Unveiling the geometric site dependent activity of spinel Co_(3)O_(4)for electrocatalytic chlorine evolution reaction

Spinel cobalt oxide(Co_(3)O_(4)),consisting of tetrahedral Co^(2+)(CoTd)and octahedral Co^(3+)(CoOh),is considered as promising earth-abundant electrocatalyst for chlorine evolution reaction(CER).Identifying the catalytic contribution of geometric Co site in the electrocatalytic CER plays a pivotal role to precisely modulate electronic configuration of active Co sites to boost CER.Herein,combining density functional theory calculations and experiment results assisted with operando analysis,we found that the Co_(Oh) site acts as the main active site for CER in spinel Co_(3)O_(4),which shows better Cl^(-)adsorption and more moderate intermediate adsorption toward CER than CoTd site,and does not undergo redox transition under CER condition at applied potentials.Guided by above findings,the oxygen vacancies were further introduced into the Co_(3)O_(4) to precisely manipulate the electronic configuration of Co_(Oh) to boost Cl^(-)adsorption and optimize the reaction path of CER and thus to enhance the intrinsic CER activity significantly.Our work figures out the importance of geometric configuration dependent CER activity,shedding light on the rational design of advanced electrocatalysts from geometric configuration optimization at the atomic level.

Facile preparation of hierarchical Ni@Mn-doped NiO hybrids for efficient and durable oxygen evolution reaction

Exploring highly efficient and non-noble-metal-based electrocatalysts for oxygen evolution reaction(OER)is of great importance not only for water splitting but also for rechargeable metal-air batteries and fuel cells.Herein,we describe a simple strategy to prepare hierarchical Ni@Mn-doped Ni O hybrids using flower-like Ni-Mn layered double hydroxides(Ni Mn-LDHs)as a precursor.After calcination at 400℃for an hour under N_(2)atmosphere,the flower-like Ni Mn-LDHs transform to porous microspheres consisting of nanoparticles,in which Ni cores are encapsulated by Mn-doped NiO shells(denoted as Ni@MnNi O-400).Benefiting to this unique porous,core-shell structures and element doping,the as-prepared Ni@Mn-NiO-400 hybrid shows a low overpotential of 178 mV at the current density of 10 mA/cm^(2)and Tafel slope of 52.7 m V/dec in 1 mol/L KOH solution.More significantly,the Ni@Mn-Ni O-400 hybrid also demonstrates superior stability of 98.6%after 50 h continuously testing,much higher than pristine Ni MnLDHs and commercial IrO_(2)catalyst.In addition,theoretical simulation shows that Ni core and Mn doping greatly affect the electronic states and electronic structure of Ni O.As a result,Ni@Mn-doped Ni O hybrid possesses an optimal adsorption activity towards oxygen species than Ni O and undoped Ni@Ni O hybrid.Considering the compositional and structural flexibility of LDHs,this work may offer a simple method to prepare other non-noble metal-based electrocatalysts for OER.