Promote the electrocatalysis activity of amorphous FeOOH to oxygen evolution reaction by coupling with ZnO nanorod array

Unveiling the potential of amorphous nanocatalysts in membrane-based hydrogen production

Hydrogen, as a clean and renewable energy source, is a promising candidate to replace fossil fuels and alleviate the environmental crisis. Compared with the traditional H-type cells with a finite-gap, the design of membrane electrodes can reduce the gas transmission resistance, enhance the current density, and improve the efficiency of hydrogen production. However, the harsh environment in the electrolyser makes the membrane electrode based water electrolysis technology still limited by the lack of catalyst activity and stability under the working conditions. Due to the abundant active sites and structural flexibility, amorphous nanocatalysts are alternatives. In this paper, we review the recent research progress of amorphous nanomaterials as electrocatalysts for hydrogen production by electrolysis at membrane electrodes, illustrate and discuss their structural advantages in membrane electrode catalytic systems, as well as explore the significance of the amorphous structure for the development of membrane electrode systems. Finally, the article also looks at future opportunities and adaptations of amorphous catalysts for hydrogen production at membrane electrodes. The authors hope that this review will deepen the understanding of the potential of amorphous nanomaterials for application in electrochemical hydrogen production, facilitating future nanomaterials research and new sustainable pathways for hydrogen production.

One-Step High-Temperature Electrodeposition of Fe-Based Films as Efficient Water Oxidation Catalysts

Electrolysis of water to produce hydrogen requires an efficient catalyst preferably made of cheap and abundant metal ions for the improved water oxidation reaction. An Fe-based film has been deposited in a single step by electrochemical deposition at temperatures higher than the room temperature. Until now, the electrodeposition of iron oxide has been carried out at 298 K or at lower temperatures under a controlled atmosphere to prohibit atmospheric oxidation of Fe²⁺ of the iron precursor. A metal inorganic complex, ferrocene, and non-aqueous electrolyte medium propylene carbonate have been used to achieve electrodeposition of iron oxide without the need of any inert or controlled atmosphere. At 298 K, the amorphous film was formed, whereas at 313 K and at higher temperatures, the hematite film was grown, as confirmed by X-ray diffraction. The transformation of iron of the ferrocene into a higher oxidation state under the experimental conditions used was further confirmed by X-ray photoelectron spectroscopy, ultraviolet-visible, and electron paramagnetic resonance spectroscopic methods. The films deposited at 313 K showed the best performance for water oxidation with remarkable long-term electrocatalytic stability and an impressive turnover frequency of 0.028 s^-1 which was 4.5 times higher than that of films deposited at 298 K (0.006 s^-1). The observed overpotential to achieve a current density of 10 mA cm^-2 was found to be 100 mV less for the film deposited at 313 K compared to room-temperature-derived films under similar experimental conditions. Furthermore, electrochemical impedance data revealed that films obtained at 313 K have the least charge transfer resistance (114 Ω) among all, supporting the most efficient electron transport in the film. To the best of our knowledge, this is the first-ever report where the crystalline iron-based film has been shown to be electrodeposited without any post-deposition additional treatment for alkaline oxygen evolution reaction application.

Robust FeCoP nanoparticles grown on a rGO-coated Ni foam as an efficient oxygen evolution catalyst for excellent alkaline and seawater electrolysis

Electrochemical water splitting is a potential green hydrogen energy generation technique. With the shortage of fresh water, abundant seawater resources should be developed as the main raw material for water electrolysis. However, since the precipitation reaction of chloride ions in seawater will compete with the oxygen evolution reaction (OER) and corrode the catalyst, seawater electrolysis is restricted by the decrease in activity, low stability, and selectivity. Rational design and development of efficient and stable catalysts is the key to seawater electrolysis. Herein, a high-activity bimetallic phosphide FeCoP, grown on a reduced graphene oxide (rGO)-protected Ni Foam (NF) substrate using FeCo Prussian Blue Analogue (PBA) as a template, was designed for application in alkaline natural seawater electrolysis. The OER activity confirmed that the formed FeCoP@rGO/NF has high electrocatalytic performance. In 1 M KOH and natural alkaline seawater, the overpotential was only 257 mV and 282 mV under 200 mA cm^-2, respectively. It also demonstrated long-term stability up to 200 h. Therefore, this study provides new insight into the application of PBA as a precursor of bimetallic phosphide in the electrolysis of seawater at high current density.

