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Single-atom catalysts (SACs) with high catalytic activity as well as great stability are demonstrating great promotion in electrocatalytic energy conversion, which is also a big challenge to achieve. Herein, we proposed a facile synthetic strategy to construct nickel-iron bimetallic hydroxide nanoribbon stabilized single-atom iridium catalysts (Ir-NiFe-OH), where the nickel-iron hydroxide nanoribbon not only can serve as good electronic conductor, but also can well stabilize and fully expose single-atom sites. Adopted as catalyst for urea oxidation reaction (UOR), it exhibited excellent UOR performance that it only needed a low operated potential of 1.38 V to achieve the current density of 100 mA·cm−2. In-situ Fourier transform infrared spectroscopy, X-ray absorption spectrum, and density functional theory calculations proved that Ir species are active centers and the existence of both Ni and Fe in the local structure of Ir atom can optimize the d-band center of Ir species, promoting the adsorption of intermediates and desorption of products for UOR. The hydrogen evolution reaction (HER)/UOR electrocatalytic cell demanded voltages of 1.46 and 1.50 V to achieve 50 and 100 mA·cm−2, respectively, which demonstrated a higher activity and better stability than those of conventional catalysts. This work opens a new avenue to develop catalysts for UORs with boosted activity and stability. [ABSTRACT FROM AUTHOR]

Electrocatalytic CO2 reduction (CO2ER) to valuable chemicals, for example, HCOOH have received widespread attention, which still suffers from moderate Faradaic efficiency with low current regarding the wide industrial application of HCOOH. Herein, we employed a strategy of modifying electronic metal‐support interaction (EMSI) by fabricating Bi nanoparticles supported Ni‐modified Bi2O2CO3 (Bi/Ni‐BOC) heterostructure. The obtained Bi/Ni‐BOC exhibited high formate Faradic efficiency (FEHCOOH) of 97% at −2.1 V (vs. Ag/AgCl) and above 90% within broad potential range (−1.7 to −2.2 V) in flow cell with superior stability at high current density of ~220 mA cm−2, and formate concentration can reach 2.4 mmol h−1 cm−2 at −2.3 V. In/ex situ x‐ray absorption fine structure (XAFS) and density functional theory (DFT) calculation indicated that Ni doping promoted the enhancement of EMSI, which improved the generation and stable existence of electron‐rich Bi to boost CO2 activation and *OHCO hydrogenation, thus facilitating highly‐efficient formate production with hydrogen evolution reaction (HER) inhibition. [ABSTRACT FROM AUTHOR]

Understanding the correlation between the structural evolution of electrocatalysts and their catalytic activity is both essential and challenging. In this study, we investigate this correlation in the context of the oxygen evolution reaction (OER) by examining the influence of structural disorder during and after dynamic structural evolution on the OER activity of Fe−Ni (oxy)hydroxide catalysts using operando X‐ray absorption spectroscopy, alongside other experiments and theoretical calculations. The Debye–Waller factors obtained from extended X‐ray absorption fine structure analyses reflect the degree of structural disorder and exhibit a robust correlation with the intrinsic OER activities of the electrocatalysts. The enhanced OER activity of in situ‐generated metal (oxy)hydroxides derived from different pre‐catalysts is linked to increased structural disorder, offering a promising approach for designing efficient OER electrocatalysts. This strategy may inspire similar investigations in related electrocatalytic energy‐conversion systems. [ABSTRACT FROM AUTHOR]

Electrocatalytic acetylene semi-hydrogenation to ethylene powered by renewable electricity represents a sustainable pathway, but the inadequate current density and single-pass yield greatly impedes the production efficiency and industrial application. Herein, we develop a F-modified Cu catalyst that shows an industrial partial current density up to 0.76 A cm−2 with an ethylene Faradic efficiency surpass 90%, and the maximum single-pass yield reaches a notable 78.5%. Furthermore, the Cu-F showcase the capability to directly convert acetylene into polymer-grade ethylene in a tandem flow cell, almost no acetylene residual in the production. Combined characterizations and calculations reveal that the Cuδ+ (near fluorine) enhances the water dissociation, and the generated active hydrogen are immediately transferred to Cu0 (away from fluorine) and react with the locally adsorbed acetylene. Therefore, the hydrogen evolution reaction is surpassed and the overall acetylene semi-hydrogenation performance is boosted. Our findings provide new opportunity towards rational design of catalysts for large-scale electrosynthesis of ethylene and other important industrial raw. Efficient electroreduction of acetylene to ethylene is crucial for industrial applications. Here, the authors reported fluorine modified copper for direct conversion of acetylene to polymer-grade ethylene in one single-pass with industrial-current-density. [ABSTRACT FROM AUTHOR]

Exploring efficient transition-metal-based electrocatalysts for oxygen evolution reaction (OER) is imperative but remain challenging for sustainable energy storage and conversion systems. Foreign species doping is a significant regulation strategy to enhance the intrinsic activity of host matrix. However, the potential relationship of structure-activity caused by guest doping elements is seldom tracked systematically. In this case, both theoretical screening and experimental verification are complementarily employed to investigate the guest doping effects of ten first-row transition metals (Sc~Zn) on bimetallic NiCo layered double hydroxide (NiCo-LDH). As a result, the optimized Fe-doped NiCo-LDH is identified as the most promising candidate toward alkaline electrocatalytic OER, which exhibits the quasi-industrial current density of 1000 mA cm-2 at overpotential of400 mV. Meanwhile, it also shows impressively long-term stability of 500 h at 500 mA cm-2 with a negligible activity loss. Moreover, in situ electrochemical Raman spectroscopy unveils the dynamic structure evolution from pre-catalytic state (Fe-NiCo-LDH) to metal oxyhydroxide (Fe-(NiCo)OOH) during the oxidation reaction, and ab-initio molecular dynamics simulations are further performed to confirm the thermodynamic stability of activated Fe-(NiCo)OOH phase. This work provides a promising platform for exploring the critical role of transition metal guest doping on host matrix in developing industrially required OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Highlights: Oxygen-coordinated single-atom Mn catalyst was fabricated via introducing oxygen functional groups rich bacterial cellulose as the adsorption regulator through a combined impregnation–pyrolysis–etching synthetic route. Mn–O–C as the electrocatalyst exhibits superior electrocatalytic activity toward ammonia synthesis with a maximum NH3 yield rate of 1476.9 ± 62.6 μg h−1 cm−2 at − 0.7 V (vs. RHE) and a faradaic efficiency of 89.0 ± 3.8% at − 0.5 V (vs. RHE) under ambient conditions. Electrocatalytic mechanism of Mn–(O–C2)4 site for nitrate reduction reaction is unveiled by a combination of in situ spectroscopy characterization and computational study. Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection. Here, we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen (O) coordination on bacterial cellulose-converted graphitic carbon (Mn–O–C). Evidence of the atomically dispersed Mn–(O–C2)4 moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy. As a result, the as-synthesized Mn–O–C catalyst exhibits superior NitRR activity with an NH3 yield rate (RNH3) of 1476.9 ± 62.6 μg h−1 cm−2 at − 0.7 V (vs. reversible hydrogen electrode, RHE) and a faradaic efficiency (FE) of 89.0 ± 3.8% at − 0.5 V (vs. RHE) under ambient conditions. Further, when evaluated with a practical flow cell, Mn–O–C shows a high RNH3 of 3706.7 ± 552.0 μg h−1 cm−2 at a current density of 100 mA cm−2, 2.5 times of that in the H cell. The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn–(O–C2)4 sites not only effectively inhibit the competitive hydrogen evolution reaction, but also greatly promote the adsorption and activation of nitrate (NO3−), thus boosting both the FE and selectivity of NH3 over Mn–(O–C2)4 sites. [ABSTRACT FROM AUTHOR]

