Boosting energy-efficient hydrogen evolution by electronically modulating Ni nodes in a framework for methanol oxidation in fresh and seawater

Abstract

The hydrogen evolution reaction (HER) represents the key step in sustainable energy development. This study presents a novel approach to the HER through value-added formate synthesis utilizing methanol electrolysis in both fresh and seawater environments. This approach leverages electronically modulated nickel nodes of a metal-organic framework (e-Ni MOF) via zinc doping, demonstrating significant enhancement in catalytic performance and energy efficiency owing to the synergistic effects of zinc and nickel, thereby facilitating electron transfer and thus lowering the energy barrier for high-valent Ni-active catalytic phase formation. Specifically, the e-Ni MOF anode-based electrolyzer using a 1.0 M methanol solution in an industrially relevant 30 wt% KOH-seawater electrolyte demonstrated a remarkably lower cell voltage of 1.10 V at 10 mA cm-2. Additionally, it achieved an 11.5-fold higher hydrogen evolution rate by replacing the oxygen evolution reaction (OER) with the methanol oxidation reaction (MeOR). At an industrially relevant current density of 250 mA cm-2, the electrolyzer could lead to an energy saving of 640 W h of electricity compared to a conventional OER system. Moreover, the e-Ni MOF facilitated hydrogen evolution at the cathode and produced formate as a value-added chemical from the MeOR at the anodic side. This dual-benefit approach underscores the potential of e-modulated Ni MOFs in transforming hydrogen evolution processes, offering a sustainable and energy-efficient pathway for hydrogen production from seawater and supporting the goal of carbon-neutral energy solutions. An e-modulated Ni MOF prepared through Zn doping enhances the number of active sites for the formation of a catalytic Ni-OOH phase, thereby accelerating methanol oxidation at the anode and boosting H2 generation at the cathode.