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The advancement of a naturally rich and effective bifunctional substance for hydrogen and oxygen evolution reaction is crucial to enhance hydrogen fuel production efficiency via the electrolysis process. Herein, facile and scalable hydrothermal synthesis of bifunctional electrocatalyst of polyoxometalate anchored zinc cobalt sulfide nanowire on Ni‐foam (NF) for overall water splitting is reported for the first time. The electrochemical analysis of POM@ZnCoS/NF displays significantly low HER and OER overpotentials of 170/337 and 200/300 mV to attain a current density of 10/40 and 20/50 mA cm−2, respectively, demonstrating the notable performance of POM@ZnCoS/NF toward H2 and O2 evolution reaction in alkaline medium. Additionally, the electrolyzer consisting of the POM@ZnCoS/NF anode and cathode shows an appealing potential of 1.56 V to deliver 10 mA cm−2 current density for overall water splitting. The high electrocatalytic activity of the POM@ZnCoS/NF is attributed to modulation of the electronic and chemical properties, increment of the electroactive sites and electrochemically active surface area of the zinc cobalt sulfide nanowires due to the anchorage of polyoxometalate nanoparticles. These results demonstrate the advantage of the polyoxometalate incorporation strategy for the design of cost‐effective and highly competent bifunctional catalysts for complete water splitting. [ABSTRACT FROM AUTHOR]

Abstract: An efficient, durable, and low‐cost hydrogen evolution reaction (HER) catalyst is an essential requirement for practical hydrogen production. Herein, an effective approach to facilitate the HER kinetics of molybdenum carbide (Mo2C) electrocatalysts is presented by tuning its electronic structure through atomic engineering of nitrogen implantation. Starting from the organoimido‐derivatized polyoxometalate nanoclusters with inherent MoN bonds, the formation of N‐implanted Mo2C (N@Mo2C) nanocrystals with perfectly adjustable amounts of N atoms is demonstrated. The optimized N@Mo2C electrocatalyst exhibits remarkable HER performance and good stability over 20 h in both acid and basic electrolytes. Further density functional theory calculations show that engineering suitable nitrogen atoms into Mo2C can regulate its electronic structure well and decrease MoH strength, leading to a great enhancement of the HER activity. It could be believed that this ligand‐controlled atomic engineering strategy might influence the overall catalyst design strategy for engineering the activation sites of nonprecious metal catalysts for energy conversions. [ABSTRACT FROM AUTHOR]

[Display omitted] • POM-ZnFe 2 O 4 hybrid is reported first time for overall water splitting. • POM-ZnFe 2 O 4 hybrid delivers extraordinary performance for OER and HER. • The high structural integrity and ultralong durability is maintained by the hybrid. Electrocatalysts play an important role to increase the energy conversion efficiency of electrolysis processes. In this study, a heterostructure of zinc iron oxide (ZnFe 2 O 4) and polyoxometalate (POM) nanoplates (POM–ZnFe 2 O 4) was fabricated for the first time by a hydrothermal process. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) analysis of POM–ZnFe 2 O 4 furnished low overpotentials of 268 and 356 mV, and 220 and 290 mV to achieve current densities of 20 and 50 mA cm−2, respectively. In addition, an electrolytic cell composed of a POM–ZnFe 2 O 4 cathode and anode required an operating voltage of 1.53 V to deliver a current of 10 mA cm−2. The improved electrochemical performance of POM–ZnFe 2 O 4 compared to commercial and recently reported catalysts is attributed to the high electrocatalytically active surface area, modulation in the electronic and chemical properties and the formation of heterojunction of ZnFe 2 O 4 and POM, which are vital for accelerating HER and OER activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel 3D nano-assembly of NiCo 2 S 4 /PANI@PW 12 /rGO hybrid is reported first time. • NiCo 2 S 4 /PANI@PW 12 /rGO hybrid delivers extraordinary performance for LIB and HER. • The high structural integrity and ultralong durability is maintained by the hybrid. Engineering hierarchical nanostructures