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•Co-Fe binary oxide nanoparticles with unique interfaces were synthesised.•Co-Fe NPs demostrates enhanced HER and OER capabilities.•The synergistic effect at the interface can ...increase electron transfer rate.
Binary transitional metal/metal oxide-based catalysts have been proven to be more effective for catalysing water splitting reactions than their single metal oxide counterparts. Here we have successfully designed and synthesised a binary metal oxide composite consisting of CoO and Fe3O4 phases with special CoO (111)/Fe3O4 (311) interface as bifunctional catalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The Co-Fe binary oxide composite showed the overpotential values of ɳ = 220 mV at −10 mA cm−2 and ɳ = 290 mV at −100 mA cm−2 for HER, and as for the OER performance the catalyst is more efficient than the benchmark catalyst Ir/C requiring the smaller overpotential of η = 369 mV and 406 mV to deliver a current density of 20 mA cm−2 and at 100 mA cm−2, respectively. As a bifunctional catalyst for overall water splitting, the cell can achieve a current density of 10 and 50 mA cm−2 at cell potentials of 1.92 V and 2.05 V, respectively. In addition, the bifunctional electrode also shows long-term water electrolysis stability at a current density of 50 mA cm−2 for 24 h.
Multiwall carbon nanotubes (MWCNTs) have been popularly used as catalyst supports for various electrochemical devices and reactions. In their preparation, surface oxidation by chemical oxidants is ...often necessary to purify MWNCTs, which also results in the formation of oxygen functional groups. However, the effect of these functionalities on electrochemical behavior of MWCNTs for alcohol oxidations remain largely unknown. In this study, we show that surface oxidation activates MWCNTs for electrochemical oxidation of alcohols in alkaline media (0.1 M KOH). Significantly enhanced catalytic activity in terms of higher current density ( j ) as well as lower alcohol oxidation onset potentials was observed following controlled oxidations via chemical or electrochemical methods. High-resolution XPS analysis suggests that the surface bound oxygen functionalities e.g. ketonic group (CO) contribute primarily to the observed increase in catalytic performance. Moreover, to further increase the activity of MWCNTs, hydrothermal treatment was applied to repair the structural damage induced by the harsh oxidation treatment without the sacrifice of oxygen functional groups. Using the hydrothermally treated, surface-oxidized MWCNTs, EtOH undergoes oxidation into acetic acid with ∼99% faradaic efficiency. This study reveals the unique role of oxygen functional groups on MWCNTs towards catalytic alcohol oxidations for possible applications in direct alcohol fuel cells and alcohol sensors.
Palladium (Pd) has been widely used as electrocatalysts for a number of important electrochemical reactions. Herein, we report a facile electrodeposition method for fabrication of nanostructured Pd ...thin films from protic ionic liquids. The electrochemical behavior and electrodeposition of Pd were studied in a protic ionic liquid, ethylammonium nitrate (EAN), compared with aqueous solution and aprotic ionic liquids, 1-ethyl-3-methylimidazolium chloride-tetrafluoroborate (EMIM-Cl-BF 4 ), using cyclic voltammetry and chronoamperometry. The electrodeposition of Pd in protic ionic liquids is found to proceed via an instantaneous nucleation and diffusion-controlled 3D growth mechanism, and accompanied with hydrogen co-evolution at more negative deposition potentials. By controlling the electrodeposition media, electrodeposition potential and time, we show that Pd thin films can be electrodeposited from protic ionic liquids with finely tuned nanostructures and large surface area. The prepared Pd thin films were employed as electrocatalysts for oxygen reduction reactions in alkaline media with an onset potential of 0.95 V (RHE). It was found that Pd films prepared from protic ionic liquids exhibit larger electrochemically active surface area and higher catalytic activity for oxygen reduction reactions than aqueous and aprotic ionic liquid electrolytes under similar electrodeposition conditions.
