.39 to -2.05V versus RHE with the current densities ranging from 0.1 to 1.0 A cm-2 in alkaline conditions, -0.83 to -2.40V versus RHE from 0.1 to 0.9 A cm-2 in neutral environments, and -0.98 to -2.25V versus RHE across 0.1 to 0.8 A cm-2 in acid conditions. Corresponding in situ measurements and density functional theory (DFT)calculations suggest that the enhanced H2O dissociation and more efficient hydrogen spillover on NiNC&SA/N-C (compared to NiSA/N-C) accelerate the protonation of adsorbed CO2 to form *COOH intermediates. This work emphasizes the significant role of proton spillover in CO2RR, opening novel avenues for designing high-performance catalysts applicable to various electrocatalytic processes.

Nonprecious Single Atom Catalyst for Methane Pyrolysis.

The development of a suitable catalytic system for methane pyrolysis reactions requires a detailed investigation of the activation energy of C-H bonds on catalysts, as well as their stability against sintering and coke formation. In this work, both single-metal Ni atoms and small clusters of Ni atoms deposited on titanium nitride (TiN) plasmonic nanoparticles were characterized for the C-H bond activation of a methane pyrolysis reaction using ab initio spin-polarized density functional theory (DFT) calculations. The present work shows the complete reaction pathway, including energy barriers for C-H bond activation and dehydrogenated fragments, during the methane pyrolysis reaction on catalytic systems. Interestingly, the C-H bond activation barriers were low for both Ni single-atom and Ni-clusters, showing the energy barriers of ~1.10 eV and ~0.88 eV, respectively. Additionally, single-atom Ni-TiN showed weaker binding to adsorbates, and a net endothermic reaction pathway indicated that the single-atom Ni-TiN was expected to resist coke formation on its surface. However, these Ni single-atom catalysts can sinter, aggregate into a small cluster, and form a coke layer from the highly exothermic reaction pathway that the cluster takes despite the facile reaction pathway.

Mechanistic insight into the synergy between nickel single atoms and nanoparticles on N-doped carbon for electroreduction of CO2

The synergy of single atoms (SAs) and nanoparticles (NPs) has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction (CO2RR); however, the rationalization of the SAs/NPs proportion remains one challenge for the catalyst design. Herein, a Ni2+-loaded porous poly(ionic liquids) (PIL) precursor synthesized through the free radical self-polymerization of the ionic liquid monomer, 1-allyl-3-vinylimidazolium chloride, was pyrolyzed to prepare the Ni, N co-doped carbon materials, in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing temperature. The catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO2 into CO. Operando Ni K-edge X-ray absorption near-edge structure (XANES) spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and NPs. The charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active sites. In the electroreduction of CO2, the co-existence of Ni SAs and NPs strengthened the CO2 activation and the affinity towards the key intermediate of *COOH, lowering the free energy for the potential-determining *CO2 → *COOH step, and therefore promoted the catalysis efficiency.

Nickel single-atom synergistic iron-nitrogen sites for efficient CO2 electroreduction at a wide potential range

Recently, diatomic site catalysts (DASCs) by introducing a second metal active site have become a research focus in electrochemical CO2 reduction reaction (eCO2RR), as can regulate electronic structure of metal centers and optimize reaction free energies. However, hitherto the studies on the origin of the outstanding performance of DASCs and the accurate identification of active centers are not still clear. Herein, we designed a nickel–iron diatomic site catalyst by loading highly dispersed iron phthalocyanine (FePc) on a nickel single-atom with ultrathin porous nitrogen-doped carbon nanosheet substrate (denoted as FePc/M-LNi-NC). Experimental and calculational results prove that the synergistic catalysis of FePc and carbon nanosheet based Ni single-atom endowed FePc/M-LNi-NC achieving excellent CO2 reduction performance with a maximum CO Faradaic efficiency of 98.8 % at –0.8 V vs. RHE. In particular, the current density of FePc/M-LNi-NC at −1.0 V vs. RHE in an H-type cell (−20.9 mA/cm2) is 5.6 times that of FePc (3.7 mA/cm2). Compared with M-LNi-NC, the potential range of FePc/M-LNi-NC when FECO above 95 % expands from 0.31 to 0.43 V. Density functional theory calculations reveal that the Fe site in FePc/M-LNi-NC has a lower free energy change for *COOH formation (ΔG*COOH) and CO desorption (ΔGCO) than Ni site, thus exhibits higher electrocatalytic activity. Furthermore, the ΔG*COOH on FePc/M-LNi-NC declines from 0.78 to 0.08 eV compared to M-LNi-NC, and the ΔGCO lowers from 1.36 to 0.33 eV compared to FePc, thus FePc/M-LNi-NC achieves high performance for eCO2RR at a wide potential range.