with enhanced charge storage capacity and electrochemical activity are vital for the advancement of energy devices. Herein, a highly ordered mesoporous three-dimensional (3D) nano-assembly of Nickel Cobalt Sulphide/Polyaniline @Polyoxometalate/Reduced Graphene Oxide (NiCo 2 S 4 /PANI@POM/rGO) is prepared first time via a simple route of oxidative polymerization followed by a hydrothermal method. Morphological analysis of the resulting hybrid reveals the sheet-like structures containing a homogeneous assembly of PANI@POM and NiCo 2 S 4 on the graphene exterior maintaining huge structural integrity, large surface area and electrochemically active centres. The electrochemical analysis of the nanohybrid as the anode of the lithium-ion battery (LIB) has delivered ultra-huge reversible capacity of 735.5 mA h g−1 (0.1 A g−1 after 200 cycles), superb capacity retention (0.161% decay/per cycle at 0.5 A g−1 for 1000 cycles), and significant rate capability (355.6 mA h g−1 at 2 A g−1). The hydrogen evolution reaction (HER) measurement also proves remarkable activity, extremely low overpotential and high durability. The extraordinary performance of the nanohybrid is due to the presence of abundant electroactive centres, high surface area and a large number of ion exchange channels. These outstanding results prove the advantages of a combination of NiCo 2 S 4 , graphene sheets, and PANI@POM in energy devices. [ABSTRACT FROM AUTHOR]

Highlights • Cu dendrites exclusively induced by Anderson type POM (NH 4) 4 [H 6 NiMo 6 O 24 ]. • Chemical association between POMs and Cu NPs was evidenced via XPS and Raman investigation. • Enhanced HER activity with NiMo 6 O 24 @Cu/TNA was achieved. • Mechanism of NiMo 6 O 24 @Cu/TNA electrochemical HER was investigated by Tafel study. • NiMo 6 O 24 @Cu/TNA system shows high stability with enhanced corrosion resistance under neutral and acidic environment. Abstract The design and synthesis of specific functional complex materials as desired catalysts for improved energy conversion and storage are of great importance and with grand challenges. Here, a facile synthesis strategy of Anderson POMs supported Cu dendrites toward electrochemical hydrogen evolution reaction with dramatically decreased overpotential under acidic aqueous condition is established in this work. We present the preparation of well crystallized Cu dendrites through co-electrodeposition on TiO 2 array with Anderson-type POM NiMo 6 O 24. Structural and state of valence investigation of the as-obtained electrocatalyst (NiMo 6 O 24 @Cu/TNA) evidence the specific morphology tunability and modification of Cu dendrites surfaces. During HER course, NiMo 6 O 24 can improve the H+ transfer and further help the H atom absorption which remedies the weakness of insufficient H atom absorption ability of Cu along with its strong electron transfer lowering overpotential upon HER. Therefore, HER with NiMo 6 O 24 @Cu/TNA is considerably enhanced by decreasing related overpotential of 130 mV compared to porous Cu foam. The modification of NiMo 6 O 24 endowed catalysts strong corrosion resistance assuring long term stability. Hence, the proposed strategy possesses improved activity and long term stability upon HER with NiMo 6 O 24 @Cu/TNA as electrocatalyst. Depending on the diversity of POMs, the current feasible and reliable heterogeneous electrocatalysts design with POMs would inspire more effective, low-cost strategies for energy conversion and open the pathway for large scale production. [ABSTRACT FROM AUTHOR]

The design of a low-cost, highly efficient and durable electrocatalyst is very important to accelerate the energy conversion efficiency of the electrochemical process. Herein, a simple hydrothermal synthesis of the heterostructure of Wells-Dawson polyoxometalate and zinc iron layered double hydroxide nanosheet is presented for the first time on Ni-foam (ZnFe LDH-P 2 Mo 18 /NF). The electrocatalytic activity of ZnFe LDH-P 2 Mo 18 /NF shows significantly low overpotentials of 275, 330 mV and 273, 367 mV for OER and HER to acquire a current density of 20, 50 mA cm−2 respectively. Additionally, the electrolyzer composed of ZnFe LDH-P 2 Mo 18 /NF cathode and anode shows an attractive voltage of 1.54 V to carry 