Design and Synthesis of Lead(II)-Based Electrocatalysts for Oxygen Evolution Reaction

A well-organized worldwide effort in providing remedies to sustainable clean energy generation and storage has focused on the strategic design and development of stable and efficient earth-abundant metal (Fe, Co, Ni, Pb, etc.)-based electrocatalysts for the oxygen evolution reaction (OER). Unfortunately, examples of Pb-based catalysts for such a process are rare. In this work, based on the dual-linker strategy, we have designed and synthesized two new two-dimensional (2D) coordination polymers of Pb with the hcb topology, [Pb₂(tpbn)(adc)₂]·4H₂O·0.5CH₃OH}_n (CP1) and {[Pb₂(tpbn)(fum)₂]·7H₂O}_n (CP2), in excellent yields by the room-temperature self-assembly of Pb(OAc)₂, tpbn, and H₂adc or H₂fum (where tpbn = N,N',N‴,N‴'-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane, H₂adc = acetylene dicarboxylic acid, and H₂fum = fumaric acid). In addition to determining their X-ray single crystal structures, the phase purity and thermal stability were established by powder X-ray diffraction and thermogravimetric analysis, respectively. Furthermore, these were also characterized by the microscopic techniques (SEM/EDX and TEM/HRTEM). For their conductive and highly stable nature in alkaline medium, both CP1 and CP2 were tested for their suitability in the OER process. Interestingly, with a subtle change from adc in CP1 to fumarate in CP2 as the dicarboxylate linker, the latter performed much better than the former and displayed an excellent electrochemical stability in basic medium. Remarkably, CP2 has one of the lowest Tafel values (35 mV dec^-1) and a low overpotential value (140 mV vs RHE) in 0.5 M KOH compared to those reported for any materials. Such a comparative study with CP1 and CP2, which are the simplest CPs and made with green-chemistry protocols for an easy making in large quantities, provides an outlook to developing the next-generation Pb-based electrocatalysts.

Amorphous NiSn and FeOOH as bifunctional co-catalysts for oxygen reduction and phenol (water) oxidation over BiVO4 under visible light

Monoclinic BiVO₄ (BiV) has been widely used as a photoanode for water oxidation, but rarely as a photocatalyst for organic oxidation due to slow reaction of O₂. In this work, BiV has been modified with poorly crystallized sFe and sNi, where sFe is FeOOH, and sNi is a mixture of Ni(OH)₂ and polysulfide. Under light, sFe/BiV and sNi/BiV in aqueous solution were more active than BiV, respectively, not only for phenol oxidation but also for O₂ reduction. Importantly, the rate of phenol oxidation obtained for sFe/sNi/BiV was larger than the sum of the rates measured for sFe/BiV and sNi/BiV, by a factor of approximately 1.5. Moreover, on a film electrode, O₂ reduction had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV, while water (photo)oxidation had a current of sFe/sNi/BiV > sNi/BiV > sFe/BiV > BiV. A possible mechanism is proposed, involving formation of a reduced sulfur species for O₂ reduction and an oxidized iron species for phenol oxidation. In sFe/sNi/BiV, there is a mutual promotion between the sNi-mediated electron transfer and the sFe-mediated hole transfer. This results in a further improved efficiency of charge separation for O₂ reduction and phenol oxidation.

Fabrication of photo-Fenton self-cleaning PVDF composite membrane for highly efficient oil-in-water emulsion separation

The anti-fouling performance of membranes is an important performance in the separation of oil/water.

Nanoscale design of 1D metal oxides derived from mixed Ni-MH battery/transition metal dust

Controllable recycling of End-of-life rechargeable nickel-metal hydride (Ni-MH) batteries and by-products of steelmaking to added-value functional nanostructures is desired but challenging. The present work introduces an innovative and high-yield microrecycling strategy to simultaneous synthesis of TM alloy (i.e., Ni-based superalloy) and RE oxide (REO) nanostructures from obsolete Ni-MH batteries mixed with zinc-rich electric arc furnace dust (EAFD). This strategy involves integration of high-temperature thermal isolation followed by thermal nanowiring techniques. The impure thermally-isolated REOs were purified and transformed into one dimensional (1D) nanorods of hybrid REOs. Besides, during high-temperature thermal isolation, defect-rich ZnO with tailored structures of nanorods and nanoribbons were fabricated using controllable vapour deposition. The electrochemical performance of ZnO nanoribbons for oxygen evolution reaction (OER) revealed a considerable overpotential reduction of 131 mV (18%) compared to pure commercial nano-ZnO. This approach is transformational in providing a scalable and cost-effective pathway to facilitate recycling of the challenging, yet critical, waste materials into functional nanostructures for energy and environmental applications.