Despite lithium‐sulfur (Li‐S) batteries possessing ultrahigh energy density as great promising energy storage devices, the suppressing shuttle effect and improving sulfur redox reaction (SROR) are vital for their practical application. Developing high‐activity electrocatalysts for enhancing the SROR kinetics is a major challenge for the application of Li‐S batteries. Herein, single‐molecule iron phthalocyanine species are anchored on the N and P dual‐doped porous carbon nanosheets (Fe‐NPPC) via axial Fe‐N coordination to optimize the electronic structure of active centers. The Fe‐NPPC can promote the catalytic conversion of polysulfides by modulation of the electronic density in active moieties, endowing the Li‐S battery with a high reversible capacity of 1023 mAh g−1 at 1 C as well as an ultralow capacity decay of 0.035% per cycle over 1500 cycles. Even with a high sulfur loading of 7.1 mg cm−2, the Li‐S battery delivers a high areal capacity of 4.8 mAh cm−2 after 150 cycles at 0.2 C. With further increasing the sulfur loading to 9.2 mg cm−2, an excellent areal capacity of up to 9.3 mAh cm−2 is obtained at 0.1 C. [ABSTRACT FROM AUTHOR]

Simultaneously optimizing elementary steps, such as water dissociation, hydroxyl transferring, and hydrogen combination, is crucial yet challenging for achieving efficient hydrogen evolution reaction (HER) in alkaline media. Herein, Ru single atom‐doped WO2 nanoparticles with atomically dispersed Ru–W pair sites (Ru–W/WO2‐800) are developed using a crystalline lattice‐confined strategy, aiming to gain efficient alkaline HER. It is found that Ru–W/WO2‐800 exhibits remarkable HER activity, characterized by a low overpotential (11 mV at 10 mA cm−2), notable mass activity (5863 mA mg−1 Ru at 50 mV), and robust stability (500 h at 250 mA cm−2). The highly efficient activity of Ru–W/WO2‐800 is attributed to the synergistic effect of Ru–W sites through ensemble catalysis. Specifically, the W sites expedite rapid hydroxyl transferring and water dissociation, while the Ru sites accelerate the hydrogen combination process, synergistically facilitating the HER activity. This study opens a promising pathway for tailoring the coordination environment of atomic‐scale catalysts to achieve efficient electro‐catalysis. [ABSTRACT FROM AUTHOR]

Efficient electrocatalytic reactions require a coordinated active center that may provide a properly reaction intermediates adsorption in water splitting. Herein, a Ni active center coordination reconstruction method achieved by multidimensional modulation of phase transition, iodine coordination, and vacancy defects is designed and implemented. This coordination reconstruction results in the successful synthesis of Ni5P4−xIx/Ni2P nanocorals that show outstanding bifunctional catalytic activity due to deep optimization of the adsorption energy. The overpotentials of hydrogen evolution reaction and oxygen evolution reaction at 10 mA cm−2 are 46 and 163 mV, respectively. Only 1.46 V is required to drive alkaline overall water splitting. Novel coordination environment is investigated by electron paramagnetic resonance spectroscopy and extended X‐ray absorption fine structure spectroscopy. A 4D integrated material design strategy of "thermodynamic stability‐electronic properties‐charge transfer‐adsorption energy" for water‐splitting catalysts is proposed. This coordination reconstruction concept and material design method provide new perspectives for the research of novel catalysts. [ABSTRACT FROM AUTHOR]

Metal phthalocyanines (MPcs) have highly conjugated π electron systems and metal atoms acting as active centers, and so exhibit excellent electrocatalytic performance during the oxygen reduction reaction (ORR). However, these complexes also tend to undergo aggregation and exhibit poor electrical conductivity and minimal durability, all of which hinder their large‐scale industrial applications. In the present study, iron phthalocyanine (FePc) is applied to hollow carbon shells (HCSs) to generate an ORR catalyst containing single Fe atoms(HCS‐O‐FePc). The HCSs have numerous N/O‐based surface functional groups that promote the formation of Fe−O bonds with the FePc held in an axial coordination position. These axial Fe−O bonds disrupt the electron symmetry in the plane of the FePc molecules, which facilitate electron transfer. 1100HCS‐O‐FePc exhibits an onset potential of 0.98 V (vs RHE), a half‐wave potential of 0.91 V (vs RHE), an electron transfer number of 3.90, and durability better than that of a 20 % commercial Pt/C catalyst. Electrochemical impedance spectroscopy demonstrates that the ORR process over this material likely proceeds via a rapid 2+2 electron mechanism. This composite displays excellent oxygen reduction properties and is a promising alternative to Pt‐based ORR catalysts. [ABSTRACT FROM AUTHOR]

Accelerating slow water dissociation kinetics is key to boosting the hydrogen evolution reaction (HER) in alkaline media. We report the synthesis of atomically dispersed MoOx species anchored on Rh metallene using a one‐pot solvothermal method. The resulting structures expose the oxide‐metal interfaces to the maximum extent. This leads to a MoOx‐Rh catalyst with ultrahigh alkaline HER activity. We obtained a mass activity of 2.32 A mgRh−1 at an overpotential of 50 mV, which is 11.8 times higher than that of commercial Pt/C and surpasses the previously reported Rh‐based electrocatalysts. First‐principles calculations demonstrate that the interface between MoOx and Rh is the active center for alkaline HER. The MoOx sites preferentially adsorb and dissociate water molecules, and adjacent Rh sites adsorb the generated atomic hydrogen for efficient H2 evolution. Our findings illustrate the potential of atomic interface engineering strategies in electrocatalysis. [ABSTRACT FROM AUTHOR]

