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Realizing efficient electrocatalysts is a stepping stone toward achieving high‐performance alkaline water/seawater electrolysis, but remains a crucial challenge. Herein, heterogeneous Mo2N/Ni3Mo3N electrocatalysts on nickel foam (denoted MN‐NMN/NF) that is stable and active for the hydrogen evolution reaction (HER) in both alkaline water/seawater are demonstrated. The optimized MN‐NMN09/NF achieves an ultralow HER overpotential of 11 mV@10 mA cm−2 in 1.0 m KOH electrolyte, which is not only superior to the benchmark Pt/C catalysts but also the best reported ever among NiMo‐based electrocatalysts in an alkaline environment. Successively, the optimized MN‐NMN09/NF electrocatalyst can drive HER current densities of 10 and 500 mA cm−2 using low overpotentials of 9.37 and 123 mV in 1.0 m KOH seawater electrolyte, which remains durable after 120 h long‐term electrolysis at a constant current density of 500 mA cm−2. In situ Raman analysis reveals that the enhanced performance is attributed to the accelerated H2O adsorption and OH dissociation processes on the MN‐NMN surfaces. Theoretical analysis further confirms that rapid H2O adsorption‐dissociation kinetics and H adsorption‐conversion kinetics on the Ni3Mo3N/NiOOH and Ni3Mo3N/MoOx surfaces result in boosted HER capability. This work depicts a significant potential for designing stable and efficient hydrogen production electrocatalysts for both alkaline water and seawater electrolysis. [ABSTRACT FROM AUTHOR]

The oxygen evolution reactions in acid play an important role in multiple energy storage devices. The practical promising Ru-Ir based catalysts need both the stable high oxidation state of the Ru centers and the high stability of these Ru species. Here, we report stable and oxidative charged Ru in two-dimensional ruthenium-iridium oxide enhances the activity. The Ru0.5Ir0.5O2 catalyst shows high activity in acid with a low overpotential of 151 mV at 10 mA cm−2, a high turnover frequency of 6.84 s−1 at 1.44 V versus reversible hydrogen electrode and good stability (618.3 h operation). Ru0.5Ir0.5O2 catalysts can form more Ru active sites with high oxidation states at lower applied voltages after Ir incorporation, which is confirmed by the pulse voltage induced current method. Also, The X-ray absorption spectroscopy data shows that the Ru-O-Ir local structure in two-dimensional Ru0.5Ir0.5O2 solid solution improved the stability of these Ru centers. Stabilizing high oxidation state of Ru centers is important to achieve stable performance for acidic oxygen evolution reaction. Here the authors report two-dimensional ruthenium-iridium oxide for enhanced stability and activity for acidic water oxidation in proton exchange membrane electrolyzer. [ABSTRACT FROM AUTHOR]

Metastable noble metal nanocrystals may exhibit distinctive catalytic properties to address the sluggish kinetics of many important processes, including the hydrogen evolution reaction under alkaline conditions for water-electrolysis hydrogen production. However, the exploration of metastable noble metal nanocrystals is still in its infancy and suffers from a lack of sufficient synthesis and electronic engineering strategies to fully stimulate their potential in catalysis. In this paper, we report a synthesis of metastable hexagonal Pt nanostructures by coherent growth on 3d transition metal nanocrystals such as Ni without involving galvanic replacement reaction, which expands the frontier of the phase-replication synthesis. Unlike noble metal substrates, the 3d transition metal substrate owns more crystal phases and lower cost and endows the hexagonal Pt skin with substantial compressive strains and programmable charge density, making the electronic properties particularly preferred for the alkaline hydrogen evolution reaction. The energy barriers are greatly reduced, pushing the activity to 133 mA cmgeo–2 and 17.4 mA μgPt–1 at –70 mV with 1.5 µg of Pt in 1 M KOH. Our strategy paves the way for metastable noble metal catalysts with tailored electronic properties for highly efficient and cost-effective energy conversion. Synthesis and modulation of metastable noble metal nanocrystal catalysts is interesting yet challenging. Here the authors report synthesis of metastable hexagonal Pt skins on Ni nanocrystals with modulated electronic structures and enhanced hydrogen evolution activities. [ABSTRACT FROM AUTHOR]

The design and preparation of efficient electrocatalysis to promote electrochemical water-splitting are vital for the hydrogen economy. Catalytic kinetics can be significantly enhanced by adjusting the structure and composition of non-noble metal electrocatalysts. Herein, we report efficient and low-cost FeNi alloys/oxyhydroxide nanostructure composites via one-step galvanostatic electrodeposition on cleaned SSM (stainless steel mesh). In a 1.0 M KOH solution, the as-prepared FeNi-(1 : 1) Ox(OH)y can efficiently convert water to H2 and O2 with overpotentials of 325 and 347 mV, respectively, to achieve a current density of 100 mA cm−2. The construction of an alkaline electrolytic cell by employing FeNi-(1 : 1) Ox(OH)y as anode and cathode achieved an overall cell voltage of 1.897 V to attain 100 mA cm−2 for 1.0 M KOH. Theoretical and experimental analyses indicate an FeNi alloys/oxyhydroxide heterostructure can be used to modulate the microenvironment on the surface to obtain the optimal microenvironment for HER and OER. Our strategy of heterointerface engineering to construct microenvironment-enhancing catalytic kinetics may create a promising pathway to develop the overall water-splitting performance of the binary metal alloy. [ABSTRACT FROM AUTHOR]