Highly Sensitive Ammonia Gas Sensors at Room Temperature Based on the Catalytic Mechanism of N, C Coordinated Ni Single-Atom Active Center

HighlightsExploiting single-atom catalytic activation and targeted adsorption properties, Ni single-atom active sites based on N, C coordination are constructed on the surface of two-dimensional MXene nanosheets (Ni–N–C/Ti3C2Tx), enabling highly sensitive and selective NH3 gas detection.The catalytic activation effect of Ni–N–C/Ti3C2Tx effectively reduces the Gibbs free energy of the sensing elemental reaction, while its electronic structure promotes the spill-over effect of reactive oxygen species at the gas–solid interface.An end-sealing passivation strategy utilizing a conjugated hydrogen bond network of the conductive polymer was employed on MXene-based flexible electrodes, effectively mitigating the oxidative degradation of MXene-based gas sensors.

Nickel-based dual single atom electrocatalysts for the nitrate reduction reaction

Electrochemical nitrate (NO3−) reduction reaction (NO3−RR) to ammonium (NH4+) or nitrogen (N2) provides a green route for nitrate remediation. However, nitrite generation and hydrogen evolution reactions hinder the feasibility of the process. Herein, dual single atom catalysts were rationally designed by introducing Ag/Bi/Mo atoms to atomically dispersed NiNC moieties supported by nitrogen-doped carbon nanosheet (NCNS) for the NO3−RR. Ni single atoms loaded on NCNS (Ni/NCNS) tend to reduce NO3− to valuable NH4+ with a high selectivity of 77.8 %. In contrast, the main product of NO3−RR catalyzing by NiAg/NCNS, NiBi/NCNS, and NiMo/NCNS was changed to N2, giving rise to N2 selectivity of 48.4, 47.1 and 47.5 %, respectively. Encouragingly, Ni/NCNS, NiBi/NCNS, and NiAg/NCNS showed excellent durability in acidic electrolytes, leading to nitrate conversion rates of 70.3, 91.1, and 93.2 % after a 10-h reaction. Simulated wastewater experiments showed that NiAg/NCNS could remove NO3− up to 97.8 % at −0.62 V after 9-h electrolysis. This work afforded a new strategy to regulate the reaction pathway and improve the conversion efficiency of the NO3−RR via engineering the dual atomic sites of the catalysts.

Theoretical study on the electrochemical CO2 reduction performance of MoS2-supported Ni single atoms with transition metal substrate doping

In the context of increasing energy issues and climate change, the development of electrochemical CO2 reduction strategies using single atom catalysts (SACs) presents a viable solution by converting CO2 into high-value-added products. Transition metal dichalcogenides (TMDs) have emerged as the main candidates for SACs in electrocatalytic CO2 reduction reaction (CO2RR) catalysts. The regulation of the second coordination sphere of SACs is known to modulate their electronic structure and catalytic behavior. This study delves into the effect of transition metal-doped substrates on SACs. We employed spin-polarization density functional theory (DFT) to design a series of Ni/TM-MoS2 monolayer MoS2 materials, with transition metals (including Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, W, Re, Os, Ir, Pt and Au) substituting the Mo atoms and anchoring single atom Ni. Among them, six Ni/TM-MoS2 catalysts doped with Mn, Fe, Co, Ru, Rh, and Ir demonstrate enhanced CO2RR activity and selectivity when compared to unmodified Ni/MoS2. The Ni/Ru-MoS2 SAC exhibits the best catalytic activity and selectivity for formic acid production, with a limiting potential (UL) of -0.06 V. The incorporation of the metal-doped substrate lowers the work function of the catalyst, facilitating electron transfer and reaction progression. Furthermore, a volcanic relationship was observed between the work function and UL. This study provides strategic insights into the design and development of SACs, highlighting the potential for future modifications and applications.