The integration of Fe dopant and interfacial FeOOH into Ni‐MOFs [Fe‐doped‐(Ni‐MOFs)/FeOOH] to construct Fe−O−Ni−O−Fe bonding is demonstrated and the origin of remarkable electrocatalytic performance of Ni‐MOFs is elucidated. X‐ray absorption/photoelectron spectroscopy and theoretical calculation results indicate that Fe‐O−Ni−O−Fe bonding can facilitate the distorted coordinated structure of the Ni site with a short nickel–oxygen bond and low coordination number, and can promote the redistribution of Ni/Fe charge density to efficiently regulate the adsorption behavior of key intermediates with a near‐optimal d‐band center. Here the Fe‐doped‐(Ni‐MOFs)/FeOOH with interfacial Fe−O−Ni−O−Fe bonding shows superior catalytic performance for OER with a low overpotential of 210 mV at 15 mA cm−2 and excellent stability with ≈3 % attenuation after a 120 h cycle test. This study provides a novel strategy to design high‐performance Ni/Fe‐based electrocatalysts for OER in alkaline media. [ABSTRACT FROM AUTHOR]

Non‐precious‐metal (NPM) catalysts often face the formidable challenge of a trade‐off between long‐term stability and high activity, which has not yet been widely addressed. Herein we propose a distinct molecule‐selective fence as a promising concept to solve this activity‐stability trade‐off. The fence encloses the catalyst and prevents species poisonous to the catalyst from reaching it, but allows catalytic reaction‐related species to diffuse freely. We constructed a CoS2 fence layer on the external surface of highly active cobalt‐doped MoS2, achieving a remarkable catalytic stability towards the alkaline hydrogen evolution reaction and improved activity. In situ spectroscopy uncovered the underlying molecular mechanism of the CoS2 fence for breaking the activity‐stability trade‐off of the MoS2 catalyst. This work offers valuable guidance for rationally designing efficient and stable NPM catalysts. [ABSTRACT FROM AUTHOR]

Uncovering the dynamics of active sites in the working conditions is crucial to realizing increased activity, enhanced stability and reduced cost of oxygen evolution reaction (OER) electrocatalysts in proton exchange membrane electrolytes. Herein, we identify at the atomic level potential-driven dynamic-coupling oxygen on atomically dispersed hetero-nitrogen-configured Ir sites (AD-HN-Ir) in the OER working conditions to successfully provide the atomically dispersed Ir electrocatalyst with ultrahigh electrochemical acidic OER activity. Using in-situ synchrotron radiation infrared and X-ray absorption spectroscopies, we directly observe that one oxygen atom is formed at the Ir active site with an O-hetero-Ir-N4 structure as a more electrophilic active centre in the experiment, which effectively promotes the generation of key *OOH intermediates under working potentials; this process is favourable for the dissociation of H2O over Ir active sites and resistance to over-oxidation and dissolution of the active sites. The optimal AD-HN-Ir electrocatalyst delivers a large mass activity of 2860 A gmetal−1 and a large turnover frequency of 5110 h−1 at a low overpotential of 216 mV (10 mA cm−2), 480–510 times larger than those of the commercial IrO2. More importantly, the AD-HN-Ir electrocatalyst shows no evident deactivation after continuous 100 h OER operation in an acidic medium. Uncovering the dynamics of active sites in the working conditions is important yet challenging. Here the authors identify dynamic-coupling oxygen on atomically dispersed iridium sites during oxygen evolution reaction using in situ techniques. [ABSTRACT FROM AUTHOR]

Exploring efficient noble‐metal‐free water‐splitting electrocatalysts from earth‐abundant elements is of great importance to realize wide applications in the generation of hydrogen fuel for clean energy. Here, a facile route is reported to synthesize ε‐Fe3N single‐phase nanoparticles by thermal ammonolysis of Fe precursors. The roles of nitrogen atoms in tailoring the hydrogen evolution reaction (HER) activities of ε‐Fe3N have been systematically investigated. HER activity is enhanced by reducing the effective coordination number of nitrogen atoms from 2.61 to 1.67, where the standard coordination number in ε‐Fe3N is 2. Density functional theory calculations reveal that the reduction of nitrogen content lowers the energy of Tafel process on the (1¯100)‐FeN‐exposed and (112¯0) N‐exposed surfaces. Both surfaces are thermodynamically favored for the HER. Furthermore, the active sites of Tafel process change from the kinetically less favored hollow sites of Fe atoms to the kinetically more favored top site of N atoms and the bridge site of Fe atoms on both (1¯100)‐FeN and (112¯0) N‐exposed surfaces. The findings propose a novel strategy to enhance HER activity by using nitrogen deficiency, which is of great importance for the development of highly active transition metal based electrocatalysts. [ABSTRACT FROM AUTHOR]

Herein, we report a comprehensive strategy to synthesize a full range of single‐atom metals on carbon matrix, including V, Mn, Fe, Co, Ni, Cu, Ge, Mo, Ru, Rh, Pd, Ag, In, Sn, W, Ir, Pt, Pb, and Bi. The extensive applications of various SACs are manifested via their ability to electro‐catalyze typical hydrogen evolution reactions (HER) and conversion reactions in novel room‐temperature sodium sulfur batteries (RT‐Na‐S). The enhanced performances for these electrochemical reactions arisen from the ability of different single active atoms on local structures to tune their electronic configuration. Significantly, the electrocatalytic behaviors of diverse SACs, assisted by density functional theory calculations, are systematically revealed by in situ synchrotron X‐ray diffraction and in situ transmission electronic microscopy, providing a strategic library for the general synthesis and extensive applications of SACs in energy conversion and storage. [ABSTRACT FROM AUTHOR]

For electrocatalysts for the hydrogen evolution reaction (HER), encapsulating transition metal phosphides (TMPs) into nitrogen‐doped carbon materials has been known as an effective strategy to elevate the activity and stability. Yet still, it remains unclear how the TMPs work synergistically with the N‐doped support, and which N configuration (pyridinic N, pyrrolic N, or graphitic N) contributes predominantly to the synergy. Here we present a HER electrocatalyst (denoted as MoP@NCHSs) comprising MoP nanoparticles encapsulated in N‐doped carbon hollow spheres, which displays excellent activity and stability for HER in alkaline media. Results of experimental investigations and theoretical calculations indicate that the synergy between MoP and the pyridinic N can most effectively promote the HER in alkaline media. [ABSTRACT FROM AUTHOR]

It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron–hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO2 support (Pt1/def‐TiO2). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO2 units to generate surface oxygen vacancies and form a Pt‐O‐Ti3+ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt‐O‐Ti3+ atomic interface effectively facilitates photogenerated electrons to transfer from Ti3+ defective sites to single Pt atoms, thereby enhancing the separation of electron–hole pairs. This unique structure makes Pt1/def‐TiO2 exhibit a record‐level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h−1, exceeding the Pt nanoparticle supported TiO2 catalyst by a factor of 591. [ABSTRACT FROM AUTHOR]

