Electrocatalytic Hydrogen Evolution of Immobilized Copper Complex on Carbonaceous Materials: From Neutral Water to Seawater

Abstract Electrochemical hydrogen evolution reaction (HER) is an appealing strategy to utilize renewable electricity to produce green H 2 . Moreover, use of neutral‐pH electrolyte such as water and seawater for the HER has long been desired for eco‐friendly energy production that aligns with net zero emission goal. Herein, new heterogeneous catalysts were developed by dispersing an HER‐active copper complex containing N 4 ‐Schiff base macrocycle (CuL) on carbonaceous materials, i. e . multi‐walled carbon nanotube (CNT) and graphene oxide (GO), via non‐covalent interaction and investigated their HER performance. It was found that CuL/GO exhibited higher HER activity than CuL/CNT, possibly due to its significantly larger amount of CuL immobilized onto GO. In addition, CuL/GO showed satisfactory HER performance in a neutral (pH 7) NaCl electrolyte solution. Notably, the performances of CuL/GO were boosted up when performed in natural seawater sample with the faradaic efficiency of 70 % and 3 times higher amount of H 2 at −0.6 V vs reversible hydrogen electrode (RHE), in comparison to the HER in a NaCl electrolyte. Furthermore, it possessed a low overpotential of 139 mV at −10 mA/cm 2 . This demonstrated the potential use of CuL/GO as an effective HER catalyst in seawater for further sustainable development.