Neutral, eco-friendly HER: Copper complex (CuL) was immobilized on to the carbon supports via non-covalent interactions. One of them, CuL/GO, possesses a low overpotential of 139 mV at −10 mA/cm² in natural seawater. In addition, the performances of CuL/GO were boosted up when performed in seawater sample in comparison to the HER in a NaCl electrolyte.

Abstract

Electrochemical hydrogen evolution reaction (HER) is an appealing strategy to utilize renewable electricity to produce green H₂. 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 N₄-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 H₂ 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/cm². This demonstrated the potential use of CuL/GO as an effective HER catalyst in seawater for further sustainable development.