The anode oxygen evolution reaction (OER) is knownt ol argely limit the efficiency of electrolyzerso wing to its sluggish kinetics.W hile crystalline metal oxides are promising as OER catalysts,t heir amorphous phases also show high activities.E fforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 gi no ne batch) is presented with homogeneous elemental distribution via afacile supersaturated co-precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes af aster surface self-reconstruction process during OER, forming am etal oxy(hydroxide) active layer with rich oxygen vacancies,leading to superior OER activity (280 mV overpotential at 10 mA cm À2 in 0.1m KOH). This opens up the potential of fast, facile,a nd scaleup production of amorphous metal oxides for high-performance OER catalysts.

Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction.

The anode oxygen evolution reaction (OER) is knownt ol argely limit the efficiency of electrolyzerso wing to its sluggish kinetics.W hile crystalline metal oxides are promising as OER catalysts,t heir amorphous phases also show high activities.E fforts to produce amorphous metal oxides have progressed slowly, and how an amorphous structure benefits the catalytic performances remains elusive. Now the first scalable synthesis of amorphous NiFeMo oxide (up to 515 gi no ne batch) is presented with homogeneous elemental distribution via afacile supersaturated co-precipitation method. In contrast to its crystalline counterpart, amorphous NiFeMo oxide undergoes af aster surface self-reconstruction process during OER, forming am etal oxy(hydroxide) active layer with rich oxygen vacancies,leading to superior OER activity (280 mV overpotential at 10 mA cm À2 in 0.1m KOH). This opens up the potential of fast, facile,a nd scaleup production of amorphous metal oxides for high-performance OER catalysts.

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