Universal molecular-confined synthesis of interconnected porous metal oxides-N-C frameworks for electrocatalytic water splitting

The rational synthesis of high performance electrocatalysts at low cost for water splitting (hydrogen and oxygen evolution reaction, HER and OER) is highly desirable but remains a key challenge. Herein, we report a versatile molecular-confining route to construct strongly coupled metal oxides-N-C frameworks with interconnected configuration. By simply chelating various transition metal ions with ethylenediaminetetraacetic acid disodium salt (EDTA) in agarose hydrogel and subsequent carbonization, the high specific surface area porous N-C frameworks with strongly coupled metal oxides (e.g., manganese, iron, cobalt, nickel and their mixed oxides) can be prepared as advanced nonprecious water splitting electrocatalysts. For instance, the resulting Co3O4-N-C frameworks with the high surface area of 153m(2) g(-1), and the moderate nitrogen content of 1.23%, require an overpotential of 324 mV to afford a current density of 10 mA cm(-2) in 0.1M KOH for OER, superior to commercial RuO2 catalysts. Density functional theory (DFT) calculations reveal that the strong coupling between N-C and Co3O4 tunes the local electronic structure of Co for high-valence active sites and assures optimal adsorption energies of OER intermediates. Moreover, Co2P-N-C electrocatalysts derived from Co3O4-N-C also exhibit excellent HER performance under 1.0M KOH with a low overpotential of 139 mV to reach 10 mA cm(-2), a small Tafel slope of 45 mV dec(-1) and impressive stability, underscoring the versatility of our synthetic strategy.