10 mA cm−2. The better electrochemical performance of the ZnFe LDH-P 2 Mo 18 /NF is ascribed to the variation of electronic and chemical features, growth of electrochemically active surface area/sites because of the construction of heterointerface of Wells-Dawson polyoxometalate and zinc iron LDH. These results further demonstrate the benefits of heterointerface engineering for efficient electrolysis. This study presents a novel hybrid of zinc-iron layered double hydroxide and Dawson polyoxometallate (ZnFe LDH-P 2 Mo 18 /NF) for electrocatalytic water splitting. Notably, ZnFe LDH-P 2 Mo 18 /NF reveals excellent electrocatalytic performance with a large number of electroactive sites, extremely low overpotential, and high durability throughout the water splitting process. [Display omitted] • ZnFe LDH-P 2 Mo 18 hybrid is reported first time for overall water splitting. • ZnFe LDH-P 2 Mo 18 hybrid delivers extraordinary performance for OER and HER. • The high structural integrity and ultralong durability is maintained by the hybrid. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent development of polyoxometalates for hydrogen evolution reaction is summarized. • Mechanisms and challenges of polyoxometalates for hydrogen evolution reaction is summarized. • Structural design, performances and functions of polyoxometalates for HER electrocatalysis is summarized. • Perspectives for future design of highly efficient and stable HER electrocatalysts are proposed. Electrocatalytic water splitting via hydrogen evolution reaction (HER) from renewable energy sources is an attractive alternative to produce hydrogen, but it still encounters the limitations of large-scale applicability of Pt-based electrocatalysts. Therefore, abundant efforts have been devoted to design and fabricate highly efficient and stable noble-metal-free electrocatalysts to replace the expensive Pt-based electrocatalysts. Recently, polyoxometalates (POMs) and their derivatives have been proven to provide plentiful opportunities for designing and fabricating highly efficient and stable noble-metal-free HER electrocatalysts with controllable catalytic active sites and well-defined nanostructures. In this review, recent advances on coordination structures and HER performances of POMs-contained composites and POMs-derived transition metal carbides, chalcogenides, phosphides, nitrides and other electrocatalysts have been discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The in-situ confined carbonization of PMo 12 @UiO-66 reduces aggregation and improves conductivity of MoC@PC. • Etching ZrO 2 realizes desired porous MoC@PC with ultra-high specific surface area of 1039 m2·g−1. • Confined phosphorization of MoC@PC gives raise to superhydrophilic MoP-QDs@PC. • The superhydrophilic MoP-QDs@PC exhibits excellent HER performance superior to commercial 20% Pt/C. Fabricating low-cost, earth-enriched and high-performance electrocatalysts for hydrogen evolution reaction (HER) is significant but challenging for the development of a sustainable hydrogen economy. Herein, we report superhydrophilic molybdenum phosphide quantum dots on porous carbon matrix (MoP-QDs@PC) using polyoxometalates (POMs)-contained metal organic frameworks (MOFs) as precursors, where Keggin-type PMo 12 POMs clusters are confined within the zirconium-based UiO-66 MOFs (denoted as PMo 12 @UiO-66). We demonstrate that the as-formed MoC species by in-situ confined carbonization of PMo 12 @UiO-66 can be converted into superhydrophilic MoP-QDs by further phosphorization, while the porous carbon matrix can be converted into rich P and O co-doped carbon matrix, which greatly increase the wettability and the amount of catalytic active sites exposed to the electrolytes. The as-prepared MoP-QDs@PC electrocatalyst exhibits excellent HER performance, which outperforms commercial 20% Pt/C electrocatalyst when overpotential (η) higher than 197 mV and 233 mV under alkaline and acidic conditions, respectively. Depending on the diversity of POMs and MOFs, the current feasible and reliable MoP-QDs@PC electrocatalysts from PMo 12 @UiO-66 precursor would inspire more effective strategies to economical, efficient and stable electrocatalysts for hydrogen evolution. [ABSTRACT FROM AUTHOR]