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Electrocatalytic water splitting is an effective strategy, which can convert intermittent energy such as wind energy and solar energy into renewable and sustainable hydrogen energy. Global freshwater resources are extremely scarce. Compared with freshwater, seawater is a rich and sustainable resource, and it has attracted more and more attention in electrocatalysis. However, the oxygen evolution reaction (OER) is a four‐electron transfer process, which leads to slow reaction kinetics. Moreover, the presence of various elements in seawater and their interference to electrochemistry make the OER in seawater extremely challenging. Herein, the latest progress in the development of transition metal‐based OER electrocatalytic materials for seawater is reviewed by hydroxides, oxides, chalcogenides, phosphides, and nitrides. Focus is made on how to eliminate competitive reaction chlorine evolution reaction of OER in electrolytic seawater. The recent research advances of OER catalyst for selective electrolysis seawater are summarized from the aspects of structure design, mechanism understanding, and performance enhancement strategy. Finally, the challenges, prospects, and research directions of seawater electrocatalysis for OER are introduced. [ABSTRACT FROM AUTHOR]

Transition‐metal phosphates have been widely applied as promising candidates for electrochemical energy storage and conversion. In this study, we report a simple method to prepare a N, F co‐doped mesoporous cobalt phosphate with rich‐oxygen vacancies by in‐situ pyrolysis of a Co‐phosphate precursor with NH4+ cations and F− anions. Due to this heteroatom doping, it could achieve a current density of 10 mA/cm2 at lower overpotential of 276 mV and smaller Tafel slope of 57.11 mV dec−1 on glassy carbon. Moreover, it could keep 92 % of initial current density for 35 h, indicating it has an excellent stability and durability. Furthermore, the optimal material applied in supercapacitor displays specific capacitance of 206.3 F g−1 at 1 A ⋅ g−1 and maintains cycling stability with 80 % after 3000 cycles. The excellent electrochemical properties should be attributed to N, F co‐doping into this Co‐based phosphate, which effectively modulates its electronic structure. In addition, its amorphous structure provides more active sites; moreover, its mesoporous structure should be beneficial to mass transfer and electrolyte diffusion. [ABSTRACT FROM AUTHOR]

A catalyst based on [LCo(H2O)] (1) is formed by the reaction of dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methyl)phenol (H2L) with CoBr2for electrolytic proton or water reduction.1catalyzes hydrogen evolution, both from acetic acid with a turnover frequency (TOF) of 17.9 mol of hydrogen per mole of catalyst per hour at an overpotential of 792 mV (in DMF) and from water with a TOF of 260 mol of hydrogen per mole of catalyst per hour at an overpotential of 889 mV (in buffer, pH 7.0). [ABSTRACT FROM AUTHOR]

The reaction of 1-[(2-carboxymethyl)benzene]-3-[2-pyridine]triazene (HL) with CoCl 2 · 6H 2 O affords a six-coordinated cobalt(III) complex, [CoL 3 ] 1 , a new molecular electrocatalyst. Electrochemical studies show that complex 1 can catalyze hydrogen evolution from both acetic acid and water. Turnover frequency (TOF) reaches a maximum of 21 and 1973 mol of hydrogen per hour at overpotential (OP) of 992 mV (in DMF) and 838 mV (in phosphate buffer, pH 7.0), respectively. This performance is significantly better than those of other molecular cobalt catalysts reported in the literature for electrochemical hydrogen production. This is attributed to the ionic ligand, L − that coordinates strongly through four nitrogen atoms to the cobalt center, stabilizing the low oxidation state. [ABSTRACT FROM AUTHOR]

A new molecular catalyst based on a dinuclear iron complex [L 2 Fe 2 (CH 3 O) 2 ] 1 is formed by the reaction of 2-pyridylamino-N,N-bis(2-methylene-4,6-bimethyl)phenol (H 2 L) with FeCl 3 for electrolytic hydrogen evolution both from acetic acid and water. Turnover frequency (TOF) reaches a maximum of 84.5 mol of hydrogen per mole of catalyst per hour at an overpotential of 941.6 mV (in DMF) and 1076.5 mol of hydrogen per mole of catalyst per hour at an overpotential of 896.8 mV (in buffer, pH 7.0), respectively. Sustained water reduction catalysis occurs at glassy carbon to give H 2 over a 1 h electrolysis period with 94.5% Faradaic yield. [ABSTRACT FROM AUTHOR]

