Herein, we report a facile solvothermal process to synthesize an active electrocatalyst for the oxygen evolution reaction (OER) in an alkaline medium by anchoring nanosheets of a NiZn double hydroxide over nitrogen doped reduced graphene oxide after enriching the system with the γ-NiOOH phase. This catalyst possesses a thin, porous and open layered structure, which makes the system more efficient and accessible for a better electrochemical water oxidation reaction. Moreover, we experimentally demonstrated that incorporation of Zn via a single-step solvothermal method provides an easy approach to obtain plenty of exposed γ-NiOOH phases to make the system more viable for OER with a small overpotential of 290 mV at 10 mA cm and a Tafel slope of 44 mV per decade. In addition to this, the oxophilic nature of Zn in the (Zn)Ni-LDH/N-rGO catalyst helps to improve the long-term stability of the whole system. The obtained results open up possibilities for the design of future robust OER electrocatalysts by the use of very cheap and abundant materials like Ni and Zn in place of expensive Ir and Ru in the present commercial electrocatalysts.

The size-controlled growth of nanocrystalline Fe-Fe2O3 particles (2-3 nm) and their concomitant dispersion on N-doped graphene (Fe-Fe2O3/NGr) could be attained when the mutually assisted redox reaction between NGr and Fe(3+) ions could be controlled within the aqueous droplets of a water-in-oil emulsion. The synergistic interaction existing between Fe-Fe2O3 and NGr helped the system to narrow down the overpotential for the oxygen reduction reaction (ORR) by bringing a significant positive shift to the reduction onset potential, which is just 15 mV higher than its Pt-counterpart. In addition, the half-wave potential (E1/2) of Fe-Fe2O3/NGr is found to be improved by a considerable amount of 135 mV in comparison to the system formed by dispersing Fe-Fe2O3 nanoparticles on reduced graphene oxide (Fe-Fe2O3/RGO), which indicates the presence of a higher number of active sites in Fe-Fe2O3/NGr. Despite this, the ORR kinetics of Fe-Fe2O3/NGr are found to be shifted significantly to the preferred 4-electron-transfer pathway compared to NGr and Fe-Fe2O3/RGO. Consequently, the H2O2% was found to be reduced by 78.3% for Fe-Fe2O3/NGr (13.0%) in comparison to Fe-Fe2O3/RGO (51.2%) and NGr (41.0%) at -0.30 V (vs. Hg/HgO). This difference in the yield of H2O2 formed between the systems along with the improvements observed in terms of the oxygen reduction onset and E1/2 in the case of Fe-Fe2O3/NGr reveals the activity modulation achieved for the latter is due to the coexistence of factors such as the presence of the mixed valancies of iron nanoparticles, small size and homogeneous distribution of Fe-Fe2O3 nanoparticles and the electronic modifications induced by the doped nitrogen in NGr. A controlled interplay of these factors looks like worked favorably in the case of Fe-Fe2O3/NGr. As a realistic system level validation, Fe-Fe2O3/NGr was employed as the cathode electrode of a single cell in a solid alkaline electrolyte membrane fuel cell (AEMFC). The system could display an open circuit voltage (OCV) of 0.73 V and maximum power and current densities of 54.40 mW cm(-2) and 200 mA cm(-2), respectively, which are comparable to the performance characteristics of a similar system derived by using 40 wt% Pt/C as the cathode electrode.

This work introduces the synthesis and water oxidation reaction of the N-doped entangled graphene framework (NEGF) decorated with NiFe-LDH nanostructures (NiFe-LDH/NEGF) showing improved catalytic durability owing to its open and porous 3D structure.

Currently, the low energy efficiency of water electrolysis has compelled research toward the development of novel and energy‐effective strategies for low‐cost H2 generation. In this context, we report a new concept of simultaneous H2 and electricity generation by separating out the exothermic self‐sustained Al−H2O reaction via electrochemistry. In addition, to catalyze the cathodic water reduction reaction, a single‐pot and environmentally benign synthesis method is adopted. It results in the design of an electrocatalyst composed of Co@CoAl‐layered double hydroxide core‐shell nanospheres anchored over in situ generated N‐doped graphene. Toward the water reduction reaction, the designed catalyst shows a negative voltage shift of mere around 113 mV with respect to the commercial Pt/C catalyst to reach the benchmark 10 mA cm−2, with excellent stability of approximately 86 % voltage retention after 12 h of continuous operation. The catalytic superiority of our material is evident when taken for battery‐level testing; the fabricated device was able to deliver an average output voltage of around 0.95 V at a discharge current density of 5 mA cm−2 along with H2 liberation, which was also detected and quantified through gas chromatography.

