Regulating the frontier orbital of iron phthalocyanine with nitrogen doped carbon nanosheets for improving oxygen reduction activity.

Iron phthalocyanine (FePc) has attracted widespread attention for its tunable electronic structure. However, the Fe-N sites suffer from undesirable oxygen reduction activity due to the symmetric geometries. A suitable substrate was thus needed to induce electron redistribution around Fe-N to improve the activity. Herein, ultrathin nitrogen-doped carbon nanosheets (N-CNSs) were prepared by a simple high temperature pyrolysis. Then iron phthalocyanine was loaded on the ultrathin nitrogen-doped carbon nanosheets (FePc@N-CNSs) by a low-cost and simple solution method. This composite catalyst shows an excellent ORR activity with a half potential of 0.88 V, an onset potential of 0.99 V and durability superior to commercial Pt/C. When used as an air cathode catalyst for rechargeable zinc-air batteries, FePc@N-CNS modified batteries outperform Pt/C + RuO2 modified batteries with higher power density and superior constant current charge-discharge cycling stability of 37 hours. The regulated electronic structure of FePc by the N-CNS substrate was revealed further by DFT calculations, which explained the enhanced adsorption of the active center to the intermediates and the increased ORR performance.

Fundamental understanding of electrocatalysis over layered double hydroxides from the aspects of crystal and electronic structures.

Layered double hydroxides (LDHs) composed of octahedral ligand units centered with various transition metal atoms display unique electronic structures and thus attract significant attention in the field of electrocatalytic oxygen evolution reactions (OER). Intensive experimental explorations have therefore been carried out to investigate the LDHs synthesis, amorphous control, intrinsic material modifications, interfacing with other phases, strain, etc. There is still the need for a fundamental understanding of the structure-property relations, which could hinder the design of the next generation of the LDHs catalysts. In this review, we firstly provide the crystal structure information accompanied by the corresponding electronic structures. Then, we discuss the conflicts of the active sites on the NiFe LDHs and propose the synergistic cooperation among the ligand units during OER to deliver a different angle for understanding the current structure-property relations beyond the single-site-based catalysis process. In the next section of the OER process, the linear relationship-induced theoretical limit of the overpotential is further discussed based on the fundamental aspects. To break up the linear relations, we have summarized the current strategies for optimizing the OER performance. Lastly, based on the understanding gained above, the perspective of the research challenges and opportunities are proposed.

Surface vacancy on PtTe2 for promoting CO oxidation through efficiently activating O2.

Platinum group metal dichalcogenides (PtTe2) with controllable thickness have been synthesized and confirmed to be promising electric and spintronic materials. Here, using the first-principles calculations, we demonstrate the potential application of PtTe2 as catalyst substrate. Taking CO oxidation as model reaction, the importance of surface vacancy is clarified. It is found that surface vacancy on PtTe2 could improve the stability and catalytic activity of the supported Pt atom. The details of CO oxidation processes indicate that surface vacancy could weaken the adsorption of reactants and speed up the formation and decomposition of OOCO intermediate on Pt catalysts. The underlying mechanisms for the improved activity are unveiled through comprehensively analyzing the charge transfer, density of states, and charge density difference. We hope that the current findings were beneficial for the research and development of efficient catalysts by collocating various single atom/cluster catalysts with different platinum group metal dichalcogenides.