Reaction of FeCl 3 with 2-pyridylamino- N -2-methylene-4-ethyl-6- tert -butylphenol, N′- 2-methylene-4-methyl-6- tert -butylphenol (H 2 L) affords an iron(III) complex, [LFeCl] 1 , which has been characterized by UV–Vis spectrum and X-ray crystallography. Turnover frequency (TOF) for hydrogen evolution reaches a maximum of 141 moles of hydrogen per mole of catalyst per hour at an overpotential of 878.6 mV (in buffer, pH 7.0). Sustained water reduction catalysis occurs at glassy carbon to give H 2 over a 3 h electrolysis period with 93% faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

The reaction of 1-[(2-carboxyethyl)benzene]-3-[benzothiazole]triazene (HL) and CuCl gives a trinuclear copper(I) complex, [Cu I 3 (L)(L′) 2 ]·THF ( 1 ·THF) (L′ = the 1-[(2-carboxymethyl)benzene]-3-[benzothiazole]triazene ion), which has been structurally characterized by X-ray crystallography. Electrochemical studies indicate that this complex can catalyze hydrogen evolution from a neutral buffer with a turnover frequency of 355 (pH 7.0) moles of hydrogen per mole of catalyst per hour at an overpotential of 789 mV vs SHE. Sustained proton reduction catalysis occurs at a glassy carbon (GC) electrode to give H 2 over a 72 h electrolysis period with 94.4% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

Splitting water is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for these reactions, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Until now, there is as yet no report on both water oxidation and reduction by identical catalyst. Reported here is the first soluble copper-based catalyst, Cu(Me 2 oxpn)Cu(OH) 2 ] 1 (Me 2 oxpn: N,N′-bis(2,2′-dimethyl-3-aminopropyl)oxamido) for both electrolytic water oxidation and reduction. Water oxidation occurs at an overpotential of 636 mV vs SHE to give O 2 with a turnover frequency (TOF) of ∼2.14 s −1 . Electrochemical studies also indicate that 1 is a soluble molecular species, that is among the most rapid homogeneous water reduction catalysts, with a TOF of 654 mol of hydrogen per mole of catalyst per hour at an overpotential of 789 mV vs SHE (pH 7.0). Sustained water reduction catalysis occurs at glassy carbon (GC) to give H 2 over a 32 h electrolysis period with 95% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

The reaction of 2-pyridylamino- N , N -bis(2-methylene-4,6-difluorophenol) (H 2 L′) and MoCl 5 affords a molybdenum(VI) complex [MoL′(O) 2 ] 1 , a new molecular electrocatalyst, which has been determined by X-ray crystallography. Electrochemical studies show that a molybdenum(IV) intermediate is responsible for the reductive proton to generate H 2 , and 1 can catalyze hydrogen evolution from acetic acid or aqueous buffer. Turnover frequency (TOF) reaches a maximum of 50.6 (in DMF) and 756 (in buffer, pH 6.0) moles of hydrogen per mole of catalyst per hour, respectively. Sustained proton reduction catalysis occurs at glassy carbon (GC) electrode to give H 2 over a 72 h electrolysis period and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

The sluggish oxygen evolution reaction (OER) is considered as a major bottleneck for water splitting. It is critical to search for high performance of OER catalysts with different chemical compositions and structures. Herein, we report a new CoFe selenite with NH 4 + cation, further, an amorphous N -doped CoFe selenite can be obtained by an environmentally friendly in situ -method, further, by adjusting the ratio of Co and Fe and calcination temperature, the optimal electrocatalyst shows the lowest overpotential of 242 mV at 10 mA cm−2 on glassy carbon and a small Tafel slope of 59.1 mV dec−1, respectively, besides, this catalyst maintains the current density of 10 mA/cm2 for at least 24 h when applying overpotential of 242 mV. N -doping into this CoFe selenites can tailor its electronic structure, moreover, its mesoporous structure favors the mass transfer, electrolyte diffusion and O 2 release, in addition, the electrochemical oxidation processes can provide more active sites due to the surface modification of this CoFe selenites, consequently, exhibiting superior OER performance. This study provides an effective strategy to explore highly active and durable electrocatalysts for water splitting. Image 1 • An amorphous N -doped CoFe selenite was prepared via a facile in-situ N -engineering. • The optimal N -doped bimetallic CoFe selenite shows superior OER performance. • N doped into this CoFe Selenite could tailor its electronic structure. • The present study provides a strategy to explore new efficient OER electrocatalysts. [ABSTRACT FROM AUTHOR]

The reaction of N,N′-bis(3-aminopropyl) oxamido ligand (oxpn) and Cu(OH) 2 affords a dinuclear copper(II) complex, Cu(oxpn)Cu(OH) 2 1 , a molecular electrocatalyst for both water reduction and oxidation. Water oxidation occurs at an overpotential of 0.289 V with a turnover frequency (TOF) of ∼6.7 s −1 . Water reduction occurs with a TOF of 1383 moles of hydrogen per mole of catalyst per hour at an overpotential of 0.689 V (pH 7.0). Sustained water reduction catalysis occurs at glassy carbon (GC) to give H 2 over a 72 h electrolysis period with 97.4% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

