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Electrocatalysts play a crucial role in hydrogen production via water electrolysis. In this presentation, we report the synthesis of atomically dispersed ruthenium (Ru) supported on nitrogen-doped carbon (Ru-NC) with ultra-low Ru loading (0.2 wt%) through a two-step deposition-pyrolysis method. Briefly, controlled amounts of ammonium alginate (AG), 20% wt., were dispersed on a carbonaceous support (Norit CN-1) followed by subsequent introduction of the ruthenium precursor (RuCl3·3H2O) under alcoholic solution (1-butanol). Finally, the Ru-containing solids were pyrolized at 800 ºC for 2 h under N2 flow to yield the Ru-NC catalyst. Extensive transmission electron microscopy investigations reveal that Ru is dispersed on the NC support in the form of both single atoms and small clusters (Figure 1a). The as-prepared Ru-NC exhibits superior electrocatalytic activity and good stability for both HER and OER, showing bifunctionality. It only requires a low overpotential of 47.1 and 72.8 mV to deliver a current density of 10 mA cm-2 for HER in 0.5 M H2SO4 and 1.0 M KOH, respectively, and 300 mV for OER in 1.0 M KOH. The overall water electrolysis performance has been investigated in alkaline solution using Ru-NC as both HER and OER catalysts in the presence of an anion exchange membrane water electrolysis (AEM-WE), where a cell voltage of 1.67 V is needed to achieve 10 mA cm-2. Furthermore, with a bipolar membrane (BPM), we demonstrate water electrolysis in acid-alkaline dual electrolytes (BPM-WE), where HER is accomplished in a kinetically favorable acidic solution and OER in a kinetically favorable basic solution. Such asymmetric acid-alkaline BPM-WE operates under a low cell voltage of only 0.89 V to deliver a current density of 10 mA cm-2 and can sustain over 100 hours without significant performance decay due to the assistance of electrochemical neutralization resulting from the crossover of the electrolytes, which shows a great potential for energy-saving hydrogen production. Figure 1 |
