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Utilizing dual ligand environment to construct porous hollow structure of Prussian blue analogues (PBAs). Amorphous-crystalline CoP with plentiful exposed (1 1 1) crystal plane which induced by low-valence cobalt chelated by EDTA can boost the activity in hydrogen evolution after phosphating. [Display omitted] • Electronic structure of CoP can be regulated using dual ligand environment for HER. • Amorphous-crystalline and hollow porous CoP with lower valence cobalt is prepared. • The microwave heating and phosphating process contribute to the formation of CoP. • The optimal ratio of EDTA to Co3+ and different precursor states are explored. CoP is one of the most promising catalysts for catalyzing hydrogen evolution reaction. The foremost issue is how to improve intrinsic activity by regulating electronic structure at the molecular level. Herein, utilizing selective combination of EDTA and Co2+, an amorphous-crystalline CoP with lower valence cobalt and hollow porous structure which induced by dual ligand environment is successfully synthesized via microwave heating and following phosphating process. Synthesize CoPBA from EDTA3+ and Co3+ in a ratio of 1:1 and followed by phosphating (ECP-1) exhibits excellent performance for HER in alkaline media, requiring 173 mV to achieve 10 mA cm−2. The enhanced catalytic activity may be ascribed to the amorphous-crystalline crystal structure with enlarged exposure of active sites and the hollow porous framework induced by EDTA, as well as the homogeneously distribution of (1 1 1) plane, on which the change of free energy on both Co bridge sites and P top sites is close to zero when adsorbing hydrogen. Besides, its great catalytic stability has been evaluated via 1000 cycles of CV measurement. The possible mechanism of valence state regulation of cobalt ions in CoP is discussed in detail. Furthermore, the optimal ratio of EDTA to Co2+ and different precursor states are explored reasonably. [ABSTRACT FROM AUTHOR]

High-valence metals such as Mo, W, etc. can modulate the adsorption and desorption energy of 3 d -metal-based electrocatalysts, favorable for the intrinsic activity for hydrogen evolution reaction (HER) at large current density. However, the facile and exact incorporation of high-valence metals remains a big challenge. Herein, a metallic MoO x layer has been designed via anodization of Mo foil to achieve high-valence Mo doping into CoP to finally form the real active component Mo-CoP for HER. The activated metallic MoO x layer provides an optimized Mo doping into CoP, obtaining Mo-CoP/MoO x with ~226 mV (alkaline) and ~275 mV (acidic) at > 2000 mA cm-2. Meanwhile, in-situ grown F-Mo-CoP/MoO x controllable treated by fluoroaniline possesses enhanced the structural robustness of Mo-CoP/MoO x with long-term stability at large current density. This work not only illustrates the facile approach of regulating electron structure via high-valence metal doping, but it also provides the rational strategy for enhanced stability for industrial applications. [Display omitted] • A metallic MoO x layer has been designed via anodization of Mo foil. • MoO x layer is helpful to achieve high-valence Mo doping into CoP for enhanced HER. • Mo-CoP/MoO x has the overpotential of ~226 mV (alkaline) and ~275 mV (acidic) at > 2000 mA cm-2. • F-Mo-CoP/MoO x controllable treated by fluoroaniline has the long-term stability at large current density. [ABSTRACT FROM AUTHOR]

Ultrafine and high-density RuP 2 based on coordination chemistry and catalyst-support correlation shows potential for hydrogen evolution reaction (HER). Herein, the uniform and high-density W-doped ultra-small RuP 2 (W 0.05 -RuP 2 @C 3 N 4 -NC) are synthesized by incorporating oxygen-bridged [WO 4 ] tetrahedron into tetraacetic acid (EDTA)-melamino-formaldehyde (MF) ligands. EDTA-MF shows strong metal-support interaction, dedicating to the optimal dispersion, highest Ru yields, and HER activity. W atoms regulate local electron structure and coordination environment, leading to faster proton supply and hydrogen release, thus achieving 10 mA cm−2 at low overpotential of 27 mV (alkaline) and 66 mV (acidic). Notably, W 0.05 -RuP 2 @C 3 N 4 -NC maintains stability with staged 500–1000 mA cm−2 for 1000 h in alkaline, and 1000 mA cm−2 for ~300 h in acid, ascribing to the immobilized ultra-stable RuP 2 nanoclusters via EDTA-MF and metal-oxygen sites. The excellent activity and stability hold promise for industrial hydrogen production, which provides deeper insights into catalyst-support interaction and reasonable design of high Ru-loading electrocatalysts. [Display omitted] • EDTA and MF provide coordination effect for the doping of W into RuP 2. • The strong metal-support interaction is helpful for the optimal dispersion, high loading of Ru. • W atoms regulate local electron structure and coordination environment. • W 0.05 -RuP 2 @C 3 N 4 -NC shows activity and stability for HER in acid and alkaline solution. [ABSTRACT FROM AUTHOR]

