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Enhancing catalytic activity through modulating the interaction between N-doped carbon and metal phosphides clusters is an effective approach. Herein, the electronic structure modulation of CoP2 supported N-modified carbon (CoP2/NC) has been designed and prepared as efficient electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Notably, CoP2/NC-1 catalyst exhibits impressive performance in alkaline media, with an ORR half-wave potential of 0.84 V, as well as OER and HER overpotentials of 290 and 129 mV (at 10 mA·cm−2), respectively. In addition, CoP2/NC-1 produces a power density as high as 172.9 mW·cm−2, and excellent reversibility of 100 h at 20 mA·cm−2 in home-made Zn-air batteries. The experimental results demonstrate that the synergistic interactions between N modified carbon substrate and CoP2 material significantly enhance the kinetics of ORR, OER, and HER. Density functional theory (DFT) calculations reveal the strong electrons redistribution of CoP2 induced by high-density N atoms at the interface, thus optimizing the key intermediates and significantly lower the energy barrier of reactions. These electronic adjustments of CoP2 greatly enhance its kinetics of ORR/OER/HER, leading to faster reactions. This study provides profound insights into the specific modification of CoP2 by N-doped carbon, enabling the construction of efficient catalysts. [ABSTRACT FROM AUTHOR]

The p-n heterojunction Co 3 O 4 /RuO 2 anchored on carbon matrix (Co 3 O 4 /RuO 2 -C) is constructed for acidic water oxidation, wherein the electron could diffuse from RuO 2 to Co 3 O 4 to pre-modify electronic structure of RuO 2 , facilitating redox of Ru sites and dominating adsorbate evolution mechanism of oxygen evolution to endow Co 3 O 4 /RuO 2 -C with excellent activity in water oxidation without trade-off stability. [Display omitted] • A p-n heterojunction of Co 3 O 4 /RuO 2 anchored on carbon matrix is facilely developed for improved acidic oxygen evolution reaction. • The experimental and theoretical results indicate electron flow could occur from RuO 2 to Co 3 O 4 , achieving pre-modifying electronic structure of RuO 2. • In situ total reflection infrared (ATR-IR) can validate adsorbate evolution mechanism of oxygen generation for heterojunction of Co 3 O 4 /RuO 2. • In situ Raman test suggest facile evolution of Ru active sites after formation of p-n heterojunction of Co 3 O 4 /RuO 2. Development of Ru-based electrocatalysts for acidic oxygen evolution reaction without a trade-off between activity and durability remains challenging. Herein, we constructed Co 3 O 4 /RuO 2 heterojunctions anchored on carbon (Co 3 O 4 /RuO 2 -C) with a low Ru loading (2.74 wt%), in which strong coupled p-n junctions facilitated electron transfer from RuO 2 to Co 3 O 4. The Co 3 O 4 /RuO 2 -C demonstrated a low overpotential of 170 mV at 10 mA cm−2 and long-term stability in 0.1 M HClO 4 due to its unique structure. The origin of its high performance in acidic OER was revealed by the combination of in-situ attenuated total reflection infrared and Raman tests. Concretely, oxygen generation for Co 3 O 4 /RuO 2 -C was dominated by the adsorbate evolution mechanism, and the introduction of Co 3 O 4 facilitated the redox of RuO 2 , generating active sites for OER. Theoretical calculations further substantiated that the Co 3 O 4 /RuO 2 heterojunctions possessed lower energy barriers for OER. This work provides a compelling synthesis route for effective and stable electrocatalysts for acidic OER. [ABSTRACT FROM AUTHOR]

Inspired by the excellent activity of platinum in hydrogen evolution reaction (HER) and the good performance of Ni-based compounds in oxygen evolution reaction (OER), a bifunctional electrocatalyst PtNi carbon nanofiber (CNF) is designed and fabricated using electrospinning followed by carbonization. Ultra-small PtNi nanoparticles of several nanometers in size are densely dispersed on every CNF, along with a few larger nanoparticles with sizes of several decades of nanometers. The as-prepared catalysts can be directly used as an electrode and act as high-efficiency materials for water splitting, including HER and OER. For HER activity, the PtNi/CNFs reach 10 mA cm current density at low overpotentials of 34 mV and exhibit a small Tafel slope of 31 mV dec in acidic electrolytes of 0.5 M HSO, which is close to that of commercial Pt/C (20 wt%) electrocatalytic catalysts. In 1 M KOH solution, the PtNi/CNFs also exhibit excellent HER activity with a low overpotential of 82 mV to achieve a current density of 10 mA cm and a small Tafel slope of 34 mV dec. Moreover, the PtNi/CNFs also show good activity for OER in alkaline electrolyte of 1 M KOH with a Tafel slope of 159 mV dec and a small overpotential of 151 mV to reach a current density of 10 mA cm. In addition, the OER performance of the PtNi/CNFs in acid media is also favorable, with a 198 mV dec Tafel slope. The decent activity of the PtNi/CNFs for water splitting originates from the synergistic effects of using Pt and Ni, large amounts of ultra-small nanoparticles densely dispersed on the CNFs, high conductivity of the support materials and interconnected three-dimensional structures of the carbon nanofiber mats. [ABSTRACT FROM AUTHOR]

Efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be developed to realize an inexpensive water-splitting system for large-scale applications. Herein, a novel PdNi carbon nanofiber (PdNi/CNF) catalyst was synthesized by facile electrospinning and carbonization processes. The size and homogeneity of the Pd−Ni alloy nanoparticles (NPs) could be effectively tuned by controlling the molar feed ratio of metal precursors .The morphology and structure of the PdNi/CNFs were characterized, and the working electrodes fabricated from the prepared catalyst mats were directly employed in the HER and OER. The PdNi/CNFs-1:2 catalyst exhibits high catalytic activity in the HER with a low overpotential of 55 mV at a current density of 10 mA cm −2 in an acidic solution. Moreover, under 1 M KOH electrolyte, an overpotential of 187 mV is required in the HER over the catalyst to arrive 10 mA cm −2 and an overpotential of 289 mV is achieved in the OER at the same current density. The superior HER and OER activities of the PdNi/CNFs are attributed to the synergistic effects of the PdNi alloy nanoparticles (NPs) assembled on the CNFs. This work provides a simple route for synthesizing highly efficient bifunctional electrocatalysts from 3d transition metals and a small amount of noble metals for hydrogen and oxygen evolution reactions. [ABSTRACT FROM AUTHOR]

Fe incorporated Ni-based electrocatalysts have emerged as one of the most active oxygen-evolving catalysts under alkaline conditions and deciphering the effect of iron incorporation in enhancing the activity is challenging but critical for the catalyst design. Herein, the as-prepared nanocube Ni-based catalysts underwent a reconstruction process and transformed from γ-NiOOH to β-NiOOH structure by iron incorporation under the applied bias, which was confirmed by in-situ Raman measurement. According to the methanol oxidation current response difference, the hydroxyl adsorption intensity was proposed to be regulated by iron incorporation and the rate-determining step would be the formation of *OOH for Fe-doped β-NiOOH, which was further supported by DFT calculation. This work reveals the effect of iron-doped on the phase structure transform and the regulation of intermediate species elaborately and offers new insight on the understanding of the activity origins for NiFe-based catalysts. [Display omitted] • Potential-induced reconstruction process from γ-NiOOH to β-NiOOH structure by iron incorporation under applied bias. • The Fe-doped β-NiOOH exhibited an overpotential of 247 mV at 10 mA·cm−2 and a Tafel slope of 40.15 mV·dec−1. • The surface coverage of *OH varies in the trend: NiOOH > Fe-doped β-NiOOH > FeOOH. [ABSTRACT FROM AUTHOR]

Delicate construction of sophisticated bimetallic nanostructures provides a favorable way to boost the efficiency of bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is critical to the fabrication of rechargeable Zn-air batteries. Herein, hetero-structured Cu/Co 93 Cu 7 nanoparticles confined inside N-doped carbon nanocages (denoted as Cu/Co 93 Cu 7 @NC NCs) are fabricated through a facile "MOF-in situ-reduction and in situ-growth-MOF" strategy. Benefiting from the unique hollow architecture and superior intrinsic activity of the optimized interfaces, the as-prepared catalyst displays an appealing electrocatalytic performance including a positive half-wave potential (E 1/2) of 0.88 V for ORR and a low OER overpotential of 262 mV at 10 mA cm−2. Theoretical calculations further disclose the key role of the rationally designed Co/Cu/N-doped carbon heterostructures, which significantly reduces the energy barrier for *OOH formation and eventually promotes the ORR. Rechargeable Zn-air batteries assembled with the Cu/Co 93 Cu 7 @NC NCs exhibit a large specific capacity of 884.9 mAh g Zn −1 and a maximum power density of 225.9 mW cm−2. Moreover, the assembled batteries are stable for 1000 h during the long-term charge and discharge cycling, demonstrating the great promise for practical applications. [Display omitted] • An efficient Cu/Co 93 Cu 7 @NC NCs catalyst is designed for ORR and OER. • The hollow architecture enhances the electrocatalytic kinetics. • DFT verifies that N–C, Cu and Co cooperatively improve the intrinsic activity. • The as-assembled Zn-air batteries exhibit excellent activity and durability. [ABSTRACT FROM AUTHOR]

