Trace Ru atoms implanted into a Ni/Fe-based oxalate solid-solution-like with high-indexed facets for energy-saving overall seawater electrolysis assisted by hydrazine

Seawater splitting is considered as an economically appealing yet technically challenging approach to generate hydrogen fuel. Hampered by the sluggish oxygen evolution reaction (OER) and the detrimental effects of chlorine electrochemistry, designing robust and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) in parallel with the hydrazine oxidation reaction (HzOR) is extremely imperative for hydrogen production in seawater mediums. Herein, we present a protocol that implants Ru nanospecies into a Ni/Fe-oxalate solidsolution-like with high-indexed facets to engineer an effective and novel-structured catalyst (Ru-(Ni/Fe)C2O4). Systematic experimental analyses alongside the theoretical calculations reveal that the synergistic effect of Ru nanospecies and high-index facets from (Ni/Fe)C2O4 endows Ru-(Ni/Fe)C2O4 with extraordinary activities of HER, OER and HzOR. When assembled into an electrolyzer, the cell voltage reduces to 0.01 V at 10 mA cm-2 for HER-HzOR coupling seawater splitting. Moreover, the system remains stable under 500 mA cm-2 at 80 degrees C for 50 h, almost meeting the requirements for quasi-industrial electrolysis. This work proposes a guideline for preparing multifunctional electrocatalysts and provides an effective strategy for developing seawater electrolysis to achieve a hydrogen economy society.

Automated summary

Designing robust and highly efficient electrocatalysts for seawater splitting is crucial for hydrogen production. In this study, Ru nanospecies were implanted into a Ni/Fe-oxalate solid solution with high-indexed facets, resulting in an effective and novel-structured catalyst (Ru-(Ni/Fe)C2O4). Experimental and theoretical analyses showed that Ru-(Ni/Fe)C2O4 exhibited extraordinary activities for HER, OER, and HzOR due to the synergistic effect between Ru nanospecies and high-index facets. The electrolyzer assembled with this catalyst achieved a cell voltage reduction to 0.01 V at 10 mA cm-2 for HER-HzOR coupling seawater splitting and remained stable under 500 mA cm-2 at 80 degrees C for 50 hours, approaching the requirements for quasi-industrial electrolysis. This work provides a guideline for preparing multifunctional electrocatalysts and offers an effective strategy for developing seawater electrolysis for a hydrogen economy society.