Based on that hydrogen energy is widely used in fuel cells, the design and research of new catalysts for both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) are becoming increasingly important. A new catalyst for both hydrogen evolution and oxidation, based on a zinc complex, [Zn‐ATSE]2, is designed and provided by the reaction of Zn (CH3CO2)2 with diacetyl‐2‐(4‐N‐ethyl‐3‐thiosemicarbazone)‐3‐(4‐N‐amino‐3‐thiosemicarbazone) (H2ATSE) in our group. Electrochemical investigations show that [Zn‐ATSE]2 can electro‐catalyze hydrogen evolution from acetic acid with a turnover frequency (TOF) of 64 mol H2 mol catalyst−1 h−1 under an overpotential of 914.6 mV. Moreover, [Zn‐ATSE]2 also can electro‐catalyze hydrogen oxidation with a TOF of 13.52 s−1. The results can be attributed to the hydrazine group of [Zn‐ATSE]2 that can form a ligand‐based radical species. Possible electrocatalytic cycles for H2 production and oxidation by [Zn‐ATSE]2 are afforded. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation. [ABSTRACT FROM AUTHOR]

In this work, two complexes with bipyridine ligand, [Co (bpy)2(SCN)2] 1 and [Ni (bpy)2(SCN)2] 2 have been prepared and well determined by single crystal X‐crystallography, power X‐ray diffraction (XRD), IR spectra, and so forth. Both exhibit good catalytic activity for electrochemical‐ and photochemical driven‐hydrogen evolution. Complexes 1 and 2 can electro‐catalyze H2 evolution from a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 699.6 and 1469 mol H2/mol catalyst/h at an overpotential (OP) of 837.6 mV, respectively. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid as a sacrificial electron donor, complexes 1 and 2 also can photo‐catalyze H2 evolution from water. Under an optimal condition, the turnover numbers (TONs) reach 10,600 (complex 1) and 15,180 (complex 2) mol of H2 per mol of catalyst during 48‐h irradiation, respectively. The average apparent quantum yields (AQYs) of complex 1 and complex 2 are 15.07% and 22.7%, respectively. Electrochemical and photochemical investigations show that the nickel complex has a higher activity for hydrogen evolution than that of the cobalt complex. These results can provide a new insight into design and manufacture of new H2‐production catalyst. Highlights: Reactions of bipyridine (bpy), KSCN and MIICl2 (M = Co and Ni) afford [Co (bpy)2(SCN)2] 1 and [Ni (bpy)2(SCN)2] 2, respectively.Under an overpotential (OP) of 837.6 mV, 1 and 2 provide 699.6 and 1469 mol H2/mol catalyst/h from buffer solution, respectively.Complexes 1 and 2 also can photo‐catalyze H2 evolution with a turnover number (TON) of 10,544 and 15,160, respectively, respectively.Complex 2 exhibits a much higher catalytic efficiency for hydrogen production than 1. The result is attributed to that nickel exhibits higher electronegativity than cobalt, amenable to binding to H+ and hydrogen production, and a smaller bandgap in [Ni (bpy)2(SCN)2] (1.104 eV) than in [Co (bpy)2(SCN)2] (1.7443 eV). [ABSTRACT FROM AUTHOR]

The edge sites of MoS2 are catalytically active for hydrogen evolution reactions (HER). However, pristine edge sites usually contain only intrinsic atoms or defects, limiting the tuning of on‐site hydrogen species adsorption and desorption, the critical steps for HER. In addition, the number of atoms on pristine edges is small compared to that of electrochemically inert atoms in bulk. Thus, it is desirable to develop a scalable technique of creating a large number of highly HER‐active edge sites. Here, a plasma etching strategy is developed for creating MoS2 edge electrodes with a controllable number of active sites that enable the quantitative characterization of their HER activity using a local probe method. Fluorine atoms with large electronegativity are doped on the MoS2 edge sites that lead to a fivefold activity enhancement compared to that from pristine edges and is attributed to the more moderate binding energy for hydrogen species. The scalability of such a method is further demonstrated by activating MoS2 catalyst in macroscopic quantities with enhanced HER performance and stability. The work provides two‐dimensional materials as a platform for understanding the doping effect on the edge sites at atomic‐level, and offers a novel route for the design of efficient catalysts. [ABSTRACT FROM AUTHOR]

Based on that hydrogen energy is widely used in fuel cells, we focus our interests on the design and research of new complexes that catalyze the reaction in both directions, such as hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs). A highly efficient catalyst for both hydrogen evolution and oxidation, based on a nickel(II) complex, [Ni-en-P 2 ](ClO 4) 2 , has been designed and provided by the reaction of Ni(ClO 4) 2 with N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P 2) in our group. Its structure has been determined by X-ray diffraction. [Ni-en-P 2 ](ClO 4) 2 can electro-catalyze hydrogen evolution both from acetic acid and a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 204 and 1327 mol of hydrogen per mole of catalyst per hour (H 2 /mol catalyst/h) under an overpotential (OP) of 914.6 mV and 836.6 mV, respectively. [Ni-en-P 2 ](ClO 4) 2 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s−1 under an OP of 330 mV. The results can be attributed to that [NiII-en-P 2 ](ClO 4) 2 has three good reversible redox waves at 1.01 (NiIII/II), −0.79 (NiII/I) and −1.38 V (NiI/0) versus Fc+/0, respectively. We hope these findings can afford a new method for the design of electrocatalysts for both H 2 evolution and H 2 oxidation. [Display omitted] • Reaction of en-P 2 with Ni(ClO 4) 2 affords a nickel complex, [Ni-en-P 2 ](ClO 4) 2 1. • 1 catalyzes H 2 evolution from buffer (pH 7) with a TOF of 1327H 2 /mol catalyst/h at OP of 836.6 mV. • 1 also can catalyze H 2 oxidation with a TOF of 111.7 s−1 at an OP of 330 mV. [ABSTRACT FROM AUTHOR]

