Tuning electronic structure of Ni_(3)S_(2) with tungsten doping for high-performance electrooxidation of 5-hydroxymethylfurfural

Electrooxidation of the biomass derivative 5-hydroxymethylfurfural (HMF) is a highly promising approach for attaining versatile value-added chemicals (e.g.,2,5-furandicarboxylic acid,FDCA).Ni-based sulfides are promising electrocatalysts for HMF electrooxidation reaction (HMFOR).However,the HMFOR activity of Ni-based catalysts is far from satisfactory due to the unfavorable adsorption of HMF and OH^(*).Herein,we propose controlled W doping to effectively modify the electronic configuration of nanostructured Ni_(3)S_(2) to manipulate adsorption of HMF and OH^(*),for efficiently converting HMF into FDCA.Experimental and theoretical calculations indicate the incorporation of high-valence W results in the upshift of d-band center of Ni_(3)S_(2),which facilitates the adsorption and dissociation of water to produce more OH^(*).Meanwhile,the high-valence W has strong electron-withdrawing ability and attracts electrons from Ni,leading to the elevated Ni valence,which is beneficial to optimizing the adsorption energy of HMF.Both concurrently contribute to the superb HMFOR performance.As a result,W_(20)-Ni_(3)S_(2)@NF with optimal W dopant exhibits a low driving potential (1.34 V vs.RHE at 10 mA cm^(-2)),accompanying with the 100% HMF conversion,99.2%FDCA selectivity,and 97.3%Faraday efficiency.This work provides a design principle for HMFOR electrocatalysts by modulating the adsorption behaviors of HMF and OH^(*)via rational electronic structure engineering.

Insight into the growth behaviors of MoS_(2)nanograins influenced by step edges and atomic structure of the substrate

The step edges and intrinsic atomic structure of single-crystal substrate play a critical role in determining the growth pathways of transition metal dichalcogenide(TMD)grains,particularly whether the TMDs will grow into wafer-scale single-crystal or anisotropic nanoribbons.Hereby,we investigate the growth behaviours of the MoS_(2)nanograins on(0001)and()sapphire substrates.On one hand,the step edges formed on the(0001)surface after thermal treatment are found to promote the macroscopic aggregation of MoS_(2)nanograins and to form unidirectional large triangular islands along with the<>steps in the annealing process,while on the pristine(0001)surface,the MoS_(2)nanograins grow into a random network-like pattern.Moreover,oxygen treatment on the substrate can further enhance the growth of MoS_(2)nanograins.Transmission electron microscopy and fast Fourier transform patterns reveal that the substrate could modulate the orientation of MoS_(2)nanograins during their growing process.On the other hand,the MoS_(2)nanograins on the surface could self-assemble into one-dimensional nanoribbons due to the strong structural anisotropy of the substrate.In addition,the ratio of Raman intensities for peaks that correspond to the and A1g phonon modes shows a linear relationship with the grain size due to the change of the“phonon confinement”.Moreover,new peaks located at 226 and 280 cm−1 can be observed in the off-resonant and resonant Raman spectra for the MoS_(2)nanograin samples,respectively,which can be attributed to the scatterings from the edges of as-fabricated MoS_(2)nanostructures.