Amorphous thin films of cobalt oxides with controlled nanostructures and compositions have been prepared by electrodeposition from a room temperature protic ionic liquid for water oxidation ...electrocatalysts. The electrochemical behaviour of Co super(2+) has been studied in ethylammonium nitrate (EAN) using cyclic voltammetry and chronoamperometry. The electrodeposition of Co super(2+) in EAN occurs at -0.95 V vs.Fc super(0/+), followed by hydrogen evolution reaction. The electro-oxidation of Co super(2+) to Co super(3+) is found to be a reversible process in dried EAN at E sub(1/2) = 1.47 V vs.Fc super(0/+). The presence of water significantly affects the voltammetric behaviour of Co super(2+) and the subsequent electrodeposition processes. Cobalt oxides nanostructures have been deposited onto glassy carbon and indium tin oxide (ITO)-coated glass substrates by two routes, (i) controlled-potential deposition of Co, followed by spontaneous air oxidation and (ii) controlled-potential deposition of Co followed by anodic oxidation in the presence of water. SEM, EDX, XRD and XPS reveal that cobalt oxides of different morphologies and chemical compositions are formed on the surface of electrodes. The cobalt oxides films exhibit catalytic activity towards water oxidation reaction in neutral phosphate buffered solution with low overpotentials.
Invited for this month's cover is the group of Prof. Douglas R. MacFarlane at Monash University. The Cover picture depicts the electrocatalytic synthesis of ammonia on Ru clusters supported on ...carbon. The Full Paper itself is available at 10.1002/cssc.201801632.
“Here, we are exploring ways to develop a game‐changing process…” This and more about the story behind the research that inspired the Cover image is presented in the Cover Profile. Read the full text of the corresponding research at 10.1002/cssc.201801632. View the Front Cover here: 10.1002/cssc.201802148.
Carbon black (CB) is popularly used as a catalyst support for metal/metal oxide nanoparticles due to its large surface area, excellent conductivity and stability. Herein, we show that surface ...oxidized CB itself, after acidic treatment and electrochemical oxidation, exhibits significant catalytic activity for the electrochemical oxidation of water and alcohols.
Surface oxidized carbon black after acidic treatment and electrochemical oxidation exhibits significant catalytic activity for the electrochemical oxidation of water and alcohols.
Multiwall carbon nanotubes (MWCNTs) have been applied extensively in various aspects of advanced materials development. However, the purification of multi-walled carbon nanotubes and the removal of ...internally confined metal impurities, without compromising the CNT structural integrity, have proved to be a great challenge. The presence of inherent metal impurities has increased the complexity and health risks associated with the use of MWCNTs. In this study, we developed a low-cost purification strategy to effectively remove encapsulated metal impurities. MWCNTs synthesized by Ni-catalyzed chemical vapor deposition (CVD), were annealed in the presence of melamine under Ar-atmosphere protection at 1000 °C. Electron microscopy indicated that the pyrolysis of MWCNTs in the presence of melamine induces the leaching of encapsulated Ni particles
via
the tube open-end or the defect sites found along the MWCNTs. With this method, the leached impurities were shown to be more susceptible and accessible to acid purification. Upon acid treatment, ultrapure MWCNTs with trace amounts of metallic impurities (<0.01 wt%) can be achieved. Alternatively, the leached metal nanoparticles could serve as highly efficient electrocatalytically active sites for oxygen evolution reactions with a turn over frequency (TOF) of 0.61 s
−1
.
Melamine is used to induce leaching of encapsulated metal impurities in MWCNTs. The leached impurities can be effectively removed or utilized as electrocatalytically active centres.
The Front Cover shows nitrogen molecules (N2) reacting to form ammonia (NH3) at ambient temperatures and pressure on small Ru clusters distributed over a substrate of carbon. The Ru catalyst supports ...the reduction reaction at low overpotentials where the production of hydrogen as a byproduct is minimized. The production of ammonia from renewable energy is a vital step towards a carbon‐free society since ammonia today is produced from fossil‐fuel‐based hydrogen. More information can be found in the Full Paper by Wang et al. on page 3416 in Issue 19, 2018 (DOI: 10.1002/cssc.201801632).
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