Theoretical Investigation of HER and OER Electrocatalysts Based on the 2D R-graphyne Completely Composed of Anti-Aromatic Carbon Rings

Based on the DFT calculations, two-dimensional (2D) R-graphyne has been demonstrated to have high stability and good conductivity, which can be conducive to the relevant electrocatalytic activity of the material. Different from the poor graphene, R-graphyne, which is completely composed of anti-aromatic structural units, can exhibit certain HER catalytic activity. In addition, doping the TM atoms in Group VIIIB can be considered an effective strategy to enhance the HER catalytic activity of R-graphyne. Particularly, Fe@R-graphyne, Os@R-graphyne, Rh@R-graphyne and Ir@R-graphyne can exhibit higher HER catalytic activities due to the formation of more active sites. Usually, the shorter the distance between the TM and C atoms is, the better the HER activity of the C-site is. Furthermore, doping Ni and Rh atoms of Group VIIIB can significantly improve the OER catalytic performance of R-graphyne. It can be found that ΔG_O* can be used as a good descriptor for the OER activities of TM@R-graphyne systems. Both Rh@R-graphyne and Ni@R-graphyne systems can exhibit bifunctional electrocatalytic activities for HER/OER. In addition, all the relevant catalytic mechanisms are analyzed in detail. This work not only provides nonprecious and highly efficient HER/OER electrocatalysts, but also provides new ideas for the design of carbon-based electrocatalysts.

Insight into electrocatalytic activity and mechanism of bimetal niobium-based oxides in situ embedded into biomass-derived porous carbon skeleton nanohybrids for photovoltaics and alkaline hydrogen evolution

Developing highly-efficient multifunctional electrocatalysts for energy conversion devices is of great importance. A sequence of nano-sized bimetal (Al, Cr, Fe) niobium oxide nanoparticles anchored on aloe peel-derived porous carbon skeleton hybrids (AN/APPC, CN/APPC, and FN/APPC) are successfully prepared via co-precipitation avenue and used as electrocatalysts for photovoltaics and alkaline hydrogen evolution reaction. Benefiting from the synergies between nano-sized metal niobium oxides and highly conductive porous carbon skeleton, these robust polycomponent hybrid electrocatalysts exhibit superior catalytic performances for accelerating the triiodide reduction and hydrogen evolution reaction. The solar cell with AN/APPC electrocatalyst achieves an outstanding device efficiency of 7.31%, superior to that with Pt (6.84%), and the AN/APPC electrocatalyst exhibit an overpotential (131.6 mV) when the current density is 10 mA cm^-2 and Tafel slope (54 mV dec^-1) in 1 M KOH for hydrogen evolution reaction. The AN/APPC electrocatalysts illustrate remarkable electrochemical durability in both I₃^-/I^- electrolyte and alkaline media. Furthermore, the catalytic mechanism was clarified both from the electronic structure and work function through first-principle density functional theory (DFT) calculations. This work opens a new avenue for electrocatalysis field via using nano-sized porous bio-carbon skeleton loaded with niobium-based binary metal.

Highly active metal-free hetero-nanotube catalysts for the hydrogen evolution reaction

The development of low-cost, high-efficiency catalysts for the hydrogen evolution reaction is important for hydrogen production. In this study we investigate hydrogen adsorption at the interfaces of C/BN hetero-nanotubes using first-principles density functional theory calculations. Substantial charge redistributions associated with states near the Fermi level occur at the interfaces. More importantly, such electronic modification can enhance hydrogen adsorption at the interfacial atoms. As a result, the adsorption free energies ΔG_H*of hydrogen for the interfaces range from -0.26 to 0.30 eV, depending on hydrogen coverage. These values are much closer to zero than those for the basal plane, suggesting that the interfaces could be active sites for the hydrogen evolution reaction. The interfacial adsorption sites show a distinctive hybridization between the H s and C p orbitals, which accounts for the enhanced hydrogen adsorption at the interfaces. These findings have important implications for hydrogen energy applications.

Simultaneous catalytic reduction of p-nitrophenol and hydrogen production on MIL-101(Fe)-based composites

MIL-101(Fe)-based composite materials and their application for the generation of H₂ by the catalytic reduction of nitro organics are reported in this study.

P- or S-Doped graphdiyne as a superior metal-free electrocatalyst for the hydrogen evolution reaction: a computational study

By carefully controlling the type and site of the P or S dopant, graphdiyne can be utilized as a promising electrocatalyst with high efficiency for the hydrogen evolution reaction.

Hydrogen evolution reaction at the interfaces of two-dimensional lateral heterostructures: a first-principles study

Owing to the synergetic effects of different two-dimensional (2D) materials, 2D heterostructures have recently attracted much attention in the field of catalysis. We present a first-principles study of hydrogen adsorption on the lateral heterostructure of graphene and h-BN, and its potential application in the hydrogen evolution reaction. The density functional theory calculations in this study show that substantial charge transfer occurs at the heterostructure interfaces, which can enhance the H adsorption on the interfacial atoms. Consequently, the adsorption free energy ΔG H* of the interfaces becomes close to zero, which is optimal for the hydrogen evolution reaction. The results also demonstrate that ΔG H* decreases monotonically with increase in the p-band center, indicating that s-p hybridization plays a crucial role in determining the adsorption strength. These findings are expected to be broadly applicable to other 2D lateral heterostructures, providing a new strategy for hydrogen production.

Embedding tetrahedral 3d transition metal TM4 clusters into the cavity of two-dimensional graphdiyne to construct highly efficient and nonprecious electrocatalysts for hydrogen evolution reaction

Coupled with the high structural stability and good conductivity, all the new 2D composite nanostructures TM₄@GDY (TM = Sc, Ti, Mn, Fe, Co, Ni and Cu) can uniformly exhibit considerably high catalytic activity for hydrogen evolution reaction.

Applying surface strain and coupling with pure or N/B-doped graphene to successfully achieve high HER catalytic activity in 2D layered SnP3-based nanomaterials: a first-principles investigation

Applying external strain and coupling with pure or N/B-doped graphene can be viewed as effective strategies to further improve the HER activity of 2D layered SnP₃ nanomaterials by optimizing the adsorption state of H* and electronic properties.