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The Zn-1.5MSA/MCM-41 catalyst with 99% C2H2 conversion, and selectivity to CH3CHO was above 70% within 150 h. MSA ligand was added could improve catalyst dispersion. The catalyst aggregation and Zn species loss were the main reasons for the Zn-based catalyst deactivation.

Introduction of surface defects and phase control engineering in the electrocatalytic system of overall water splitting has played a crucial role in significantly enhancing its electrocatalytic activity toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in water splitting, but the relationship between structure and electrocatalysis is still elusive. Herein, we report a solid–liquid method to induce surface reorganization (formation of a chalcogenide layer with rich chalcogenide vacancies) and phase transformation (Co9S8-to-Co3S4) simultaneously on cobalt chalcogenide. Featuring a uniform 2D morphology and the in situ formation of sulfur (S) vacancies, in a 0.1 M KOH solution, it exhibits a low overpotential of 288 mV vs. RHE at 10 mA cm−2, a low Tafel slope of 43.4 mV dec−1, and strong cycling stability (35 h), outperforming commercial RuO2 and most reported OER electrocatalysts. In addition, we also investigate the OER activity of the Co–S–P electrode in 1.0 M KOH solutions. Co0.37S0.38P0.02 NSs only need 257 mV to reach a current density of 10 mA cm−2. Meanwhile, the Tafel slope of Co0.37S0.38P0.02 NSs (44.0 mV dec−1) is lower than those of other recently reported electrocatalysts. Also, it shows high HER electrocatalytic activity in alkaline and acidic solutions. Finally, the Co0.37S0.38P0.02 electrode is used as a cathode and anode simultaneously for overall water splitting, which merely requires a cell voltage of 1.59 V at 10 mA cm−2 with excellent stability (40 h).

Surface ion vacancy engineering at the atomic scale has attracted much attention to efficiently improve the electrocatalytic activity for the hydrogen evolution reaction (HER). Especially, compared with anion vacancies, cation vacancies are more challenging to generate, and studies on the structure–activity relationship of ion vacancy-rich metal oxide catalysts are still lacking. Herein, by means of abundant dangling unsaturated O and Ru vacancies, we report atomically dispersed MoRu pairs (rGO-MoO3−x–MoRu) stabilized with well-coupled graphene and MoO3−x. The atomically dispersed state of MoRu sites is confirmed by both high-angle annular dark-field scanning TEM (HAADF-STEM) and X-ray absorption fine structure (XAFS) measurements. As a result, rGO-MoO3−x–MoRu pairs show outstanding HER performance with very low overpotentials of 20 and 60 mV at 10 mA cm−2 under alkaline and acidic conditions, and maintain steady hydrogen bubble evolution continuously for 35 h. Meanwhile, for HER activity, they exhibit a positive correlation with the amount of oxygen vacancies, resulting in a favorable change in the adsorption behavior of H atoms on their neighboring Mo or Ru atoms.