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Designing high-performance electrocatalysts toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to reduce the activation barrier and optimize free adsorption energy of reactive intermediates. Herein, we report that incorporating high-valence Cr into NiSe2 (CrxNi1−xSe2) kinetically and thermodynamically expedites elementary steps of both HER and OER. The as-prepared Cr0.05Ni0.95Se2 catalyst displays excellent HER and OER activities, with low overpotentials of 89 and 272 mV at the current density of 10 mA·cm−2 (j10), respectively, and remains stable during operation for 30 h. A low cell voltage of only 1.59 V is required to drive j10 in alkaline media. In situ Raman spectroscopy reveals that Cr incorporation facilitates the formation of NiOOH active species during the OER process. Meanwhile, theoretical explorations demonstrate that high-valence Cr incorporation efficiently accelerates water dissociation kinetics and improves H* adsorption during HER process, lowering the activation barrier of OER and optimizing the adsorption energy of oxygen-based intermediate, thus kinetically and thermodynamically enhancing the intrinsic performance of NiSe2 for over water splitting. This strategy provides a new horizon to design transition metal based electrocatalysts in the clean energy field. [ABSTRACT FROM AUTHOR]

Seeking new cathode chemistry with high onset potential and compatibility with electrolytes has become a challenge for aqueous Zn ion batteries. Anion intercalation in graphite (4.5 V vs Li+/Li) possesses the potentiality but usually shows a competitive relationship with oxygen evolution reaction (OER) in aqueous solutions. Herein, a decoupled design is proposed to optimize a full utilization of perchlorate ion intercalation in graphite cathode by pH adjustment. Benefiting from the decoupled design, high Coulombic efficiency is obtained by decelerating the kinetic of OER in acidic media. The decoupled Zn‐graphite battery exhibits a wide potential window of 2.01 V, as well as an attractive energy density of 231 Wh kg−1. In addition, a Zn‐graphite battery with SO42−${\mathrm{SO}}_4^{2 - }$ insertion is assembled, which demonstrates the capability of the proposed decoupled strategy to integrate novel electrode chemistries for high‐performance aqueous Zn‐based energy storage systems. [ABSTRACT FROM AUTHOR]

The electrochemical decomposition of water plays a critical role in green and sustainable energy. However, the development of efficient and low-cost non-noble metal catalysts to overcome the high potential of the anodic oxygen evolution reaction (OER) is still challenging. In this work, electrocatalysts with high OER activity were obtained by doping Co/Fe bimetals into Ni3S2 (CF-NS) via a simple single-step hydrothermal method by adjusting the doping ratio of bimetals. A series of characterization studies revealed that the introduction of a Co/Fe co-dopant increased the number of active sites and improved the electroconductibility, while optimizing the electronic structure of Ni3S2. Meanwhile, Fe-induced high valence Ni contributed to the production of an OER active phase NiOOH. The unique dendritic crystal morphology facilitated the disclosure of the active sites and the expansion of mass transfer channels. The optimized sample required a low overpotential of 146 mV to obtain a current density of 10 mA cm−2 in 1.0 M KOH solution. The optimized sample also operated stably for at least 86 h. In sum, the proposed method looks very promising for designing efficient, stable, and low-cost non-precious metal catalysts with high conductivity and multiple active sites, useful for future synthesis of transition metal sulfide catalysts. [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]

Constructing earth‐abundant water splitting electrocatalysts performing platinum‐like activity is promising for the hydrogen economy but still a challenging task. Herein, the ultrafine CoMnP nanocrystals confined in amorphous carbon nanosheets are designed and implemented by a topological transformation strategy from layer double hydroxide/carbon interconnected structures in one single nanosheet. The unique interconnected structure favors the exposure of active sites and enables stronger electronic coupling effect between the two phases. Experimental results and density functional theory simulations reveal that the surrounding amorphous carbon and Mn dopants synergistically enable better electron delocalization capacity of Co sites, potentially providing enhanced conductivity and optimal reaction energetics during hydrogen evolution. The as‐prepared catalyst exhibits hydrogen evolution reaction performances superior to that of Pt/C under alkaline media with an overpotential of 114 mV at 100 mA cm–2. This work highlights the rational fabrication of transition metal‐based electrocatalysts via spatially confined growth for efficient water electrolysis. [ABSTRACT FROM AUTHOR]

The devise and fabrication of highly efficient electrocatalysts have momentous practical significance for the development of future hydrogen energy systems. However, their potential uses in support construction are not well studied. In this work, a highly efficient electrocatalyst is developed for the hydrogen evolution reaction by anchoring single Pt atoms and clusters into functional amorphous pentlandite Fe5Ni4S8 (or FNS) to yield Pt–FNS composites. Amorphous FNS still provides great conductivity to the composites, thereby promoting rapid charge transfer. The presence of abundant defects in Pt–FNS composite catalysts induces pleasant atomic dispersion and anchoring of Pt species. In addition, the formation of single Pt atoms combined with clusters and low‐Pt‐loading improves the utilization of Pt and reduces the cost. The turnover frequency analysis suggests Pt–FNS systems possess significant unit catalytic activity. The synergetic catalytic effect issued from high conductivity, abundant active sites and elevated intrinsic activity forms Pt–FNS systems with efficient pH‐universal catalytic activity. The systems exhibit low overpotentials of only 30, 65, and 98 mV at 10 mA cm−2 under acidic, alkaline, and neutral conditions, respectively. In sum, the proposed route looks promising for the fabrication of new electrocatalysts with improved properties. [ABSTRACT FROM AUTHOR]