Reactions of bis(methylthioether)pyridine (btep) with CuX2 (X = Br and Cl) form two new complexes, [Cu(btep)Br2] and [Cu(btep)Cl2], respectively, which have been determined by X‐ray crystallography. Both of them can serve as catalysts for electrochemical and photochemical driven hydrogen evolution. Under an overpotential (OP) of 837.6 mV, [Cu(btep)Br2] or [Cu(btep)Cl2] can electrocatalyze hydrogen evolution from a neutral water with a turnover frequency (TOF) of 373 and 120 mol of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h), respectively. Under blue light, mixing with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, the photolysis of an aqueous solution (pH 4.5) with [Cu(btep)Br2] or [Cu(btep)Cl2] can provide 6180 and 5120 mol of H2 per mole of catalyst (mol of H2 (mol of cat)−1) during 48‐h irradiation with an average apparent quantum yield of 16.7% and 11.0%, respectively. The results show that [Cu(btep)Br2] shows a more efficient activity for H2 generation than [Cu(btep)Cl2]. Several electrochemical and photochemical measurements and analysis are carried out to study catalytic mechanism for H2 production. [ABSTRACT FROM AUTHOR]

We have meticulously designed a triple S-Scheme intermolecular g-C 3 N 4 homojunction that boasts a robust built-in electric field and facilitates charge transfer. Importantly, the nature of the built-in electric field and the mechanism for enhanced photocatalytic hydrogen evolution are profoundly revealed. [Display omitted] • A triple S-Scheme intermolecular carbon nitride homojunction is prepared. • Enhancement of BIEF through molecular-level domains promoted carrier separation. • PHE rate of UTMCN is about 38.9 times higher than that of pristine g-C 3 N 4. • Enhanced mechanism of PHE activity is insightfully elucidated. Photocatalytic hydrogen evolution (PHE) from water using graphitic carbon nitride (gCN) is considered a promising way to approach the energy crisis. Homojunction photocatalysts, especially intermolecular homojunction, provide an ideal candidate for photocatalytic hydrogen production. Here, we employ an eutectic salt-assisted thermal polymerization strategy to create a novel ternary gCN homojunction photocatalyst (denoted as UTMCN). The molecular-level contacts across components promote rapid charge carrier transfer and separation. Meanwhile, the fluctuation of the composition within the conjugate plane results in a unique triple S-Scheme energy band arrangement, thus possessing a more than tenfold enhanced built-in electric field (BIEF), and also leads to the separation of the active center. At the same time, the adsorption-free energy of the intermediate hydrogen species (H*) is reduced, thus promoting proton reduction kinetics. As expected, the UTMCN exhibits outstanding photocatalytic performance, which is 38.9 times that of intrinsic carbon nitride. Importantly, the mechanism for the enhanced BIEF to promote PHE performance is elucidated in detail. This work guides the rational construction of intermolecular homojunction with a robust BIEF to improve the performance of PHE. [ABSTRACT FROM AUTHOR]

Graphdiyne (GD), a novel two‐dimension carbon hybrid material, due to its unique and excellent properties, has been widely concerned since this innovative material was successfully synthesized by Prof. Yuliang Li in 2010. Traditionally, its synthesis method is growing graphdiyne on copper foils or foam copper as a base catalytic material to deliver copper ions (Cu2+) under pyridine conditions. Here, an innovative progress for graphdiyne preparation approach of using Cu+ ion as a catalytic material is reported and its application in extending to the photocatalytic water‐splitting to produce hydrogen in situ as well. In detail, by means of cuprous iodide used as a catalyst‐carrier to grow a graphdiyne in a pyridine solution of monomeric hexynylbenzene and such CuI‐graphdiyne composite catalyst is directly applied to photocatalytic hydrogen production in situ. Meanwhile, the hydrogen production of GD and CuI are 29.42 μmol/5 h and 156.49 μmol/5 h, respectively. In particular, the composite catalyst GD‐CuI exhibits an optimum photo‐catalytic hydrogen production activity (465.95 μmol/5 h) which is 15.8 times and 3.0 times that of pure GD and CuI respectively. This rational design, one‐step construction of GD‐CuI, successfully enhances photo‐catalytic hydrogen evolution activity. The deeper characterization study results such as TEM, SEM, XPS, XRD, UV‐vis DRS, Transient photocurrent and FT‐IR etc. have been well researched and the results of which are in good agreement with each other. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Monolithic etched copper foam-based Cu 2 O Layer/TiO 2 nanodots heterojunction electrode is prepared. • The optimized electrode shows interface charges redistribution and appropriate H 2 O and H adsorption free energy. • Excellent HER electrocatalytic activity comparable to Pt's is obtained. Abstract Semiconducting materials are considered as excellent electrocatalysts for electrochemical water splitting; however, there is still a lack of relevant design and understanding of semiconducting composite electrodes. Here, a monolithic electrode composed of etched copper foam and p-n heterojunction (p-type Cu 2 O layer and n-type TiO 2 nanodots with excellent hydrophilicity) is successfully prepared. This can reduce the electron transfer resistance, optimize water and H adsorption on catalyst surface and generate a space-charge region in phase interface, enhancing the local electrons density of Cu 2 O, which is proved by experimental results and density functional theory (DFT). Owing to the whole accelerated Volmer-Heyrovsky pathway, the as-prepared heterojunction electrode exhibits low onset potential (18 mV), high electrocatalytic activity (a potential of 114 mV at 10 mA cm−2) and long-term stability for hydrogen evolution reaction in alkaline media that is comparable to that of Pt, enabling the large scale fabrication. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 2 N nanoparticles was grown on carbon cloth for Li-ion batteries. • Free-standing Fe 2 N Nanoparticles achieved excellent Li storage performance. • The mechanism of intercalation for Li-ion was studied in-depth. Herein, we systemically studied the storage mechanism and effect of lithium ion (Li-ion) intercalation in Fe 2 N nanoparticles grown on carbon cloth using ex-situ characterizations including X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results confirm the conversion storage mechanism of the Fe 2 N as anode material for lithium ion batteries (LIBs). This study will provide valuable insights toward understanding Li-ion storage to other transition metal nitrides for LIBs. [ABSTRACT FROM AUTHOR]