Nickel Single‐Atoms Modified Organic Anodes with Enhanced Reaction Kinetics for Stable Potassium‐Ion Batteries

AbstractThe redox‐active organic compounds including potassium 1,1′‐biphenyl‐4,4′‐dicarboxylate (K‐BPDC) are attracting considerable attention as anodes for potassium‐ion batteries (PIBs). Nevertheless, the practical applications of K‐BPDC organic anodes are severely hindered by short cycle life due to their relatively sluggish redox kinetics and instability. In this work, Ni single atoms (up to 6 wt.%) are implanted into K‐BPDC (NiSA@K‐BPDC) by using an electrochemical‐induced reconstruction (EIR) strategy to enhance the reaction kinetics and stability of PIBs. During the EIR process, Ni‐based metal‐organic framework (Ni‐BPDC) is in situ reconstructed into K‐BPDC by replacing Ni2+ with K+ to make the rest nickel species exist in the form of single atoms in K‐BPDC. By kinetic analysis and theoretical calculations, it is uncovered that the Ni single atoms supported on K‐BPDC efficiently redistribute the local charge of K‐BPDC to accelerate the K+ transport rate, and thermodynamically reduce the redox energy barrier. As a result, the NiSA@K‐BPDC anode exhibits outstanding cycle stability with 88.5% capacity retention during 4000 cycles at 1 A g−1 and an excellent rate capability (114 mAh g−1 at 2 A g−1). This study opens up a new door to the design of organic anodes with single atoms for high‐performance PIBs.

Lignin-tailored fabrication of Ni single atom catalyst with Ni-N3 active site for efficient and selective catalytic transfer hydrogenation of lignin-derived aldehydes

Developing sustainable catalytic processes for catalytic transfer hydrogenation (CTHDO) of lignin-derived aldehydes to renewable fuels and chemicals is essential for scale valorization of vast underused lignin. Herein, the work contributes to the efficient and selective vanillin (VAN) CTHDO process using formic acid (FA) as the H-donor over a novel lignin-coordinated N-anchoring Ni single-atom catalyst (Ni SAs-N@LC). Ni SAs-N@LC was fabricated through facile pyrolysis of lignin-Ni/Zn complex mixed with melamine, in which lignin localized the Ni atoms through its negatively charged groups (e.g. phenolic OH) and the dispersed Ni atoms were further anchored by the N-doped carbon support to form Ni-N3 active structure. DFT calculations revealed that the Ni-N3 structure preferentially adsorbed the –CHO end of VAN and endowed the catalyst with superior hydrogen evolution capacity. Therefore, Ni SAs-N@LC exhibited outstanding catalytic performance (98.93% of VAN conversion and 97.3% of 2-methoxy-4-methylphenol selectivity) which was significantly higher than two reference catalysts Ni NPs@LC (without N-anchoring) and Ni@C (without lignin coordination and N-anchoring) as well as the previously reported Ni-based catalysts. Moreover, Ni SAs-N@LC presented excellent feasibility to the CTHDO of a wide range of lignin-derived aldehydes and exhibited superior cycling durability in FA system owing to its acid resistance property. Consequently, this work provides a facile preparation method for atomically dispersed biomass-based catalysts and further demonstrates its favorable applicability in the CTHDO of lignin-derived aldehydes.

