We recently reported the fastest anodization method (just 80 s) of all for accessing a denser array of Cu(OH) 2 −CuO nanoneedles on a Cu foil substrate by applying a constant potential of 0.864 V vs a reversible hydrogen electrode in 1.0 M KOH that delivered a better activity for the methanol oxidation reaction (MOR). In this study, we show that the strength of the KOH solution used for anodization alters the size, morphology, surface chemistry, electrochemical accessibility of Cu sites, and the subsequent MOR activity trend. Intriguingly, an increase in KOH solution strength shortens the time of anodization from 80 s (1.0 M KOH) to 20 s with 3.0 M KOH, which in turn drastically reduces to just 6 s with 6.0 M KOH. As of now, this is the shortest time ever achieved for the anodic growth of Cu−OH/O nanoneedles on a Cu substrate. A set of detailed and comparative physical and electrochemical characterizations reveal positive relationships between anodization pH and anodization current, the size of Cu− OH/O nanoneedles grown, rate of growth, electrochemical accessibility of Cu sites, and electrocatalytic MOR activity. Thus, this study provides a universal approach to control the size of Cu−OH/O nanoneedles, electrochemical accessibility of Cu sites, and their subsequent MOR activity.

Complete electrooxidation of methanol in alkaline conditions is catalyzed efficiently by 3d transition metal-based oxides and hydroxides with no issues of mass-transport limitations. Among them, the oxides and hydroxides of Cu prepared using various methods were said to be exceptional. In this work, the methanol oxidation reaction (MOR) activity of such a copper oxide/hydroxide catalyst is advanced by making use of the three-dimensional (3D) configuration of the Cu foam substrate and inherent Ni impurity present in it. The 3D configuration of the Cu foam substrate enabled a larger active surface area per unit geometrical area. The MOR current densities 110 and 310 mA cm–2 at 0.60 and 0.75 V vs Hg/HgO, respectively, testify the outstanding MOR activity of Cu–O/OH nanowires with Ni impurity (Cu–O/OH­(Ni)). Excellent chronoamperometric stability at 0.55 V vs Hg/HgO and relatively lower activation energy at all potentials in the catalytic turnover region further ascertain the superiority of Cu–O/OH­(Ni). Specific activity measurements implied that Cu–O/OH­(Ni) benefited from intrinsic activity enhancement by the presence of inherent Ni impurity. This work, thus, reveals a facile way of enhancing the MOR activity of Cu-based MOR electrocatalysts.

Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH 2 ) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more di cult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.

Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH2) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more difficult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.

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