Noble metal-free Ni-Mo-S nanoparticles modified graphitic C 3 N 4 for efficient hydrogen evolution was successfully synthesized by means of a simple hydrothermal ion exchange process. This composite photocatalyst exhibits about 14 times higher photocatalytic activity of hydrogen production than that of the pure g-C 3 N 4 . Fluorescence analysis and electrochemical characterization confirmed that molybdenum sulfide and nickel sulfide as catalyst significantly enhanced the transfer of electrons on g-C 3 N 4 and resulted in the excellent synergistic effect in photocatalytic properties. The promoted charge separation was measured by means of the EIS, photocurrent and transient fluorescence. A series of studies shown that the Ni x Mo 1-x S 2 nanoparticles modified on the surface of graphitic C 3 N 4 provided the more active sites and improved the efficiency of photo-generated charge separation with several characterizations such as SEM, XRD, XPS, element mapping, UV–vis DRS, Transient photocurrent and BET etc . and the results of which were in good agreement with each other. The composite photocatalyst g-C 3 N 4 /Ni x Mo 1-x S 2 has a greater specific surface area and pore volume compared to pure g-C 3 N 4 , which is more favorable for the adsorption of dye molecules, leading to enhance the composite photocatalytic activity consequently. The excited-electron recombination process were greatly modulated with the introduce Ni-Mo-S nanoparticles on the surface of g-C 3 N 4 and the photostability was enhanced as well. In addition, a possible reaction mechanism over eosin Y-sensitized g-C 3 N 4 /Ni x Mo 1-x S 2 photocatalyst under visible light irradiation was proposed. [ABSTRACT FROM AUTHOR]

• 2,6-pyridinedicarboxylic acid (H 2 L) reacts with NiCl 2 to afford a new nickel(II) complex, [Ni(HL) 2 ]. • [Ni(HL) 2 ] can efficiently electro-catalyze H 2 evolution from acetic acid with a rate constant of 3454 M−2 s−1. • [Ni(HL) 2 ] also can efficiently electro-catalyze H 2 oxidation with a rate constant of 2.047 × 104 M−2 s−1. A new electrocatalyst based on a nickel complex, [Ni(HL) 2 ], is designed and provided by the reaction of NiCl 2 with 2,6-pyridinedicarboxylic acid (H 2 L) in our group. Electrochemical investigations show that [Ni(HL) 2 ] can electro-catalyze hydrogen evolution from acetic acid with a rate constant of 3454 M−2 s−1. [Ni(HL) 2 ] also can electro-catalyze hydrogen oxidation with a rate constant of 2.047 × 104 M−2 s−1. The carboxyl group of [Ni(HL) 2 ] may play critical roles in the catalytic hydrogen evolution and oxidation reactions. Moreover, the introduction of an electron-withdrawing group, -Cl at the pyridine of H 2 L leads to a decrease in the catalytic activity for hydrogen generation, and [Ni(HL) 2 ] shows a more efficient activity than [Ni(HL-Cl) 2 ] (H 2 L-Cl: 4-chloro-2,6-pyridinedicarboxylic acid). These findings can afford a new ideal for the design of electrocatalysts for both H 2 evolution and H 2 oxidation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The reaction of H 2 ATSE with Pd(CH 3 CN) 2 Cl 2 affords a new palladium complex, Pd-ATSE, which has been characterized by physico-chemical and spectroscopic methods. EPR investigations show that there are the couplings of 105Pd with the neighboring 14N and 33S nuclei from the ATSE2- ligand. Under an overpotential of 837.6 mV, Pd-ATSE can afford 666 mol of hydrogen per mole of catalyst per hour. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) and ascorbic acid (H 2 A), Pd-ATSE can catalyze hydrogen generation with a turnover number (TON) of 3520 mol H 2 per mol of catalyst (mol of cat−1) during 28 h irradiation. [ABSTRACT FROM AUTHOR]

The molecular nickel catalysts exhibits good activity in both electrocatalytic and photocatalytic hydrogen evolution reaction. As a co-catalyst, Ni-SAO also can contribute to enhanced activity by receiving photoelectrons produced by CdS nanorods (CdS NRs), a photosensitizer under visible light (λ = 469 nm). [Display omitted] • A new nickel complex has been synthesized and characterized. • At OP of 837.6 mV, Ni-SAO can electrocatalyze HER with a TOF of 1428 h−1. • As co-catalyst, Ni-SAO also can photo-catalyze H 2 evolution with a TON of 8138 after 48 hours irradiation. A square planar nickel complex bearing salicylketoxime (SAO), Ni-SAO has been synthesized and well characterized by ESI-MS and single-crystal X-ray diffraction, etc. Ni-SAO exhibits good activity in both electrocatalytic and photocatalytic hydrogen evolution reaction (HER). Under an overpotential (OP) of 837.6 mV, Ni-SAO can electrocatalyze hydrogen evolution from a neutral aqueous buffer with a turnover frequency (TOF) of 1428 mol of hydrogen per mole of catalyst per hour (mol H 2 /mol catalyst/h). Moreover, under blue light (λ = 469 nm), a three-component system containing Ni-SAO as a catalyst, CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H 2 A) as a sacrificial electron donor also can afford hydrogen with a turnover number (TON) of 8138 mol H 2 per mol of catalyst (mol of cat−1) during 48 h irradiation. The highest apparent quantum yield (AQY) is about 16.5% at 469 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • en-P 2 reacts with Cu(ClO 4) 2 or CuClO 4 to afford [CuII-en-P 2 (NCMe)](ClO 4) 2 1 and [CuI-en-P 2 ]ClO 4 2. • The addition of Cu2+ or Cu+ leads to a decrease on photoluminescence of en-P 2. • 1 shows a more efficient activity for hydrogen evolution than 2. Reactions of N,N'-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P 2) with Cu(ClO 4) 2 or CuClO 4 afford two complexes, [CuII-en-P 2 (NCMe)](ClO 4) 2 1 and [CuI-en-P 2 ]ClO 4 2 , respectively, which have been characterized by several physico-chemical and spectroscopic methods. The copper atom is five, and four-coordinated in the copper complexes 1 and 2 , respectively. At room temperature, en-P 2 shows photoluminescence at 420 and 560 nm, however, the addition of Cu2+ or Cu+ leads to a decrease on the peak intensities at 420 and 560 nm, respectively. Investigations for magnetic behaviors show that upon cooling from 300 to 2 K, the χ M T value of both copper complexes 1 and 2 steadily increased. Additionally, electrochemical investigations reveal that both complexes 1 and 2 have electrocatalytic activity for hydrogen evolution from acetic acid or water, and complex 1 shows a more efficient activity than complex 2. [ABSTRACT FROM AUTHOR]