The key to improving water oxidation is to develop efficient and earth‐abundant catalysts for the oxygen evolution reaction (OER). Herein, a new amorphous cobalt iron borate supported on 3D carbon paper integrated electrode is reported as a precatalyst for the OER, which was synthesized by using a one‐pot hydrothermal method. An optimum OER activity was obtained at 25 % Fe doping by screening the compositions of the Co and Fe. The best synthesized catalyst needs an overpotential of 227 mV to deliver a current density of 10 mA cm−2 and also exhibits a long‐term durability of 24 h. Impressively, we find that CoFe oxyhydroxide was formed in situ in the OER process, which serves as the real catalytic active species for OER. Moreover, the direct conversion from CoFe borate to CoFe oxyhydroxide is reported for the first time in metal borate OER catalysts. The discovery in this work, that is, that metal borate as a precursor can efficiently catalyze the OER in alkaline media, significantly widens the family of OER catalysts. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) are currently one of the most active forefronts in heterogeneous catalysis. The vast majority of SACs are coordinated by highly electronegative heteroatoms like N and O, which often results in electron-deficient SACs and undesirable catalytic performance. Tuning the coordination environment of SACs by low-electronegativity species is essential, yet to date remains largely unexplored. Here, few-layer violet phosphorene (VP) was used as a giant phosphorus ligand to confine Ni single-atoms via a photoreduction approach. Combined experimental analysis and density-functional theory calculations confirmed that VP nanosheets covalently stabilized monovalent Ni (I) single-atoms in a Ni-P 4 atomic configuration. The active and durable Ni-P 4 moieties were shown to reduce the work function and band gap, optimize proton adsorption, and facilitate photoexcited charge separation, synergistically leading to a maximal hydrogen evolution rate of 377.8 μmol h−1g−1 which is an 11-fold increase than that of VP nanosheets. This work paves an avenue for the exploration of VP's enormous potential in solar-driven artificial photosynthesis as well as provides guidance to the rational design of P-coordinated SACs for diverse applications beyond water splitting. [Display omitted] • Immobilize single Ni atoms on few-layer VP via photoreduction deposition. • Identify atomically dispersed Ni-P4 moieties linked by Ni-P covalent-like bonds. • Achieve a hydrogen evolution rate which is 11-fold greater than that of VP nanosheets. • Reveal a synergy of local electronic structure, proton adsorption and charge separation on enhancing photoactivity. • Pave a path to the rational design of viable P-coordinated SACs. [ABSTRACT FROM AUTHOR]

The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo1N1C2). Importantly, the Mo1N1C2 catalyst displayed much more excellent activity compared with Mo2C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo1N1C2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts. [ABSTRACT FROM AUTHOR]

Pt cocatalyst play bifunctions in the photoreforming of polyethylene terephthalate plastic waste by improving the charge transfer kinetics and regulating the adsorption-desorption of oxidation intermediates, thereby achieving efficient photocatalytic H 2 evolution rate and producing valuable commodities in the photoreforming reactions. [Display omitted] Upcycle polyethylene terephthalate (PET) waste by photoreforming (PR) is a sustainable and green approach to tackle environmental problems but with challenges to obtain valuable oxidation products and high purity hydrogen simultaneously. Noble metal cocatalysts are essential to enhance the overall PR reaction efficacy. In this work, TiO 2 nanotubes (TiO 2 NTs) decorated with single Pt atoms (Pt 1 /TiO 2) or Pt nanoparticles (Pt NPs /TiO 2) are used in the photoreforming reaction (in one batch), and the oxidation products from ethylene glycol (EG, hydrolysed product of PET) in liquid phase and hydrogen are detected. With Pt 1 /TiO 2 , EG is oxidized to glyoxal, glyoxylate or lactate, and hydrogen evolution rate (r H 2) reaches 51.8 μmol⋅h−1⋅g cat −1, that is 30 times higher than that of TiO 2. For Pt NPs /TiO 2 (size of Pt NPs: 1.97 nm), hydrogen evolution reaches 219.1 μmol⋅h−1⋅g cat −1, but with the oxidation product of acetate only. DFT calculation demonstrates that for Pt NPs, the reaction path for hydrogen evolution is preferred thermodynamically, due to the formation of Schottky junction. On the oxidation of EG, theoretical and spectroscopic analysis suggest that bidentate adsorption of EG at the interface is facile on Pt 1 /TiO 2 , compared to that on Pt NPs /TiO 2 (two Pt sites), but oxidation products, adsorb less strongly, compared to Pt NPs /TiO 2 , that eventually regulates the distribution of oxidation products. The results thus demonstrate the bifunctions of Pt in the PR reaction, i.e., electron transfer mediator for hydrogen evolution and reactive sites for molecules adsorption. The oxidation reaction is dominated by the adsorption-desorption behavior of molecules but the reduction reaction is controlled by the electron transfer. In addition, acidification of pretreated PET alkaline solution achieves separation of pure terephthalic acid (PTA), which further improves the reaction efficiency possibly by offering high density of active sites and acidic environment. Our work thus demonstrates that to upcycle PET plastics, an optimized process can be reached by atomic design of photocatalysts and proper treatment on the plastic wastes. [ABSTRACT FROM AUTHOR]

• Decorate black phosphorene onto CdS nanospheres to create BP/CdS heterostructures by a grinding and sonication method. • Anchor Pt single-atoms on BP/CdS heterostructures via a photo-reduction deposition procedure. • Achieve a hydrogen evolution rate that is 96 times greater than that of CdS nanospheres, alongside an AQE of 46% at 420 nm. • Unravel interfacial electronic interactions, photoexcited charge-carrier dynamics and photocatalytic mechanism. • Pave a path to the rational design of viable co-catalysts at the nanoscale and atomic level. [Display omitted] Co-catalysts play a crucial role in semiconductor-based artificial photosynthesis and stabilizing co-catalysts on heterojunction photocatalysts is essential for achieving high photocatalytic efficiency. Herein, we report novel dual co-catalysts of black phosphorene (BP) and single Pt atoms on CdS nanospheres. BP/CdS heterostructures are prepared by grinding and sonication and then single Pt atoms are deposited onto BP/CdS through a photo-reduction procedure. In addition to being anchored on the surface step edges of CdS nanospheres, Pt single-atoms with positive charge are embedded on Cd vacancies and stabilized by Pt-S covalent bonds. Single Pt atoms are immobilized on the surface of BP as well. The as-prepared Pt-BP/CdS composites are evaluated toward visible-light-driven hydrogen generation. In a range of Pt and BP loading contents, 0.5 wt% Pt-5 wt% BP/CdS composites display the greatest photoactivity and outperform pristine CdS nanospheres by a factor of 96 in terms of hydrogen evolution rate, alongside a remarkable apparent quantum efficiency of 46% at 420 nm. In-depth analyses on interfacial electronic interactions and photoexcited charge-carrier dynamics demonstrate that both single Pt atoms and BP strongly interact with CdS and synergistically steer spatial charge separation, thereby boosting photocatalytic performance. This study may pave a path to the rational design of co-catalysts at the nanoscale and atomic level for solar-to-chemical energy conversion and beyond. [ABSTRACT FROM AUTHOR]

