Lin Tian,Zhenyang Chen,Tingjian Wang,Ming Cao,Xinhua Lu,Wenjing Cheng,Changchun He,Ju Wang,Zhao Li
Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H2O2-assisted etching method is proposed for the fabrication of Mo-doped ultrathin Co9Se8@NiSe/NF-X heterojunctions with rich Se vacancies to boost electrocatalytic water oxidation. After step-by-step electronic structure modulation by Mo doping and Se vacancy engineering, the self-standing Mo-Co9Se8@NiSe/NF-60 heterojunctions deliver a current density of 50 mA cm−2 with an overpotential of 343 mV and a cell voltage of only 1.87 V at 50 mA cm−2 for overall water splitting in 1.0 M KOH. Our study opens up the possibility of realizing step-by-step electronic structure modulation of nonprecious OER electrocatalysts via heteroatom doping and vacancy engineering.
Shuo Wang,Yong Yan,Yongping Du,Yuguo Zhao,Tongxian Li,Dong Wang,Peter Schaaf,Xiayan Wang
Recently, Ni-based chalcogenides havedemonstrated remarkable activity and selectivity for alcohol electrooxidation, but the mechanisms remain debated. This study synthesizes Ni-based electrodeswith different chalcogen anion coordination on nickel nanorod arrays (NiO x /Ni,NiS x /Ni, and NiSe x /Ni NRAs). NiSe x /Ni NRAsshowcases superior performance (Faradaic efficiency 92.9%) in glycerolelectrooxidation reaction (GOR). In situ spectroscopy reveals that NiSecoordination inhibits deep oxidative reconstruction of the Ni-based interface, preventingNiOOH phase formation during GOR, enhancing activity and stability of NiSe x /NiNRAs. Conversely, NiS and NiO coordination lead to deep reconstruction with NiOOHphase formation, limiting GOR performance. Differently, during competingreaction of GOR, the oxygen evolution reaction (OER) leads to deepreconstruction of NiSex interface due to the instability of Ni-Sebonds, inducing performance degradation and dissolution of Se components. Furthermechanism investigation elucidates that the rate-determining step (RDS) ofGOR at the NiSe x interface involves oxidation of *C 2 H 3 O 3 intermediatesthrough H 2 O adsorption, favoring stable formate production.Contrarily, the RDS at the NiS x , NiO x , and NiOOHinterfaces predominantly focus on the decarboxylation of multi-carbon intermediates, raisingenergy barriers and over-oxidizing formate to CO 2 . These results providenew insights for designing Ni-based non-oxide catalysts forefficient and stable electrocatalytic oxidation.
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