The reaction of 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile (H 2 L1) and CoCl 2 ·6H 2 O affords a mixed-valent dinuclear Co II –Co I complex [Co I L(py) 3 ][Co II L 2 ] 1 (L = 2-(2-hydroxybenzylideneimino)-butenedinitrile ion), a new molecular electrocatalyst, which has been determined by X-ray crystallography and XPS spectrum. Electrochemical studies indicate that the catalyst is the first Co II –Co I complex species, that is among the most rapid homogeneous water-reduction catalysts, with a turnover frequency (TOF) of 2387 mol of hydrogen per mole of catalyst per hour at an overpotential of 787 mV vs SHE (pH 7.0). Sustained proton reduction catalysis occurs at glassy carbon (GC) to give H 2 over a 46 h electrolysis period with 97% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

The reaction of 2-pyridylamino-N,N-bis(2-methylene-4-ethyl-6-tert-butylphenol) (H 2 L) and MoCl 5 gives a molybdenum(VI) complex [MoL(O) 2 ] 1 , a new molecular electrocatalyst, which has been determined by X-ray crystallography. Electrochemical studies show that complex 1 can catalyze hydrogen evolution from acetic acid or aqueous buffer. Turnover frequency (TOF) reaches a maximum of 68 (in N,N -Dimethylformamide (DMF)) and 356 (in buffer, pH 6.0) moles of hydrogen per mole of catalyst per hour, respectively. Sustained proton reduction catalysis occurs at glassy carbon (GC) electrode to give H 2 over a 69 h electrolysis period and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

Transition metal phosphates electrocatalysts are promising candidates either for oxygen evolution reaction (OER) or oxygen reduction reaction (ORR) in water splitting or metal-air batteries due to their low cost and high electrocatalytic activity, however, it is still a great challenge to discover bifunctional electrocatalysts with a high electrocatalytic performance for OER and ORR. In this work, using a facile self-template method, the optimal 2D amorphous N-doped CoFe-phosphate displays superior electrocatalytic performances toward both ORR and OER, which exhibits a lower overpotential of 313 mV at 10 mA cm−2 (E j=10) for OER and a high half-wave potential of 0.74 V(E 1/2) for ORR and a small potential gap ΔE (ΔE = E j=10 − E 1/2) of 0.80 V in 1.0 M KOH electrolyte. Furthermore, this bifunctional electrocatalyst was applied in Zn–air battery with a high power density (74.6 mW cm−2), specific capacity (750 mAhg Zn −1), and long-term stability (over 30 h at 10 mA cm−2). Our study provided a new synthetic strategy to design and fabricate new 2D heteroatom-doped electrocatalytic materials with mesoporous structured for energy conversion applications, above all, in rechargeable Zn–air battery. [Display omitted] • A 2D N-doped CoFe phosphate was prepared via a facile in-situ N-engineering. • The optimal electrocatalyst exhibits excellent OER and ORR activity in 1.0 M KOH. • The superior performance is ascribed to its amorphous structure and N-doping. • The present study develops new bifunctional electrocatalysts for zinc-air batteries. [ABSTRACT FROM AUTHOR]

The reaction of 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile (H 2 L) and CuCl 2 ·2H 2 O affords a copper(II) complex [CuL] 1 , a new molecular electrocatalyst, which has been determined by X-ray crystallography. Electrochemical studies indicate that the catalyst is the first mononuclear copper(II) species with a turnover frequency of 457 (pH 7.0) moles of hydrogen per mole of catalyst per hour at an overpotential of 817 mV vs SHE, which is higher than some reported molecular catalysts for electrochemical hydrogen production from neutral water. Sustained proton reduction catalysis occurs at glassy carbon (GC) to give H 2 over a 72 h electrolysis period with 91.5% Faradaic yield and no observable decomposition of the catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile (H2L) and Ni(CH3CO2)2·2H2O affords a nickel(II) complex [NiL] 1, a new molecular electrocatalyst, which has been determined by X-ray crystallography. Electrochemical studies show that complex 1 can catalyze hydrogen evolution from acetic acid or from water. Turnover frequency (TOF) reaches a maximum of 193 (in DMF) and 574 (in buffer, pH 6) moles of hydrogen per mole of catalyst per hour, respectively. Sustained proton reduction catalysis occurs at glassy carbon (GC) electrode to give H2 over a 42 h electrolysis period and no observable decomposition of the catalyst. [Copyright &y& Elsevier]