A bifunctional Co 2 (OH) 3 Cl/FeOOH electrode used in a 10*10 cm2 membrane electrode assembly for a cyclohexanone production rate of 3.44 g/h and electricity saved about 0.24 kWh/m3 (H 2). The carbon free-radical reaction pathways for cyclohexanol electrooxidation on CoII/CoIII redox active species was elaborately elucidated. [Display omitted] • A voltage of 1.46 V at 10 mA·cm−2 was required for H 2 and CXO product. • In-situ measurements and DFT calculations elucidated the synergistic effect. • Carbon free-radical pathway for CXL oxidation on CoII/CoIII redox active species. • A CXO yield was 3.44 g/h and electricity saved about 0.24 kWh/ m3 (H 2) in MEA. Replacing oxygen evolution reaction with the more thermodynamically favorable organics oxidation reaction is crucial to reduce the required voltage of overall water splitting. Herein, Co 2 (OH) 3 Cl/FeOOH nanosheets are served as both cathode and anode for the concurrent high purity hydrogen generation and high value-added cyclohexanone productions. Thanks to the wondrous synergistic effect between Co 2 (OH) 3 Cl and FeOOH, for Co 2 (OH) 3 Cl acted as the optimal catalytic sites for cyclohexanol oxidization and FeOOH accelerated the reaction rates by reducing the charge transfer resistance, the two-electrode configuration only required a voltage as low as 1.46 V at 10 mA·cm−2 for cathode H 2 and anode cyclohexanone. Moreover, by further scaling up the configuration into the 10*10 cm2 anion membrane electrode assembly reactor, a cyclohexanone production rate of 3.44 g/h and the electricity saved about 0.24 kWh/ m3 (H 2) were achieved. In addition, the reaction pathways, the C–H bond cleaves first, and then the intermediate carbon free radical is dehydrogenated to generate cyclohexanone on CoII/CoIII redox, was elucidated elaborately. This work offers an approach to actuate effective transformation of organics with high selectivity and industrial practicability under ambient conditions powered by renewable energy. [ABSTRACT FROM AUTHOR]

Promoting the self-reconstruction of NiFe-based catalysts represents a promising approach to facilitate seawater splitting, albeit with significant challenges. Herein, the redox cycle of Ni species is subtly regulated by decorating NiFe hydroxides with vanadium. Both experimental and theoretical studies demonstrate that the incorporation of V boosts the self-reconstruction of NiFe hydroxides and allows a superior OER performance on account of diminished propensity for chlorine adsorption and optimized binding energy of oxygen-containing intermediates. Consequently, the NiFeV/NF catalyst delivers 2.0 A cm−2 at an ultralow overpotential of 369 mV in 1.0 M KOH and exhibits exceptional stability for 720 h at 20 A in an alkaline membrane electrode assembly (MEA) electrolyzer. In alkaline seawater, it achieves prolonged stability, surpassing 240 h at 500 mA cm−2 with OER selectivity of 99 %. This work significantly advances the field of seawater electrolysis powered by marine renewables, paving the way for on-site hydrogen production. [Display omitted] • The redox cycle of Ni species is subtly regulated by decorating NiFe hydroxides with vanadium. • The incorporation of V diminishes the propensity of Cl− adsorption and optimizes the absorption of oxygen-containing species. • The NiFeV/NF delivers 2.0 A cm−2 at an overpotential of 369 mV and exhibits exceptional stability for 720 h at 20 A. • Deciphering the contributions of Cl* and OH* to the activity of seawater oxidation. [ABSTRACT FROM AUTHOR]

Achieving large current density is crucial to the practical application of large-scale hydrogen production by water splitting, but it is hindered by sluggish and unstable catalysts. Herein, a Pt-induced NiFe layered double hydroxide (Pt-NiFe LDH) nanosheet is synthesized for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It affords 10 mA cm–2 at overpotentials of only 198 mV and 36 mV for OER and HER, respectively. Impressively, an alkali-electrolyzer (Pt-NiFe LDH || Pt-NiFe LDH) exhibits a stable cell voltage of 1.887 V to deliver a current density of 1000 mA cm–2 over 3000 h. The introduction of Pt modulates the electronic structure on the surface of NiFe LDH by charging redistribution at the interface and decreasing the Gibbs free energy change (ΔG) for the potential determining step (from *O to *OOH) during OER. This work provides a facile strategy for developing catalysts for large current density water splitting. [Display omitted] • The Pt-NiFe LDH obtains excellent HER/OER activity in alkaline medium. • The homemade alkaline electrolyzer operated at 1000 mA cm−2 for over 3000 h. • The density functional theory (DFT) reveals that the introduction of Pt clusters on NiFe LDH reduces the energy barrier of OER. [ABSTRACT FROM AUTHOR]