A new catalyst for both water reduction and oxidation, based on an infinite chain, {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n , is formed by the reaction of NiCl 2 , 1,3-propanediamine (tn) and K 3 [Fe(CN) 6 ]. {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n can electro-catalyze hydrogen evolution from a neutral aqueous buffer (pH 7.0) with a turnover frequency (TOF) of 1561 mol of hydrogen per mole of catalyst per hour (H 2 /mol catalyst/h) at an overpotential (OP) of 837 mV {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n also can electro-catalyze O 2 production from water with a TOF of ∼45 mol O 2 (mol cat)−1s−1 at an OP of 591 mV. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H 2 A) as a sacrificial electron donor, {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n can photo-catalyze hydrogen generation from an aqueous buffer (pH 4.0) with a turnover number (TON) of 11,450 mol H 2 per mole of catalyst (mol of H 2 (mol of cat)−1) during 10 h irradiation. The average of apparent quantum yield (AQY) is as high as 40.96% during 10 h irradiation. Studies indicate that {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n exists in two forms: a cyano-bridged chain ({[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n) in solid, and a salt ([Ni(tn) 2 ] 3 [Fe(CN) 6 ] 2) in aqueous media; Catalytic reaction occurs on the nickel center of [Ni(tn) 2 ]2+, and the introduction of [Fe(CN) 6 ]3- can improve the catalytic efficiency of [Ni(tn) 2 ]2+ for H 2 or O 2 generation. We hope these findings can afford a new method for the design of catalysts for both water reduction and oxidation. [Display omitted] • Reaction of NiCl 2 , tn and K 3 [Fe(CN) 6 ] affords a complex, {[Ni(tn) 2 ] 3 [Fe(CN) 4 (μ-CN) 2 ] 2 } n 1. • 1 electrocatalyzes H 2 generation from water with a TOF of 1561 mol H 2 /mol catalyst/h at OP of 837 mV. • 1 electrocatalyzes O 2 generation from water with a TOF ∼45 mol O 2 (mol cat)−1s−1 at OP of 591 mV. • 1 can photo-catalyze hydrogen generation with a TON of 11,450 mol of cat−1 during 10 h irradiation. • The average of AQY is up to 40.96% during 10 h irradiation. [ABSTRACT FROM AUTHOR]

[Display omitted] Valence modulation of transition metal oxides represents a highly effective approach in designing high-performance catalysts, particularly for pivotal applications such as the hydrogen evolution reaction (HER) in solar/electric water splitting and the hydrogen economy. Recently, there has been a growing interest in high-valence transition metal-based electrocatalysts (HVTMs) due to their demonstrated superiority in HER performance, attributed to the fundamental dynamics of charge transfer and the evolution of intermediates. Nevertheless, the synthesis of HVTMs encounters considerable thermodynamic barriers, which presents challenges in their preparation. Moreover, the underlying mechanism responsible for the enhancement in HVTMs still needs to be discovered. Hence, the universal synthesis strategies of the HVTMs are discussed, and direct Raman spectroscopic evidence for intermediates regulation is revealed to guide the further design of the HVTM electrocatalysts. This work offers new insights for facile designing of HVTMs electrocatalysts for energy conversion and storage through adjusting the reaction pathway. [ABSTRACT FROM AUTHOR]