Electrochemical carbon dioxide reduction reaction (CO2RR) provides a promising pathway for both decreasing atmospheric CO2 concentration and producing valuable carbon‐based fuels. To explore efficient and cost‐effective catalysts for electrochemical CO2RR is of great importance, but remains challenging. Se‐doped carbon nanosheets (Se‐CNs) with a micro‐, meso‐, and macroporous structure are proposed for electrochemical CO2RR. Such an electrocatalyst combines the advantages of Se optimized active sites, hierarchical pores for facilitating reactant or ion penetration, transport and reaction, and large surface area for more accessible active sites. This Se‐CNs electrocatalyst exhibits over 11‐times enhanced partial current density of CO than the CNs without Se doping and high selectivity (90%) for CO2 electroreduction to CO at a low potential of −0.6 V versus the reversible hydrogen electrode (vs RHE). Density function theoretical calculations reveal that the Se introduction in CNs lowers the free energy barrier of CO2RR and inhibits hydrogen evolution reaction effectively, thus improving the selectivity for CO2 reduction to CO. This work presents a new member of the metal‐free electrocatalyst family, which is easily prepared, low cost, adjustable, and highly efficient for CO2RR. [ABSTRACT FROM AUTHOR]

The grand challenge in the development of atomically dispersed metallic catalysts is their low metal-atom loading density, uncontrollable localization and ambiguous interactions with supports, posing difficulty in maximizing their catalytic performance. Here, we achieve an interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS2 nanosheets (SA Co-D 1T MoS2). The phase of MoS2 transforming from 2H to D-1T, induced by strain from lattice mismatch and formation of Co-S covalent bond between Co and MoS2 during the assembly, is found to be essential to form the highly active single-atom array catalyst. SA Co-D 1T MoS2 achieves Pt-like activity toward HER and high long-term stability. Active-site blocking experiment together with density functional theory (DFT) calculations reveal that the superior catalytic behaviour is associated with an ensemble effect via the synergy of Co adatom and S of the D-1T MoS2 support by tuning hydrogen binding mode at the interface. While single-atom catalysis offers an efficient materials usage, the ambiguous interactions with supports poses a difficulty in understanding catalytic performances. Here, authors show an ensemble effect via synergy of Co adatoms and the S of MoS2 supports to boost hydrogen evolution activities. [ABSTRACT FROM AUTHOR]

Constructing well defined nanostructures is promising but still challenging for high‐efficiency catalysts for hydrogen evolution reaction (HER) and energy storage. Herein, utilizing the differences in surface energies between (111) facets of CoP and NiCoP, a novel CoP/NiCoP heterojunction is designed and synthesized with a nanotadpoles (NTs)‐like morphology via a solid‐state phase transformation strategy. By effective interface construction, the disorder in terms of electronic structure and coordination environment at the interface in CoP/NiCoP NTs is created, which leads to dramatically elevated HER performance within a wide pH range. Theoretical calculations prove that an optimized proton chemisorption and H2O dissociation are achieved by an optimized phosphide polymorph at the interface, accelerating the HER reaction. The CoP/NiCoP NTs are also proved to be excellent candidates for use in supercapacitors (SCs) with a high specific capacitance (1106.2 F g−1 at 1 A g−1) and good cycling stability (nearly 100% initial capacity retention after 1000 cycles). An asymmetric supercapacitor shows a high energy density (145 F g−1 at 1 A g−1) and good cycling stability (capacitance retention is 95% after 3200 cycles). This work provides new insights into the catalyst design for electrocatalytic and energy storage applications. [ABSTRACT FROM AUTHOR]

Urea is of great importance for the survival and development of mankind because of its advantages in effectively increasing crop yields. A novel carbon-supported indium-doped bismuth nanoparticles (Bi: 10 %In/C NPs) was prepared for the synthesis of urea via the co-activated reduction of nitrate and CO 2 with an average Faraday efficiency (FE) of 20.31 % and urea yield (R urea) of 606.38 μg mg−1 h−1. Interestingly, the In doped here not only serves as the active site, but also acts as an activator to stimulate the activity of Bi through electronic interaction, thus making Bi also the active site for the electrocatalytic C-N coupling reaction. Simultaneously, the key intermediates of the reaction are revealed to be *NH 2 and *CO. This work provides further insight into the role of indium in the electrocatalytic C-N coupling for the synthesis of urea, which gives a direction for thinking about the design and construction of subsequent highly efficient electrocatalysts. A novel catalyst based on carbon-supported In-doped Bi nanoparticles (Bi:10 % In/C NPs) was prepared for the co-activated reduction of nitrate and CO 2 for the synthesis of urea with average FE and urea yield of 20.31 % and 606.38 μg mg−1 h−1 at − 0.45 V vs. RHE. The key intermediates of the reaction are revealed to be *NH 2 and *CO. Interestingly, experimental results show that the doped In acts not only as the active site but also as an "activator", stimulating the activity of Bi through electronic interactions, thus making Bi also the active site for electrocatalytic C-N coupling reactions. [Display omitted] ● A bismuth-based catalyst well suited for the electrochemical synthesis of urea (FE: 20.31 %, R urea : 606.38 μg mg−1 h−1) was prepared by a simple room temperature reduction method based on the property of bismuth to inhibit competitive hydrogen evolution reactions. ● A strategy for the preparation of electrocatalysts for highly efficient urea synthesis using direct activation of bismuth by indium is proposed for the first time. ● Theindium in the prepared Bi:In/C not only directly participates in the synthesis of urea as the active site, but also acts as an activator to activate the inert bismuth, so that bismuth also becomes the active site of the C-N coupling reaction, thus greatly improving the efficiency and stability for the synthesis of urea. [ABSTRACT FROM AUTHOR]