A 30 s hydrolysis reaction is used to rapidly synthesize CoFeOH encapsulated CoFeP on iron foam (CoFeOH/CoFeP/IF) with amorphous-crystalline interface and double catalytic sites. Where the loss of phosphorus is inhibited (near 60%) and CoFeOH/CoFeP/IF shows higher hydrogen evolution reaction (HER) property in alkaline media. When drives 100, 500, 1000, 2000 and 3000 mA cm−2, it only requires overpotentials of 114.9, 194.9, 221.8, 249.7 and 266.1 mV in 1.0 M KOH (25 °C) with at least 100-h durability (500 and 1000 mA cm−2). Further simulated industrial tests indicate that the CoFeOH/CoFeP/IF has lower Tafel value and faster HER kinetics in 7.6 M KOH (70 °C). When coupling with NiFe-LDH/IF in a two-electrode system, the voltage of NiFe-LDH/IF (+) || CoFeOH/CoFeP/IF (−) at 2500 mA cm−2 is merely 1.57 V (7.6 M KOH 70 °C). Even in 1.0 M KOH (25 °C) solution, it only needs 1.88 V. This work may provide the guidance for constructing catalytic interface to enhance the HER performances. [Display omitted] • CoFeOH/CoFeP on iron foam (CoFeOH/CoFeP/IF) is rapidly prepared by 30 s hydrolysis. • CoFeOH/CoFeP/IF has amorphous-crystalline interface and double catalytic sites. • CoFeOH/CoFeP/IF shows the higher HER activity and stability at large current. • The rapid hydrolysis may be an effective way for high-current-density catalysts. [ABSTRACT FROM AUTHOR]

• The hydrogen evolution under large-current-density is tested for industrial electrolysis of water. • F doping may facilitate the intrinsic activity for HER at the large current density. • The fluorine-doped Co 2 P/Fe 2 P/IF shows the excellent activity for HER at large current density. • The iron foam as substrate may bear the high current density during industrial water electrolysis. Developing the transition metal-based electrocatalysts for hydrogen evolution reaction (HER) under large-current-density is crucial for industrial electrolysis of water. However, most of reported HER electrocatalysts in alkaline solution are tested under the current density of less than 100 mA cm−2. In this work, CoFe Prussian blue analogues (PBA) supported on iron foam (IF) as precursor can (has been) be utilized to construct the fluorine-doped cobalt-iron phosphides (F-Co 2 P/Fe 2 P/IF). At the large-current-density at 100, 500, 1000 and 2000 mA cm−2, we systematically investigate the HER performance of F-Co 2 P/Fe 2 P/IF. Compared to the electrocatalyst without F− doping, F-Co 2 P/Fe 2 P/IF only need the low overpotential of 229.8, 260.5, 292.2 and 304.4 mV, respectively, when reaching the large current of 500, 1000, 2000 and 3000 mA cm−2. The F doping may induce the valence state and electronic structure of Co and Fe ions for enhanced HER activity. The role of F doping is furtherly analyzed by introducing barium ions as precipitation agent. At the same time, it can maintain for a long-term stability in 1.0 and 6.0 M KOH at the different high current density. The stableF-Co 2 P/Fe 2 P/IF may bear the high current density and high temperature during industrial water electrolysis. This work enables it possible at the large current density for industrial water splitting. [ABSTRACT FROM AUTHOR]