Optimizing the electronic structure of CoNx via coupling with N-doped carbon for efficient electrochemical hydrogen evolution.

Transition metal nitrides (TMNs) have been regarded as an excellent class of electrocatalysts for hydrogen evolution reaction (HER), but there is still huge room for improvement. In this work, cobalt nitride (CoNx) coupled with N-doped carbon (NC) and supported by nickel foam (NF) is designed as an efficient HER electrocatalyst (NF/CoNx@NC). The introduction of NC can not only optimize the electronic structure of CoNx to boost the intrinsic activity, but also enhance the electronic conductivity and stability of the catalyst. As a result, NF/CoNx@NC exhibits excellent HER performance. On the one hand, it only needs an overpotential of 69 mV to deliver a current density of 20 mA cm-2 in 1.0 mol/L KOH, far better than that of CoNx (182 mV). On the other hand, the electronic conductivity and stability of the catalyst can be significantly enhanced after the introduction of NC. This work has done successful material design with the goal of enhancing the intrinsic activity, electronic conductivity, and stability, which has certain reference and guiding significance for the design of novel transition metal-based electrocatalysts.

2D metal-organic framework-based materials for electrocatalytic, photocatalytic and thermocatalytic applications.

Ultrathin two-dimensional metal-organic frameworks (2D MOFs) have recently attracted extensive interest in various catalytic fields (e.g., electrocatalysis, photocatalysis, thermocatalysis) due to their ultrathin thickness, large surface area, abundant accessible unsaturated active sites and tunable surface properties. Besides tuning the intrinsic properties of pristine 2D MOFs by changing the metal nodes and organic ligands, one of the hot research trends is to develop 2D MOF hybrids and 2D MOF-derived materials with higher stability and conductivity in order to further increase their activity and durability. Here, the synthesis of 2D MOF nanosheets is briefly summarized and discussed. More attention is focused on summaries and discussions about the applications of these 2D MOFs, their hybrids and their derived materials as electrocatalysts, photocatalysts and thermocatalysts. The superior properties and catalytic performance of these 2D MOF-based catalysts compared to their 3D MOF counterparts in electrocatalysis, photocatalysis and thermocatalysis are highlighted. The enhanced activities of 2D MOFs, their hybrids and derivatives come from abundant accessible active sites, a high density of unsaturated metal nodes, ultrathin thickness, and tunable microenvironments around the MOFs. Views regarding current and future challenges in the field, and new advances in science and technology to meet these challenges, are also presented. Finally, conclusions and outlooks in this field are provided.