• Mo 2 C/CFP-Act is prepared via continuous cathode polarization technique. • Mo 2 C/CFP-Act is an excellent electrocatalyst for the hydrogen evolution reaction. • Mechanism study unveils the Pt single atom intrinsic role in Mo 2 C/CFP catalysts. Dispersing catalytically active metals as single atoms on supports offer an efficient pathway to minimize amount of precious metals. Although platinum (Pt) is highly active for HER, it is highly desirable to find ways to improve the HER performance and also keeping them stable during catalytic reactions while minimizing the Pt loading. Herein, we report a cathode polarization technique to disperse isolated single Pt atoms on β-Mo 2 C as a catalyst for HER. The isolated Pt atoms partially occupy Mo sites in Mo 2 C lattice by forming Pt-Mo shells, which maximize the utilization ratio of platinum noble metals. The single atoms catalyst Mo 2 C/CFP-Act even exhibited 1.9 and 1.1 times higher current density (@ potential of 0.4 V vs. RHE) than that of Pt NPs catalysts (Mo 2 C/CFP-Pt) after mass normalization in both acidic and alkali solution. Furthermore, DFT calculations demonstrate that Mo 2 C/CFP-Act exhibits favorable ΔG H* for the adsorption and desorption of hydrogen. The high HER activity of the Mo 2 C/CFP-Act catalyst is related to the Mo-Pt center located in Mo 2 C matrix, where the electronic structure of the Mo-Pt centers more efficient in donating electron to the σ* antiorbital of the H 3 O+ molecule. This study sheds new light on the HER catalysis mechanism of isolated metal atoms based on fundamental understanding in molecular governing factors. [ABSTRACT FROM AUTHOR]

Given the efficiency, stability and sustainability, the carbon-based materials have become one of promising bifunctional electrocatalysts to the electrochemical water splitting, involving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, there are still many challenges about the design and mechanism study of the carbon-based electrocatalysts. In this paper, we reported B, N co-doping carbon nanosheets which were synthesized via cationic intercalation stripping guar gum carbon aerogels pre-crosslinked by borate, B(OH) 4 -. This facile strategy not only realizes the structure tailoring, but also concurrently improves the doping efficiency and the stability of the hetero atoms. Specifically, the cost-efficient carbon-based bifunctional catalyst (B5/GCS) shows an outstanding HER and OER performance displaying a remarkable activity both in acidic and alkaline media, low onset potentials for both HER (39.12 mV) and OER (1.38 V) in the same electrolyte (0.5 M H 2 SO 4). Notably, when employed as the bifunctional electrocatalysts with a two-electrode electrolyzer for water splitting, the B5/GCS generated a cell voltage of 1.45 V to attain 10 mA cm−2 in 0.5 M H 2 SO 4. Furthermore, a series of experiments combining density functional theory calculations revealed that the observed superb water splitting activity could be attributed to a synergistic effect of N, B co-doping and the formation of fragmented nanosheets with topological defects, which collaboratively promotes the proton adsorption and catalytic kinetics. A advanced carbon-based bifunctional catalyst are designed and fabricated by a facile two-step strategy - borate chemical crosslinking guar gum gel and subsequent cationic intercalation stripping, as water splitting catalyst, the optimal B5/GCS exhibits extraordinary HER and OER performance – on par with the benchmark noble metal catalyst. Image 1 [ABSTRACT FROM AUTHOR]

This paper describes the effects of defect distribution on energy band structure and the subsequent photocatalytic activity over TiO 2 with exposed {001} facets as the model catalyst. Our results show that only surface oxygen vacancies (V o ’s) and Ti 3+ centers in TiO 2 can be induced by hydrogenation treatment, whereas the generation of bulk V o ’s and Ti 3+ species depends on the thermal treatment in nitrogen. Both the surface and bulk defects in TiO 2 can promote the separation of electron-hole pairs, enhance the light absorption, and increase the donor density. The presence of surface and bulk defects in TiO 2 can not change the valence band maximum, but determine the conduction band minimum. Surface defects in TiO 2 induce a tail of conduction band located above the H + /H 2 redox potential, which benefits the photocatalytic performance. However, bulk defects in TiO 2 generate a band tail below the H + /H 2 potential, which inhibits hydrogen production. Thus, the change of band gap structure by defects is the major factor to determine the photocatalytic activity of TiO 2 for hydrogen evolution. It is a new insight into the rational design and controllable synthesis of defect-engineered materials for various catalytic processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensional ordered macroporous frameworks with NiN 4 sites were obtained. • 3DOM Ni N C was highly efficiency for ORR and OER performances in neutral condition. • The neutral zinc-air batteries exhibited outstanding long term stability of 580 cycles at 1.0 mA cm−2. • The failure mechanism of air electrode in neutral condition was revealed. Neutral zinc-air batteries prevent the carbon based catalysts from being oxidized during cycling, which show excellent potential for long-term energy storage. Three-dimensional ordered macroporous nitrogen doped carbon frameworks with NiN 4 (3DOM Ni N C) were constructed by in situ reaction of Ni nanoparticles and dicyandiamide. The 3DOM Ni N C bifunctional catalysts exhibit comparable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) efficiency and stablity. The 3D interconnected structure of 3DOM Ni N C provides sufficient channel for mass transfer, resulting in high power density (35 mW cm−2) and long cycle life (580 cycles) of neutral zinc-air batteries. Meanwhile the failure mechanism in neutral electrolyte was discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru clusters are immobilized on hierachical Ni 3 N arrays. • The interfacial Ru atoms enable long-range Ni atoms as active sites via electron delocalization. • The H 2 O and H* adsorption energies are strengthened and weakened, respectively. • An outperforming Pt/C benchmark activity is achieved at ≥ 125 mA cm−2. Hydrogen (H 2) production from alkaline water electrocatalysis is economically appealing yet significantly hindered by the sluggish H 2 O adsorption and H* binding kinetics on active sites during hydrogen evolution reaction (HER). Herein, we interfacially immobilize Ru clusters on the hierarchical nickel nitride (Ru-Ni 3 N) nanosheet arrays via the filling of Ru3+ species into the metal vacancies of nickel hydroxide precursors and the subsequent controllable nitridation. The optimized Ru-Ni 3 N shows the outstanding HER performance, affording a 30-fold rise in the intrinsic activity of Ni sites, a outperforming-Pt/C overpotential at ≥ 125 mA cm−2 while remaining a robust stability. We further establish by a combined study of density functional theory (DFT) calculations with experimental analyses that long-range Ni sites around Ru sites act as active sites via the electron delocalization, remarkably weakening the H 2 O adsorption and H* binding barriers for enhancing the alkaline HER kinetics. Moreover, it also demonstrates an excellent pH-universal HER and overall water splitting performance. [ABSTRACT FROM AUTHOR]

