Abdul Qayum

Bio: Abdul Qayum is an academic researcher from Shandong University. The author has contributed to research in topics: Water splitting & Overpotential. The author has an hindex of 4, co-authored 7 publications receiving 66 citations.

In situ conversion of metal (Ni, Co or Fe) foams into metal sulfide (Ni3S2, Co9S8 or FeS) foams with surface grown N-doped carbon nanotube arrays as efficient superaerophobic electrocatalysts for overall water splitting

Abstract: High-efficiency electrocatalysts at large current densities require consideration of not only the intrinsic activities but also the surface geometric structures. Here, we report a simple strategy to obtain metal sulfide (Ni3S2, Co9S8 and FeS) foams by in situ conversion of commercial Ni, Co and Fe foams through a conventional annealing reaction. Interestingly, N-doped carbon nanotubes, which are catalyzed by the corresponding metal sulfide nanocrystals, can also be obtained on the surface of the foams. The as formed Ni3S2 foams can work as bifunctional electrodes for overall water splitting with a potential of 1.5 V and 1.72 V at a current density of 10 mA cm−2 and 100 mA cm−2, respectively, which are comparable to the state-of-the-art transition-metal-sulfide-based bifunctional electrocatalysts reported to date. Factors such as abundant electrocatalytic active sites and excellent conductivity contribute to the gas evolution properties of nickel sulfide foams. Interestingly, the prominent performance of the nickel sulfide foams is also due to the nanotube array coating which provides special superaerophobic structures. The unique surface geometry provides little solid–gas contact area (solid content as low as 2%) at the electrode/bubble interface, and ultrasmall gas bubbles with diameters below 100 μm can leave the surface of the electrodes with ease, which effectively reduces the bubble overpotential and greatly promotes gas evolution properties especially at high current densities. Our research provides a facile strategy to obtain superaerophobic surface geometry for in situ prepared transition metal sulfide foams, which can work as bifunctional electrocatalysts for overall water splitting at large current densities. These findings may bring new insights in the design of efficient electrocatalysts for overall water splitting.

An in situ combustion method for scale-up fabrication of BiVO4 photoanodes with enhanced long-term photostability for unassisted solar water splitting

Abstract: The development of large-area, low-cost photoanodes with high efficiency and photostability is pivotal for the commercialization of photoelectrochemical (PEC) water splitting. Here, an in situ combustion process is reported as a new route to the solution growth of bismuth vanadate (BiVO4) photoanodes. The highly exothermal in situ combustion process ignites rapid solvent evaporation and promotes the homogeneous distribution of BiVO4 on large-size conductive substrates. Also, the released thermal energy builds tight connection between the BiVO4 films and the conductive substrates, which suppresses the cathodic photocorrosion and shows unexpected high photocurrent density and ultralong photostability. The as-formed photoanodes can continuously work for sulfite oxidation under consecutive AM 1.5G illumination for ∼190 h with no decay, and for water oxidation for ∼135 h with ∼20% performance decay compared with the initial value. Such a high photostability toward water oxidation has not been reported for large-size BiVO4 photoanodes previously. A PEC-PV device is fabricated by assembling 9 pieces of combustion-processed large size (25 cm2) BiVO4 photoanodes for unassisted solar water splitting. The as-assembled device shows a stable photocurrent of up to 0.26 A even after working for 40 sunny days under real solar light irradiation (1 h for each day). Such a facile in situ solution combustion method is promising for scale-up fabrication of large size BiVO4 photoanodes, and it can also potentially be implemented to fabricate other types of photoelectrodes on conductive substrates and promote their large-scale deployment.

Unexpected Photoinduced Room Temperature Magnetization in Bi 2 WO 6 Nanosheets

Abstract: The current investigation in magnetism in 2D materials offers new opportunities for studying spintronics at low dimensions. Here, reversible photoinduced room temperature magnetization in 2D Bi2 WO6 nanosheets is reported for the first time. Compared with the original state, the ultraviolet (UV)-illuminated Bi2 WO6 nanosheets show a yellow-green color change and significantly enhanced magnetic signals (saturated magnetization (Ms ) increased from 0.002 to 0.12 emu g-1 ). X-ray photoelectron spectroscopy (XPS) results show unexpected W reduction (W6+ to W5+ /W4+) and Bi oxidation (Bi3+ to Bi5+ ) upon UV illumination for the Bi2 WO6 nanosheets, indicating a photoexcited Bi to W charge transfer. Density functional theory (DFT) calculations indicate spontaneous spin polarization of the Bi2 WO6 nanosheets in the excited metastable state. Meanwhile, thicker Bi2 WO6 nanoplates or nanoparticles show no enhanced magnetic signals upon UV illumination. UV illumination of the thin Bi2 WO6 nanosheets can induce the formation of internal electric field (polarization), leading to structural deformation/lattice distortion (photostriction). The photoexcited electrons are trapped in the WO6 layers while the photogenerated holes are trapped in the Bi2 O2 layers, leading to spin polarization and enhance the magnetization. The research may bring some new insights in tuning the magnetic properties of 2D nanostructures.

Recent advances in transition-metal-sulfide-based bifunctional electrocatalysts for overall water splitting

Abstract: Hydrogen produced via water electrolysis can act as an ideal clean chemical fuel with superb gravimetric energy density and high energy conversion efficiency, solving the problems of conventional fossil fuel exhaustion and environmental contamination. Transition metal sulfides (TMS) have been extensively explored as effective, widely available alternatives to precious metals in overall water splitting. Herein, recent advances, covering preparation methods, intrinsic electrocatalytic performance, and optimization strategies, relating to TMS-based bifunctional electrocatalysts have been summarized systematically and comprehensively. Firstly, a general introduction to the reaction mechanisms and key parameters of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is provided. Next, the physicochemical properties of TMS and typical synthesis methods are introduced to give guidance for fabricating TMS materials with well-defined structures, controllable compositions, and excellent performance. Importantly, the intrinsic activities of TMS-based electrocatalysts and several strategies for improving their bifunctional electrocatalytic performance during water electrolysis are discussed in detail. Finally, perspectives covering the challenges and opportunities related to the further development of TMS-based materials with high activity and long-term durability for overall water splitting are given. The aim herein is to provide guidelines for the design and fabrication of TMS-based bifunctional electrocatalysts with excellent performance and to accelerate their large-scale practical application in water electrolysis.