The challenge in the artificial CO2 reduction to fuel is achieving high selective electrocatalysts. Here, a highly selective Cu2O/CuO heterostructure electrocatalyst is developed for CO2 electroreduction. The Cu2O/CuO nanowires modified by Ni nanoparticles exhibit superior catalytic performance with high faradic efficiency (95% for CO). Theoretical and experimental analyses show that the hybridization of Cu2O/CuO nanowires and Ni nanoparticles can not only adjust the d‐band center of electrocatalysts to enhance the intrinsic catalytic activity but also improve the adsorption of COOH* intermediates and suppress the hydrogen evolution reaction to promote the CO conversion efficiency during CO2 reduction reaction. An in situ Raman spectroscopic study further confirms the existence of COOH* species and the engineering intermediates adsorption. This work offers new insights for facile designing of nonprecious transition metal compound heterostructure for CO2 reduction reaction through adjusting the reaction pathway. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tuning practical metal electrode potentials by molten salt way can assemble bimetal hydroxide nanosheet array on substrates. • Metal redox chemistry and nonmetallic lattice oxygen in active phases are highly activated. • Decent OER behavior and stability at industrial-level current density are obtained. • Various hydrous-molten salts can be extended to fast erode different metal foams into robust electrocatalysts. Durable, active, and cheap oxygen evolution reaction (OER) electrocatalyst to replace the noble metal-based ones is appealing but challenging in energy storage fields. Here, we devise a one-pot low-temperature hydrous molten salt erosion strategy to vertically root the thin and dense bimetal hydroxide (NiFeO x H y) nanosheet on commercial nickel foam in 1 min. The defect-rich nanosheets are interdigitated together to yield a highly porous array, which offers affluent exposed electroactive centers, decreased charge/mass transfer, and augmented mechanical stability, while a strong Ni-Fe synergy elicits the signal redox reactivity of both metal and nonmetal lattice oxygen. Due to such effects, the typical NiFeO x H y electrode accesses a catalytic current of 10 mA cm−2 at a low overpotential 216 mV for freshwater electrolyte and 232 mV for saline one both with a small Tafel slope of 53 mV dec−1, while stably working for 1000 h at 0.1 A cm−2 in freshwater electrolyte and over 550 h at 1 A cm−2 in saline one. This evidences efficient and stable large-current–density OER performance, particularly a strong Cl− anti-erosion. The large-scale NiFeO x H y electrode materials (81 cm2) with a commensurate performance are fabricated on nickel foam, heralding the enormous prospect for practical usage. This exceedingly procedure-, energy- and time-saving erosion tactic can be generalized to common metal foam substrates and hydrous metal molten salts, accenting a momentous stepping stone for integral construction of self-supported and large-size electrodes towards commercially-met OER application and beyond. [ABSTRACT FROM AUTHOR]

Fabricating environmental and stable graphitic carbon nitride (g-C 3 N 4) photocatalyst with highly efficient visible light response and charge separation is still a challenging work. Herein, g-C 3 N 4 ultrathin nanosheets are synthesized via oxidation etching method. The as-synthesized samples show improved visible-light response and photogenerated charge separation, which is revealed to be brought from the synergy of hierarchical porous structure and nitrogen vacancies. On one hand, macropores can provide light transport channels for enhanced visible light absorption, meanwhile the photogenerated charge favors to be migrated on two-dimensional ultrathin planes and trapped in mesoporous structure to avoid the recombination. Also, macropore and mesopore promote the transport and adsorption of substrates. On the other hand, DFT calculations verify that nitrogen vacancies are conductive to the rearrangement of charge density distribution and the formation of defect levels in the band gap of g-C 3 N 4 , leading to the improvement of carrier mobility and separation. Thus, nitrogen vacancies promote more active sites generation. Consequently, the g-C 3 N 4 ultrathin nanosheet presents a promising photocatalytic hydrogen evolution rate of 1.77 mmol.g−1.h−1 in a long time run under visible light, which is far higher than that of comparison samples (0.18 and 0.29 mmol.g−1.h−1 respectively). Highly efficient photocatalytic hydrogen evolution activity from the hierarchical pores and nitrogen vacancies in carbon nitride ultrathin nanosheets (TCN) is uncovered. The macropore provide channels for light absorption and reactant transport, and mesoporous work as active sites for electron trap and reactant adsorption. Meanwhile, nitrogen vacancies induce the rearrangement of electrons and the formation of defect levels, leading the improvement of carrier mobility and separation. Accordingly, photocatalytic activity of TCN is enhanced to an order of magnitude than that of bulk CN. [Display omitted] • Hierarchical pores and nitrogen vacancies are fabricated in TCN ultrathin nanosheet. • The hierarchical pores can provide the light and reactant channels and active sites. • The energy-level modulating mechanism by nitrogen vacancies has been revealed. • Trap for photogenerated charge is formed by nitrogen vacancies. • The photocatalytic activity of TCN is elevated to an order of magnitude. [ABSTRACT FROM AUTHOR]

Special enhanced synergetic effect of MoS 2 quantum dots (MoS 2 QDs) and graphene on metal-organic frameworks for photocatalytic hydrogen evolution is obtained here. The photocatalytic activity of H 2 evolution reach 186.37 μmol over the EY-sensitized 5 wt % MoS 2 QDs/UiO-66-NH 2 /G irradiated under visible light irradiation (λ ≥ 420 nm) in the first 3 h, and the apparent quantum efficiency (AQE) is 40.5% at 430 nm. The synergistic effect between MoS 2 QDs and graphene together with UiO-66-NH2 is corroborated by photo-luminescence spectra, electro-chemical and photo-electro-chemical experiments. It demonstrate that the charge separation and the electrons transfer are more efficient with the aid of the MoS 2 QDs and graphene. MoS 2 QDs might be a potential photocatalyst for design new type of catalysts in photocatalysis proton reduction. [ABSTRACT FROM AUTHOR]

The hydrazine oxidation reaction (HzOR) has been considered as a more energy-efficient alternative to the oxygen evolution reaction in water electrolysis. To design efficient electrocatalysts for HzOR, precise engineering of materials is required to increase active sites and build electronic structures. Herein, nitrogen contained face-centered cubic rhodium (N-fcc-Rh) nanosheets are prepared by directly annealing metastable trigonal rhodium oxide precursor in the ammonia atmosphere. Benefiting from the abundant active sites and unique electronic structure, the optimal N-fcc-Rh-300 electrocatalyst achieves an ultra-low working potential of − 81 mV (vs. RHE) at 10 mA cm−2 in 1.0 M KOH/0.5 M N 2 H 4. Density functional theory calculations suggest the N element in the N-fcc-Rh electrocatalyst enables to the reduction of the formation energy of the potential-determining step from *NH 2 NH 2 to *NHNH 2 for the HzOR process. This work reveals a new strategy to prepare advanced metal electrocatalysts for various electrochemical applications. [Display omitted] • Nitrogen contained face-centered cubic rhodium nanosheets. • Excellent HzOR activity with working potential of − 81 mV (vs. RHE) at 10 mA cm−2. • N elements into Rh leads to a shift of the d-band center away from the Fermi level. [ABSTRACT FROM AUTHOR]

