Tunable Atomic-Scale Steps and Cavities Break Both Stability and Activity Limits of CoO_(x) Nanosheets to Catalyze Oxygen Evolution

A highly active interface can enhance the catalytic efficiency of catalysts toward the oxygen evolution reaction(OER).However,accurately tuning their atomic interface configurations of defects with sufficient activity and stability remains a grand challenge.Herein,we report on breaking the activity and stability limits of CoO_(x) nanosheets in the OER process by constructing copious high-energy atomic steps and cavities,in which S or Ce atoms simultaneously replace O or Co atoms from CoO_(x),thus achieving high-energy atomic interface Ce,O-Co_(3)S_(4) nanosheets.By combining in situ characterization and density functional theory calculations,it is shown that the unique orbital coupling between Ce-4f,O(S)-2p,and Co-3d causes it to be closer to the Fermi level,leading to faster charge transfer capability.More importantly,the novel structure breaks the stability limit of cobalt sulfide with planar defects,which gives high catalytic activity and stability in 0.1 M KOH solutions,better than commercial RuO_(2) and IrO_(2) noble metal catalysts.As expected,Ce,O-Co_(3)S_(4) possesses much better turnover frequency activity(0.064 s^(-1))at an overpotential of 300 mV,which is ~7 times larger than that of Ce-CoO_(x)(0.009 s^(-1)).Our work presents a new perspective of designing catalysts with atomically dispersed orbital electronic coupling defects toward efficient OER electrocatalysis.

Effects of sulfate-reducing bacteria on methylmercury at the sediment–water interface

Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.