Hollow Carbon Cages Derived from Polyoxometalate-Encapsuled Metal-Organic Frameworks for Energy-Saving Hydrogen Production

The electrocatalytic conversion of water-to-hydrogen powered by renewable energy is one of the promising strategies to unravel the energy and environment crises. However, a such process usually costs large energy consumption owing to the low efficiency of anodic oxygen evolution reaction (OER), which is another vital half reaction of the overall water splitting (OWS) system. Herein, we designed and fabricated hollow nitrogen-doped carbon nanocages loaded with Ni3N and Co nanoparticles derived from polyoxometalate-encapsuled metal-organic frameworks. The catalyst exhibited appealing dual functions for both OER and hydrogen evolution reaction (HER), outperforming the Ni-free and solid samples. Notably, the designed catalyst also showed much enhanced electrochemical performance for glycerol/glucose oxidation reaction when compared with OER. The home-made two-electrode electrolyzer, coupled HER with polyalcohol or glucose oxidation reaction, only needs cell voltages of 1.125 and 1.557 V to reach 10 mA cm(-2), respectively, which are much smaller than that in 1 M KOH (2.087 V), demonstrating a large amount of energy saving for hydrogen production.