3R-phase iridium oxide with superior ORR activity was obtained by intercalating a tiny amount of Pt into its interlayers. A mechanism that intercalates Pt atoms into the interlayer of 3R-IrO 2 enables to activate the ORR activity of the passivated Ir atoms in 3R-IrO 2 is proposed to further understand the real active center for precious metal-intercalated metal oxide electrocatalysts. [Display omitted] • Pt-intercalated 3R-phase iridium oxide is fabricated at normal temperature. • 3R-IrO 2 with high ORR activity by intercalating 3.6 %Pt into the interlayers. • The active center of Pt-3R-IrO 2 in ORR is the Ir sites rather than the Pt sites. Iridium oxide (IrO 2) has traditionally been considered to exhibit limited oxygen-reducing capacity. An effective approach to improve the oxygen reduction reaction (ORR) activity in parent catalytic materials is through atomic intercalation. However, the challenge lies in achieving a delicate balance between high ORR activity, structural stability, and minimizing the use of precious metals. Herein, we fabricate 3R-phase iridium oxide (3R-IrO 2) with superior ORR activity by intercalating a tiny amount of Pt (3.6 wt% Pt) into the interlayers of 3R-IrO 2 (3.6 wt% Pt-3R-IrO 2). When employed as an acidic ORR electrocatalyst, 3.6 wt% Pt-3R-IrO 2 shows a high half-wave potential (E 1/2) of 0.92 V (vs. RHE) in O 2 -saturated 0.1 M HClO 4 electrolyte, much better than those of Pt/C (0.850 V), 3R-IrO 2 (0.616 V), and Pt nanoparticles on 3R-IrO 2 surface (3.6 wt% Pt@3R-IrO 2) (0.618 V) electrocatalysts. It achieves high mass activity of 0.170 A mg Ir −1 at the potential of 0.9 V, which is 5.5 and 11.3 times than that of Pt/C (0.031 A mg Ir −1) and 3.6 wt% Pt@3R-IrO 2 (0.015 A mg Ir −1), respectively. Density functional theory (DFT) calculations and experiment results co-jointly demonstrate that the active center of Pt-3R-IrO 2 is anchored to the activated Ir atoms of the 3R-IrO 2 rather than Pt atoms. The d -band center of Ir 5 d orbitals of Pt-3R-IrO 2 is simultaneously regulated, which optimizes the energy barrier of adsorption/desorption toward the ORR process. Intriguingly, the intercalation of Pt atoms into trigonal rhodium oxide (Tri-RhO 2) also activates the ORR activity of Rh, suggesting the universality of this strategy. This discovery may provide a new and general way for activation of ORR activity of other precious metal-intercalated nonprecious metal oxide electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterogeneous ZnSe-MnSe nanocomposite is synthesized. • The nanohybrid exhibits superior electrocatalytic activity for both HER and EOR. • The heterostructure not only boosts H* desorption, but also favors EtOH adsorption. • Ethanol-assisted water electrolysis shows lower energy consumption. The combination of the dual sites of hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR) into a single electrocatalyst is indispensable for energy-saving hydrogen generation. However, such combination is hindered for practical applications due to the challenges regarding fewer active sites on electrocatalysts. Herein, we prepared a heterogeneous nanostructure comprising of ZnSe and MnSe embedded in nitrogen-doped carbon (namely ZnSe-MnSe), where the Mn elements can be controllably introduced into ZnSe to modulate the electronic states and thus boost the charge transfer from MnSe to ZnSe. The interfacial electronic regulation stimulates the formation of well-defined HER and EOR active centers, which could optimize hydrogen adsorption energy and ethanol adsorption property, thus fulfilling superior HER and EOR performances. Specifically, due to the more propitious thermodynamics and kinetics of EOR triggered by ZnSe-MnSe electrocatalyst than those of OER, the demanded cell potential of ethanol-assisted water electrolysis is markedly lower than water electrolysis. Besides, the oxidation product ethyl acetate in this case is more valuable than oxygen from water electrolysis. This work presents a promising tactic in designing future energy-saving hydrogen generation applications and related high-performance electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new hybrid with Cu-doped ZnSe nanogranules embedded in N-doped carbon is prepared. • Heteroatom Cu not only favors O–H bond cleavage, but also boosts hydrogen desorption. • Cu-ZnSe@NC shows faster kinetics and lower overpotential than the pristine ZnSe@NC. Effective electronic modulation is the key to fulfilling the Pt-like hydrogen evolution reaction (HER) activity on selenide-based electrocatalysts, but it also brings a huge challenge to rational structural design. Zinc selenide (ZnSe) is a potential candidate for alkaline HER. However, much fewer endeavours have been dedicated to ZnSe, hence inherent activities still need to be enhanced via facilitating the Volmer and Heyrovsky steps. Herein, we developed a simple fabrication method for copper-doped ZnSe nanoparticles embedded in nitrogen-doped carbon (namely Cu-ZnSe@NC) from bimetallic ZnCu-ZIF to promote alkaline HER. Benefitting from three-dimensional porous morphology and modulated electronic structure, the Cu-ZnSe@NC displays superior HER performance with small overpotential of 84 mV at the current density of 10 mA cm−2, comparable to that of commercial Pt/C. Experimental and theoretical results demonstrate that the incorporation of heteroatom-Cu can not only increase the number of active sites and improve the intrinsic activity of each catalytic site, but also modulate the electronic structure of the catalyst, which is advantageous to boosting H 2 O adsorption and optimizing the energy barrier for H adsorption for initiating the electrocatalytic pathway at alkaline electrolyte. This work provides a novel understanding for designing of selenide-based composite for HER with improved catalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The porous rhodium nanosheets with tunable compressive strain were successfully obtained by directly annealing metastable trigonal rhodium oxide. • The record HzOR performance. • A clear strain effect and catalytic mechanism for alkaline HzOR in single-metal-element systems. Electrocatalytic water decomposition is an