The large-scale application of water electrolysis for the generation of hydrogen can be made viable only by the development of inexpensive, robust, and bifunctional electrocatalysts. Here, we report a self-templating method for the design of porous, edge-site-rich hybrid nanomaterials via the selective etching of layered double hydroxide precursors that contain an amphoteric metal by alkali treatment, followed by vapor phase selenization. The obtained hexagonal nickel selenide nanoplates anchored over nitrogen-doped graphene showed highly efficient and robust oxygen evolution reaction (OER) electrocatalysis due to the inherent in situ electrochemical oxidation property of selenides demonstrating low overpotential of 311 mV to achieve the 10 mA cm −2 water oxidation current density in 1 M KOH. The faster reaction kinetics and long-term stability of the catalyst encouraged us to demonstrate a real alkaline water electrolyzer, which enables high-performing overall water splitting with a low overpotential of 460 mV from theoretical potential of 1.23 V to generate sufficient amounts of H 2 and O 2 by achieving a current density of 10 mA cm −2 . This study thus provides a valuable strategy to tailor the surface texture of the catalyst as well as its effectiveness in developing robust multifunctional electrocatalysts, promoting the efficient design of porous materials for catalytic applications.

Substituting the energy-uphill water oxidation half-cell with readily oxidizable urea-rich urine, a ground-breaking bridge is constructed, combining the energy-efficient hydrogen generation and environmental protection. Hence, designing a robust multifunctional electrocatalyst is desirable for widespread implementation of this waste to fuel technology. In this context, here, we report a simple tuning of the electrocatalytically favorable characteristics of NiCo-layered double hydroxide by introducing [MoS4]2– in its interlayer space. The [MoS4]2– insertion as well as its effect on the electronic structure tuning is thoroughly studied via X-ray photoelectron spectroscopy in combination with electrochemical analysis. This insertion induces overall electronic structure tuning of the hydroxide layer in such a way that the designed catalyst exhibited favorable kinetics toward all the required reactions of hydrogen generation. This is why our homemade catalyst, when utilized both as a cathode and anode to fabricate a urea electrolyzer, required a mere ∼1.37 V cell potential to generate sufficient H2 by reaching the benchmark 10 mA cm–2 in 1 M KOH/0.33 M urea along with long-lasting catalytic efficiency. Other indispensable reason of selecting [MoS4]2– is its high-valent nature making the catalyst highly selective and insensitive to common catalyst-poisoning toxins of urine. This is experimentally supported by performing the real urine electrolysis, where the nanospike-covered Ni foam-based catalyst showed a performance similar to that of synthetic urea, offering its industrial value. Other intuition of selecting [MoS4]2– was to provide a ligand-based mechanism for hydrogen evolution half-cell [hydrogen evolution reaction (HER)] to preclude the HER-competing oxygen reduction. Another crucial point of our work is its potential to avoid the mixing of two explosive product gases, that is, H2 and O2.

Correction for 'Nanocrystalline Fe-Fe 2 O 3 particle-deposited N-doped graphene as an activity-modulated Pt-free electrocatalyst for oxygen reduction reaction' by Vishal M. Dhavale et al., Nanoscale, 2015, 7, 20117-20125. It has been brought to our attention that there is a mistake in our published paper, Nanoscale, 2015, 7, 20117-20125. On page 20120, the scale bars for the high-resolution transmission electron microscopy image in Fig. 1d and the highlighted portion presented in Fig. 1e are not correct. In the corrected figure shown below we present the images with their rectified scale bars.

Both mechanically and electrically rechargeable zinc-air batteries (ZAB) have received much interest due to their high energy density and suitability for mobile and stationary applications. However, their commercialization has been...