Sulfur-bridged iron-polyphthalocyanine on CuxO/copper foam: efficient and durable electrocatalyst for overall water splitting

Overall water splitting is a promising route to produce green hydrogen in a sustainable manner. However, its practical large-scale use critically requires efficient, sustainable and easy-to-operate catalysts that can drive both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in the same electrolyte. In this report, we present a facile synthesis of one such electrocatalyst that is composed of amorphous sulfur-bridged iron polyphthalocyanine (FeSPPc) grown in situ on CuxO-coated Cu foam. The material is denoted as FeSPPc/CuxO/CF, where x indicates the non-stoichiometric hybrid valence states of Cu, including its +1 and +2 oxidation states. The as-generated material has unique catalytic sites, large electrochemically active surface area, and high electrical conductivity. It electrocatalyzes the HER in N2-saturated KOH electrolyte (1 M) with a current density of 10 mA cm−2 at an overpotential of only 38 mV. It also electrocatalyzes the OER in O2-saturated KOH solution (1 M) with 10 mA cm−2 at an overpotential of 350 mV. The material is stable while catalyzing both reactions as well. Importantly, a water electrolyzer assembled using FeSPPc/CuxO/CF as both cathode and anode electrodes in the same alkaline electrolyte requires only 1.48 V to drive the reaction with 10 mA cm−2 while remaining stable.