Development of efficient electrocatalysts requires construction of catalytic surfaces with moderate H adsorption energy. Here, we address this challenge by Br-induced formation of P-poor defective nickel phosphide and show that the H adsorption energy can be optimized by regulating the vacancy concentration. We show that when such defective Ni 12 P 5−x Br x nanoparticles are distributed on the surface of Ni 2 P nanosheets (Ni 12 P 5−x Br x /Ni 2 P NS), excellent catalytic activity for water splitting is obtained in alkaline media. Density functional theory computations revealed that Br doping induce the formation of a P-poor nickel phosphide with vacancies, leading to an optimal H adsorption strength with a volcano-type relationship. This is the best reported for a non-precious metal phosphide at present: the overpotential for HER is 18 mV at 10 mA cm−2 and 155 mV for OER. This leads to an exceptionally low cell voltage requirement of only 1.44 V to drive overall water splitting in an alkaline electrolyzer. [Display omitted] • Br-induced nickel phosphide formation energy change achieves P-poor defective phase configuration. • Multi-level regulation of vacancy content, morphology and catalytic performance by temperature is achieved. • DFT calculations show that Ni 12 P 5−x Br x shows a volcano-type relationship related to vacancy content. [ABSTRACT FROM AUTHOR]

Efficiency of the electrocatalysts for hydrogen evolution reaction (HER) strongly depends on their extrinsic physical properties and intrinsic electronic structures. Among various modulation strategies, nanoalloying is an efficient route to regulate the intrinsic activities of HER intermediates. Herein, we develop a facile and universal one-step pyrolyzed method to fabricate bimetallic Ru-based nanoalloy catalysts encapsulated by B/N co-doped graphitic nanotubes (RuM@BCN, M=Ir, Pt, Ag, Co, and Fe) for high-performance alkaline HER. BCN nanotube substrates provide sufficient open channels, porous structures and strong anchoring effect to achieve fast kinetics and high stability. The bimetallic nanoalloying strategy greatly promotes the water dissociation and hydrogen adsorption ability of the electrocatalysts via modulation on their intrinsic electronic structures. Therefore, the as-made RuM@BCN demonstrates varied HER behaviors by alloying metals, in which RuIr@BCN exhibits the highest alkaline HER activity with an overpotential of 23.6 mV at the current density of 10 mA cm−2, outperforming commercial Pt/C. [Display omitted] • A general and facile strategy is developed to fabricate bimetallic RuM@BCN nanotubes. • Alloying Ru and Ir atoms induces electronic structure changes and promotes alkaline HER. • BCN nanotubes show great potentials to embed various Ru-based nanoalloy catalysts. • RuIr@BCN demonstrates an overpotential of 23.6 mV at 10 mA cm− 2 for alkaline HER. [ABSTRACT FROM AUTHOR]

Tandem Catalysis on dual active sites A highly-efficient electrocatalyst containing dual active sites of Fe-NiOOH and NiC 4 single atoms was synthesized, and a tandem catalysis mechanism of OER on dual active sites was proposed to reveal the high-activity origin of the catalysts. This work provides a new concept of tandem catalysis to develop the electrocatalysts with many elementary steps, like OER and ORR. [Display omitted] • A highly-efficient electrocatalyst containing dual active sites of Fe-NiOOH and NiC 4 single atoms was synthesized. • The dual active site electrocatalyst shows obviously better OER performance than the corresponding single active site one. • A tandem catalysis mechanism was proposed to reveal the synergistic catalysis of two active centers. • This work provides a new concept of tandem catalysis to develop the electrocatalysts with many elementary steps, like OER and ORR The high voltage in oxygen evolution reaction (OER) often causes structural change in electrocatalysts and forms multiple active sites. Therefore, exploring the synergy of various active sites is extremely significant to develop catalysts for OER with multiple elementary steps. Herein, we adopt the physically adsorbed metal ions method to successfully synthesize a highly-efficient electrocatalyst containing the dual active sites of Fe-NiOOH and NiC 4 single atoms (marked as Ni SAs/Fe-NiOOH). The Ni SAs/Fe-NiOOH displays outstanding OER performance with an overpotential of 269 mV to deliver current density of 10 mA/cm2 that shows 55 mV superior to commercial IrO 2 /CB at the same condition. Experiments and density functional theory calculations indicate that the excellent OER activity of Ni SAs/Fe-NiOOH catalyst is attributed to the synergy of dual active sites of NiC 4 SAs and Fe-NiOOH. A tandem catalysis mechanism is also proposed to reveal the synergism of two active centers, which makes the potential-determining step more facile and accordingly decreases the OER overpotential. This work offers a new concept of tandem catalysis to develop the electrocatalysts with many elemental steps, like OER and oxygen reduction reaction catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • We report a cheaper yet higher efficient HER electrocatalyst than Pt. • The Ru@2D-NC is synthesized though a simple organic/aqueous interfacial strategy. • It exhibits low η @10 of 31 and 29 mV in alkaline and acidic media respectively. • Optimized ΔG(H*) and ΔG B (H 2 O) are obtained via interatomic charge redistribution. • The strong Ru-support interaction endows the catalyst with excellent durability. The development of efficient and durable electrocatalysts for hydrogen evolution reaction (HER) is crucial for sustainable electrochemical water splitting and its practical application. However, the inappropriate binding with H* and sluggish reaction kinetics limit their overall HER performance, especially in alkaline electrolyte. Herein, we report a robust and high active HER electrocatalyst with optimized metal-H* interaction and low water dissociation energy barrier through interatomic d-p orbital hybridization. The Ru nanoparticles with mean size down to 1.7 nm are anchored on two-dimension nitrogen-doped carbon nanocone arrays via a facile aqueous-organic interfacial method. This unique architecture induces strong interaction between Ru and the carbon support. Electrons are transferred from Ru to the N-doped carbon, causing a shift of charge distribution and modified surface properties of Ru. Furthermore, the newly emerged Ru-N bonds endow the catalyst with high structure robustness. As a result, the catalyst exhibits superior HER performances in both alkaline and acidic electrolytes, with low overpotentials (31 and 29 mV at 10 mA cm−2 respectively), high H 2 turn over frequency (2.20 s−1 at the overpotential of 25 mV) and excellent durability (10,000 cycles). The density functional theory calculations reveal that the boosted HER activity can be attributed to the downshift of the d-band center of Ru, which lowers the |ΔG(H*)| and accelerates the H-OH cleavage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-supported electrocatalysts are prepared via solid-state diffusion. • Effective mass-transfer between carbon-layers and Ni endowing electrocatalyst with ultrahigh activity. • The district confinement of CNTs and heteroatomic doping collaboratively promotes kinetics. To satisfy the practical requirements of electrochemical water splitting, developing a flexible, effective and sustainable approach for scalable production of bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a tremendous issue to be rationally addressed. Herein, a solid-state diffusion strategy with Ni foam and N-doped carbon layers is applied to prepare multi-interfacial, self-supported and N-doped carbon nanotube (NCNT) encapsulated Ni nanoparticles (NPs) array bifunctional electrocatalyst (NCNT-NP@NF). Prominently, this NCNT-NP@NF is scalable to meet the application requirements and can be used as a binder-free electrode for direct the water splitting. The optimal sample demonstrate outstanding HER/OER performance in 1.0 M KOH, with low overpotential (η 10) at 10 mA cm−2 during HER (96.1 mV) and OER (240 mV) process, which is extremely superior to the most reported metal-based electrocatalysts and even better than commercial IrO 2 (400 mV at 10 mA cm−2 for OER). Strikingly, when these bifunctional electrocatalysts are employed in a dual-electrode electrolyzer for water splitting, the NCNT-NP@NF only needs cell voltage of 1.54 V to drive overall water splitting in 1.0 M KOH, and displays excellent long-term stability (150 h for water splitting). Moreover, experiments combined with density functional theory (DFT) calculations clarify that the remarkable electrochemical activity and stability are mainly attribute to the synergistic effect of the uniform distribution of Ni NPs, heteroatomic doping, as well as district confinement effect of NCNT leading to enhanced electronic multi-interfacial transmission, all these factors co-accelerate electrocatalytic kinetics. Accordingly, this solid-state diffusion method possesses a favorable potential to construct a multi-interfacial and self-supported electrocatalysts in the fields of sustainable supply of clean energies. [ABSTRACT FROM AUTHOR]