essential pathway for large-scale preparation of high-purity hydrogen, while the conventional oxygen evolution reaction (OER) with a kinetically sluggish four-electron process becomes a huge challenge for its further application. Hydrazine oxidation reaction (HzOR) is considered an effective strategy to replace the sluggish OER process, attributed to its lower thermodynamic oxidation potential. Here, porous rhodium nanosheets (Rh-NSs) with tunable lattice strain are successfully obtained by directly annealing metastable trigonal rhodium oxide (Tri-RhO 2) in a hydrogen atmosphere. More importantly, ligand and synergetic effects can be effectively avoided in a single-metal-element system, providing an ideal model electrocatalyst for understanding the correlation between reactivity and lattice strain. The electrochemical results show that the optimal Rh-NSs-300 (the Tri-RhO 2 precursor is annealed at 300 °C) may deliver ultralow working potential (vs. RHE) of −103 mV at the current density of 10 mA cm−2 with a Tafel slope of 15.4 mV dec-1 for HzOR. In addition, the working potential (vs. RHE) of Rh-NSs-300 only drops 35 mV after the 72 h test by chronopotentiometry method at the constant current density of 10 mA cm−2. Density functional theory (DFT) calculations indicate that HzOR can more easily occur on Rh-NSs with tunable compressive strain than pure Rh. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is a promising route to produce hydrogen under mild conditions. Local reaction environment regulation via electrochemical activation is one of the most promising ways to achieve excellent hydrogen evolution reaction (HER) catalytic activity. Electrochemical activation technology compared with traditional synthetic technology has many advantages, such as low energy consumption, fast reaction speed, simple experimental operation, and reducing energy and environmental problems. However, the mechanism of adjusting the local reaction environment remains unclear. Here, we use a simple electrochemical activation method to control the Ni 5 P 4 particles on the nickel surface to achieve the regulation of the local reaction environment. It is found that electrochemical activation could effectively improve the catalytic activity, with hydrogen evolution overpotential of 87 mV at 10 mA cm−2. Both electrochemical measurements and theoretical calculation demonstrate the important role of in situ electrochemical activations for intermediate adsorption and desorption via nickel coordination regulation. Our strategy of adjusting the local reaction environment with nickel coordination regulation merging interfacial may create a promising pathway to developing the HER performance of metal phosphide. [Display omitted] • Electrochemical activation was used for Ni coordination regulation. • Ni with Ni 5 P 4 particles exhibits excellent HER activity. • Local reaction environment adjusting mechanism was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultrafast method is developed to synthesize Cu 2 O octahedrons. • Highly dispersed Cu 2 O octahedrons inlaid in Ni Foam are obtained. • The sample displays superior catalytic activity in both alkaline water/seawater electrolytes. • The sample exhibits good catalytic durability and stability. Development of bifunctional cost-effective and self-supporting electrocatalysts for high-performance water/seawater electrolysis are vital for emerging energy storage and conversion technologies. Herein, an ultrafast strategy is reported to synthesis homogeneous Cu 2 O octahedrons inlaid in Ni foam (oct_Cu 2 O-NF) via spontaneous replacement of Ni with Cu, followed by rapid oxidization of Cu in air. Benefiting from the high dispersion of uniform octahedral structure and strong interaction between Cu 2 O and Ni foam, oct_Cu 2 O-NF displayed a superior activity for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) as well as outstanding stability. After assembling oct_Cu 2 O-NF as bifunctional electrodes for alkaline seawater splitting, the electrolyzer exhibited a very small cell voltage of 1.71 V to reach 10 mA cm−2. This brand-new way of ultrafast synthesis for oct_Cu 2 O-NF experimentally confirms the feasibility of Cu-based nanomaterials for efficient water/seawater electrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core-double-shell architecture was designed as efficient HER and OER electrocatalysts. • Cobalt phosphide and NiFe-LDH were used as representative HER and OER catalysts. • The architecture consist of core–shell porous carbon fiber (CFC@EC) and TMCs. • Lattice distortions were created in the TMCs by CFC@EC, facilitating the exposure of active sites. • Enhanced performance is due to the strong electronic interaction between the hybrids. Different transition metal compounds (TMCs) nanostructures grown on conductive substrates have been considered as promising self-supportive non-precious electrocatalysts for electrochemical water splitting, but extremely challenging to develop facile and generalized approaches for rational design and enhancing their catalytic properties. Herein, we develop a general strategy to boost the hydrogen and oxygen evolution reactions (HER and OER) performance of TMCs by designing monolith electrocatalyst architectures. The monoliths comprises of TMCs integrated on carbon fiber cloth core–shell (CFC@EC) structure. The CFC@EC allows the creation of numerous lattice distortions and strong electronic interactions between CFC@EC and metal cations of the TMCs. Such lattice distortions exposes more active sites in CFC@EC/TMCs compared to the pristine CFC coated TMCs (CFC/TMC). Cobalt phosphide (CoP) nanowires and NiFe-LDH coated on CFC@EC exhibits the optimized HER and OER activities. Overall water splitting device assembled based on the optimized HER and OER electrodes also achieve low overall potential of 1.53 V at 10 mA cm−2. More importantly, we further experimentally verify that the integration of Ni 3 N and Ni 3 S 2 , CoS 2 , NiCo-LDH, NiMn-LDH with CFC@EC also reveal similar improved performance, providing a general and valuable strategy into the design of other self-supporting electrocatalysts for water splitting and beyond. [ABSTRACT FROM AUTHOR]