Metallocorroles as bifunctional electrocatalysts for water-splitting: A theoretical investigation

Designing efficient electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is an important step of the water-splitting procedure, due to the expensive electrocatalysts and the energy loss because of overpotentials. Accordingly, in the present study and based on the newly synthesized copper-corrole complexes, several metallocorroles that can be used as electrocatalysts in water-splitting reaction were theoretically designed. The main objective of the present study is to investigate the electrocatalytic behavior of various metallocorroles toward OER at the anode as well as HER at the cathode. So, our focus will be on the corrole substrates incorporating Cr, Mn, Fe, Co, Ni, and Cu single atoms, nitrogen removal defective complexes, and Cl-functionalized corroles to explore the effect of structural modifications on the catalytic activity of metallocorroles. We found that the Ni- and Cr-corrole are encouraging catalysts for the OER and HER, respectively, outperforming the synthesized copper-based substrate and other designed metallocorroles with low overpotentials (ƞOER=0.68 V and ƞHER=0.10 V). The obtained Gibbs free energies confirm the feasibility of OER on a Ni single atom and HER on a Cr single atom of metallocorroles. The Volcano diagrams also reveal that the metallocorroles with better oxygen and hydrogen desorption correspond to the Ni- and Cr-corrole substrates, respectively. Generally, results show that our designed metallocorroles can be considered competent catalysts for water-splitting reactions.

DFT study of the electrochemical CO2 reduction by Sc to Ni single atom catalysts implanted on the pristine and N-doped-H4,4,4-graphyne

The electrochemical reduction of CO2 to valuable chemicals and fuels can mitigate the energy crisis and environmental challenges. Finding the stable and efficient catalysts with high selectivity is essential for successful CO2 reduction. In this study, the catalytic activity of the transition metals (TMs) (Sc to Ni), as single-atom catalysts (SACs), on the pristine, N-doped, TM decorated and simultaneous N-doped and TM decorated H4,4,4-GY monolayers was investigated for CO2 reduction reaction (CRR) using DFT-D2 calculations. The results reveal that among three metal-free monolayers, the Nsp/H4,4,4-GY exhibits superior CO2 reduction compared to others. The investigation of CRR on TM-H4,4,4-GY, TM-Nsp/H4,4,4-GY, and TM-Nsp2/H4,4,4-GY monolayers reveals that Cr-H4,4,4-GY, Cr-Nsp/H4,4,4-GY, and Mn-Nsp2/H4,4,4-GY monolayers have the best performance among the eight TM-decorated carbon frames. The selectivity and activity of the CRR and HER for pristine and TM decorated monolayers were investigated. It was seen that the Cr-H4,4,4-GY, Cr-Nsp/H4,4,4-GY, and Cr and Mn-Nsp2/H4,4,4-GY have better catalytic activity and selectivity than other monolayers. With respect to the volcano curves, Ti-H4,4,4-GY, Co-Nsp/H4,4,4-GY, and V-Nsp2/H4,4,4-GY catalysts show superior HER catalytic activity; whereas HER does not compete with CRR for the best SACs (Cr and Mn) on the monolayers.

Design and fabrication of a novel 2D/3D ZnIn2S4@Ni1/UiO-66-NH2 heterojunction for highly efficient visible-light photocatalytic H2 evolution coupled with benzyl alcohol valorization

Making full use of photogenerated charge carriers by careful design multifunctional photocatalysts to achieving bi-value-added production with high-efficiency is highly desirable and extremely challenge. Herein, a novel 2D/3D ZnIn2S4@Ni1/UiO-66-NH2 (ZIS@Ni1/UN) heterojunction with spatially separated and precise redox sites was designed and fabricated for both photocatalytic H2 production and benzyl alcohol (BA) valorization. By precise structural regulation and modification of UiO-66 integrated with -NH2, ZnIn2S4 (ZIS) and Ni single-atom, the spatial separation of redox sites and directional electron transfer has been achieved. This realizes collaborative and efficient solar energy to chemical energy conversion. The optimal sample 5ZIS@Ni1/UN-6 shows high photocatalytic H2 and benzaldehyde (BAD) production rates of 11.44 mmol∙g−1∙h−1 and 10.02 mmol∙g−1∙h−1 under visible light. This work highlights the importance of rational construction for the engineering of charge behavior in heterogeneous photocatalysts with spatial separation and identifies their crucial role in promoting the photocatalytic redox coupling reactions.