A novel structure of Fe-doped NiO coupled Ni cluster hollow nanotube arrays (Fe-NiO-Ni CHNAs) composed of defect-rich NiO phase and Ni clusters anchored on outside of nanotubes is presented. The d-band downshifted by Fe-doping, coupled of Ni clusters and defect-rich nature greatly improve electrocatalytic performances of Fe-NiO-Ni CHNAs toward oxygen evolution reaction. • A multi-level structure of Fe-doped NiO coupled Ni cluster hollow nanotube arrays (Fe-NiO-Ni CHNAs) was synthesized as a catalyst for OER. • Fe-NiO-Ni CHNAs exhibits overpotential of 245 mV at 10 mA cm−2 and outstanding durability that surpasses most of transition metal oxides. • The improved OER activity is mainly because Fe doping downshifts the d-band of metal sites. • Fe-NiO-Ni CHNAs obeyed the adsorbate evolution mechanism with a nonconcerted proton-electron transfer pathway. Herein we present a novel multi-level structure of Fe-doped NiO coupled Ni cluster hollow nanotube arrays (Fe-NiO-Ni CHNAs) grown on carbon fiber cloth as an efficient catalyst for oxygen evolution reaction. In this multi-level structure, rocksalt-type Fe-doped NiO phase hybrids with Ni clusters coupled into the nanospheres anchored to the outside of nanotube, forming a unique 3D corn-like structure. This novel multi-level structure represents a large specific area for catalytic reaction. X-ray absorption fine structure indicates that the defect-rich Fe-doped NiO phase has abundant coordinative unsaturated sites as active sites, and Fe doping downshifts the d-band of metal sites, which is the main contribution to the improved oxygen evolution reaction catalytic activity. The OER of Fe-NiO-Ni CHNAs obeys the adsorbate evolution mechanism with the nonconcerted proton-electron transfer pathway as a rate-determining step. Thus Fe-doped NiO CHNAs exhibits excellent OER performance and outstanding durability that surpasses most of transition metal oxides. [ABSTRACT FROM AUTHOR]

• Inherent chemical cross-linking gives M-SA@NCA an ultra-high single-atom loading. • More active sites and excellent stability in overwater splitting process. • Pivotal synergy optimize electric structure via different configuration. Rationally designing single-atom catalysts (SACs) is a potential strategy to reach efficient energy conversion as they combine the merits of both maximizing atomic utilization and minimizing the cost of the heterogeneous catalysts. However, when increasing the loading capacity of single-atoms, how to effectively prevent the aggregation of metal single atoms to achieve higher atom utilization efficiency is an urgent issue. Herein, we develop an in-situ pre-crosslinking method to prepare a series of metal single-atoms anchored on nitrogen-doped carbon aerogel (M-SA@NCA, M = Co, Ni, Mo) as high-efficiency bifunctional catalysts for hydrogen/oxygen evolution reactions (HER/OER). Thanks to the intrinsic chemical crosslinking ability between the metal ions and the substrate functional groups, these metal single-atoms can be effectively and stably anchored in the three-dimensional network as crosslinked point of the substrate, thus endowing M-SA@NCA with ultrahigh single-atom loading (Co, ~27.30 wt%; Ni, ~18.35 wt%; Mo, ~18.16 wt%), and therefore display more active sites, and excellent stability (up to 100 h for water-splitting in 1.0 M KOH). Furthermore, the systematic X-ray absorption fine structure (XAFS), in-situ attenuated total internal reflection (in-situ ATR spectra) and density functional theory (DFT) calculation are used to acquire deep insight on the bonding modes between metal single-atoms and substrates, and the influence of different configuration on the catalytic performance. The combined results reveal that Co atoms facilitate the formation of pyrr-N, and the optimal configuration is CoN 4 in HER process with smallest onset potential of 12.5 mV, closing to the Pt/C (20 wt%); while the best OER catalyst is Ni-SA@NCA with NiC 2 N 2 -o-5 moieties, outperforming the benchmarked IrO 2. This work provides a solution for investigating the interaction between single-atom-substrate configuration and catalytic performance, and represents a critical step towards the rational design and synthesis of SACs with extremely high single-atom loading, maximum atomic utilization efficiency and thus superior catalytic activity. [ABSTRACT FROM AUTHOR]

Asymmetric Embedding Benzene Ring in graphite carbon nitride changes local charge distribution and electron transfer kinetics, and promote the photocatalytic water splitting to produce hydrogen at a higher rate. • The A-GCN is successfully prepared using dicyandiamide and terephthalonitrile. • Embedding benzene regulate the localized electronic structure. • Theoretical results predicts the localized asymmetry promotes the charge transfer. • For hydrogen production, the A-GCN-1.0 displays 10.8 times as good as pristine GCN. Preventing the high carrier recombination rate of graphitized C 3 N 4 (GCN) is an urgent problem to be solved for its application as a photocatalyst for hydrogen production. Here, we first rationally embed the benzene ring in GCN to modify the local symmetry without changing its long-order structure. Theoretical calculation predicts that this design can change the electronic structure and promote the effective charge transfer in GCN. The benzene ring embedded GCN is successfully prepared by copolymerization using dicyandiamide and terephthalonitrile as precursors. Photoluminescence (PL) and time-resolved transient PL (TRPL) spectra confirm that the electron transfer efficiency of the benzene ring embed GCN is greatly improved. This nanomaterial displays 10.8 times higher photocatalytic hydrogen production rate than that of pristine GCN with the apparent quantum yield of 11.3% at 400 nm and 9% at 420 nm. This work provides a novel strategy for designing high-efficiency two-dimensional (2D) photocatalytic materials for water splitting. [ABSTRACT FROM AUTHOR]