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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).

A simple one-pot approach to the in situ construction of ultrathin shells is developed to create a new highly efficient and durable Pt-based electrocatalyst for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, the synthesized ultrathin PdPtAg-shells are located on twinned PdAg nanocrystals and deposited onto graphene (G) (denoted by PdAg@PdPtAg/rGO). The PdAg@PdPtAg/rGO nanocrystal shows a low overpotential of 22 mV at 10 mA cm−2 and excellent electrochemical stability with 99.5% retention over either 12 h or 30 000 cycles of HER. Meanwhile, its ORR activities in acidic and alkaline media are very high and better than that of commercially available Pt/C. Both the experimental and calculated results suggest that the presence of an ultrathin PdPtAg alloy shell synthesized on a PdAg twinned support is the main reason for the greatly enhanced activities. Moreover, the twinned PdAg nanocrystal provides a number of twinned grain boundaries and defect sites (such as step, edge and kink sites). This typical structure represents a new strategy for synthesizing high-performance Pt-based catalysts, promoting their practical applications in energy conversion and storage devices.

Defect engineering is widely applied in transition metal dichalcogenides to produce high-purity hydrogen. However, the instability of vacancy states on catalysis still remains a considerable challenge. Here, our first-principles calculations showed that, by optimizing the asymmetric S vacancy in the highly asymmetric 1T' crystal of layered bitransition metal dichalcogenides (Co-MoS2) in light of Pd modulation, the relative amount of metastable phase and the quantity of active sites in the structure can be reduced and increased, respectively, leading to a further boosted hydrogen evolution reaction (HER) activity toward layered bi-transition metal dichalcogenides. Thus, we then used a "click" chemistry strategy to make such a catalyst with engineered unsaturated sulfur edges via a strong coupling effect between ultrafine Pd ensembles and Co-MoS2 nanosheets. As expected, the Pd-modulated Co-MoS2 nanosheets exhibited a very low overpotential of 60 mV at 10 mA cm-2 with a small Tafel slope (56 mV dec-1) for the HER in 1.0 M PBS, comparable to those of commercial Pt/C. In addition, their high HER activity was retained in acidic and alkaline conditions. Both the theoretical and experimental results revealed that Pd ensembles can efficiently activate and stabilize the inert basal plane S sites during HER processes as a result of the formation of Pd-S in Co-MoS2. This work not only provides a deeper understanding of the correlation between defect sites and intrinsic HER catalytic properties for transition metal chalcogenide (TMD)-based catalysts, but also offers new insights into better designing earth-abundant HER catalysts displaying high efficiency and durability.

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.

The influence of plasma pretreatment on the catalytic performance of Zn based catalyst in acetylene hydration was studied. Furthermore, the atmosphere (N2, O2, NH3, air) and process conditions (pretreatment time, pretreatment power, gas flow) of plasma pretreatment were investigated systematically. The activity results showed that both the conversion and selectivity of the P-Zn/MCM-41 catalyst treated by oxygen plasma improved significantly. The characterization results suggested that the plasma treated catalyst enhances the mutual effect between the Zn species and MCM-41 carrier, promotes the dispersion of the active component and inhibits the loss of Zn species.