Successful atom-by-atom controlling over surface and subsurface termination in a series of Fe−Pt intermetallic catalysts, via regulating the order degree of Fe/Pt, enables finely tuning their hydrogen evolution performance and thereof harvesting the superior hydrogen production with merits of a unique Fe/Pt coordination and oxidation-resistant Pt-rich surface. [Display omitted] Controlling the atomic arrangement of elemental atoms in intermetallic catalysts to govern their surface and subsurface properties is a crucial but challenging endeavor in electrocatalytic reactions. In hydrogen evolution reaction (HER), adjusting the d-band center of the conventional noble-metallic Pt by introducing Fe enables the optimization of catalytic performance. However, a notable gap exists in research on the effective transition from disordered Fe/Pt alloys to highly ordered intermetallic compounds (IMCs) such as FePt 3 in the alkaline HER, hampering their broader application. In this study, a series of catalysts FePt 3 - x H (x = 5, 6, 7, 8 and 9) supported on carbon nanotubes (CNTs) were synthesized via a simple impregnation method, along with a range of heat treatment processes, including annealing in a reductive atmosphere, to regulate the order degree of the arrangement of Fe/Pt atoms within the FePt 3 catalyst. By using advanced microscopy and spectroscopy techniques, we systematically explored the impact of the order degree of FePt 3 in the HER. The as-prepared FePt 3 -8H exhibited notable HER catalytic activity with low overpotentials (η = 37 mV in 1.0 mol L−1 KOH) at j = 10 mA cm−2. The surface of the L1 2 FePt 3 -8H catalyst was demonstrated to be Pt-rich. The Pt on the surface was not easily oxidized due to the unique Fe/Pt coordination, resulting in significant enhancement of HER performance. [ABSTRACT FROM AUTHOR]

The development of low-price and highly efficient catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has always been challenging with regard to water splitting. Pyrrhotite Fe 7 S 8 has become a research hotspot due to its abundant reserves, high electrical conductivity and excellent catalytic activity. In general, introducing metal heteroatoms into transition metal sulfides (TMSs) can effectively enhance the activity and stability of TMSs. Herein, Co-doped pyrrhotite Fe 7 S 8 nanosheets were obtained by a straightforward two-step method consisting of hydrothermal treatment followed by subsequent heat treatment. Results from XPS analysis and contact angle measurements showed that doping optimized the chemical environment around iron atoms and enhanced the adsorption of water molecules on the surface of Fe 7 S 8 , thereby greatly improving the electrocatalytic efficiency of water electrolysis. Compared with other counterparts, Co 0 · 95 Fe 6 · 05 S 8 exhibited superior OER activity with an overpotential of 311 mV at a current density of 10 mA cm−2, and higher performance towards HER with an overpotential of 284 mV at 10 mA cm−2 in alkaline solution. In sum, Co 0 · 95 Fe 6 · 05 S 8 is promising as a bifunctional catalyst for water splitting under alkaline conditions. [ABSTRACT FROM AUTHOR]

Fe 5 Ni 4 S 8 /Ni 3 S 2 is a highly efficient and robust bifunctional electrocatalyst for overall water splitting due to its charge transport double-channel structure and strong electronic interaction. [Display omitted] • The stepped rod-shaped Ni 3 S 2 3D nanoarray structure supplied the system with sufficient active sites. • The double-channel structure, which consisted of high-conductivity Fe 5 Ni 4 S 8 and NF, provided an increase in the rate of internal charge transfer. • The overall water splitting device with appropriate samples achieved 1.64 V@10 mA cm−2 cell voltage. And it remained active for at least 120 h at an industrial-grade high current density (500 mA cm−2). Overall water splitting technology is critical for the future of a clean and sustainable hydrogen energy infrastructure. Ni 3 S 2 (NS) is considered a good performing oxygen evolution reaction (OER) catalyst, but exhibits unsatisfactory hydrogen evolution reaction (HER) activity. In this study, Fe 5 Ni 4 S 8 (FNS) material was incorporated into an NS nanoarray, generating a low-cost, efficient, and stable bifunctional FNS/NS heterostructure for electrolyzed water catalysts. The hydrophilicity of pretreated FNS was quite high, whereas the stepped rod-shaped NS structure had a large number of radial active sites. Additionally, the high-conductivity of FNS and nickel foam (NF) provided a double-channel structure for rapid internal charge transfer. The interconnecting a network of FNS, rod-shaped NS nanoarray, and NF substrate enabled one to accomplish a synergistic effect of enhanced kinetics and activity of OER, HER, and overall water splitting. To achieve a current density of 10 mA cm−2 in 1.0 M KOH solution, only overpotentials of 248 and 94 mV were required. Moreover, the voltage of the constructed FNS/NS||FNS/NS double-electrode battery system was only 1.64 V@10 mA cm−2, but the battery could have run for at least 120 h at an industrial current density of 500 mA cm−2. Therefore, this study offers a rational design of heterostructures as bifunctional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]