Crystallinity modulation and microenvironment engineering synergistically manipulate ROS generation on Ni single-atom photocatalysts

The microenvironment modulation of metal-based catalysis sites plays a critical role in single-atom photocatalysis, and remains a grand challenge yet. Herein, the single-atom Ni anchored crystalline carbon nitride (Ni/CCN) nanowire arrays are reported. The obtained Ni/CCN nanowire arrays exhibit an impressive photocatalytic activity (>96% degradation of pharmaceuticals and personal care products (PPCPs) in only 5 min) and photocatalytic rate (maximum 0.5941 min−1) with only clean solar energy input. The Ni/CCN catalyst attached on microfiltration membrane in the continuous flow experiments exhibits >90% PPCPs degradation efficiency over 10 h, demonstrating the ultrahigh activity and long-term operation of the Ni/CCN catalysts. The results of electron spin resonance analysis, probe experiment and theoretical calculations demonstrate that the promoted generation of reactive oxygen species (ROS) highly relies on the crystallinity regulation and microenvironment engineering of active metal sites, which are consequently utilized to trigger the rapid degradation of PPCPs. The introduced Ni-N4 moiety disrupts the uniform distribution of delocalized electrons and precisely tunes the electronic distribution of the microenvironment in CCN, providing an electron-rich region coupled with strong electron transfer effect between Ni and adsorbed O, thus optimizing the crucial step for molecular oxygen activation. This work offers a new idea of photocatalysis from theoretical design towards broad applications through the perspective about modulating microenvironment of active metal sites and optimizing intrinsic electronic properties.

Ni Single Atom Decorated Porous Hollow Carbon Nanosphere-Based Electrodes for High Performance Symmetric Solid-State Supercapacitors.

Ni single atom containing hollow carbon nanospheres with nitrogen doping has been synthesized by carbonization of Ni(NO3)2/phloroglucinol-formaldehyde polymer/silica composite. The samples have been characterized by powder X-ray diffraction, nitrogen adsorption/desorption, electron microscopic, Raman and X-ray photoelectron spectroscopic studies. The microstructure and surface area vary with the amount of Ni(NO3)2 employed in the syntheses and the carbonization environment. An optimized amount of nickel and argon as the carbonization gas afford Ni-1.0@N@HCN-Ar which possesses overall superior features. The uniformly dispersed Ni single atoms within the hollow porous carbon framework fully utilize all the electroactive sites thereby improving the supercapacitive performance. The specific capacitance of Ni-1.0@N@HCN-Ar reaches 777 F g-1 at 1 A g-1 with a Coulombic efficiency of 98.4 % and excellent recyclability. The energy and power density of Ni-1.0@N@HCN-Ar are found to be high; at 1 A g-1 its energy density is 155.4 Wh kg-1 with a power density of 600.3 W kg-1. At a high current density of 10 A g-1 the material shows a high energy density of 118.4 Wh kg-1 with excellent power density of 6003.4 W kg-1. A symmetric solid-state supercapacitor assembled with this material, Ni-1.0@N@HCN-Ar//Ni-1.0@N@HCN-Ar using H2SO4/PVA gel electrolyte shows a superior energy density value of 30 Wh kg-1 at a power density of 1200 W kg-1.

Ethanol-assisted synthesis of a Ni single-atom catalyst with poriferous 3D framework for efficient cascade CO2 electroreduction

Ethanol-assisted synthesis of a Ni single-atom catalyst with poriferous 3D framework for efficient cascade CO2 electroreduction