HOR on Au@PtNi surfaces in alkaline media has been investigated by in situ surface‐enhanced Raman spectroscopy (see picture). Direct spectroscopic evidence for OHad species was observed and further confirmed by deuterium isotopic experiments and DFT.
Abstract
Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange‐membrane fuel cells. However, uncertainty remains around the alkaline HOR mechanism owing to a lack of direct in situ evidence of intermediates. In this study, in situ electrochemical surface‐enhanced Raman spectroscopy (SERS) and DFT were used to study HOR processes on PtNi alloy and Pt surfaces, respectively. Spectroscopic evidence indicates that adsorbed hydroxy species (OHad) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OHad species were not observed on the Pt surface during the HOR. We show that Ni doping promoted hydroxy adsorption on the platinum‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxy adsorption. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.
https://ift.tt/3gTpOuJ
I'm running a preliminary experiment for a project in which I'm testing the adsorption capacity of a novel nonwoven fabric (in an air filtration context).
For this experiment, I'm using material from a face mask (the blue ones that you've seen everywhere this year), and I realized that the fabric is very hydrophobic. My plan was to wash/soak the material using 3% boric acid to capture the adsorbed ammonia, but I'm not sure if that will work, since there's very little direct contact between the liquid and the fabric surface.
I'm considering using a nonpolar solvent to wash the fabric, and then extracting the ammonia using DI water or boric acid, but I'm not sure if a nonpolar solvent can effectively capture ammonia. I've also considered DCM, since I found a paper that reports decent ammonia solubility in DCM, but it's still polar, so it might face the same issues as an aqueous solution.
Any suggestions?
An axial traction strategy is presented to reduce the energy barrier of the dynamic activation process over the M‐N4 structure for boosting CO2RR activity.
Abstract
Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M‐N4) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M‐N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni‐N4‐O/C). The Ni‐N4‐O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) close to 100 % at −0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from −0.5 to −1.1 V. The superior CO2RR activity is due to the Ni‐N4‐O active moiety composed of a Ni‐N4 site with an additional oxygen atom that induces an axial traction effect.
https://ift.tt/2IJd1yp
just took a dose and threw up 5 mins later. should i redose or do you think all the good stuff was adsorbed mostly?
Nature Chemistry, Published online: 18 January 2021; doi:10.1038/s41557-020-00612-y
Recent experiments reporting the isomerization of CO on a NaCl(100) surface—from C adsorbed to O adsorbed—represent a major challenge to simulate from first principles. Now, using dynamics calculations and (CO–NaCl)n cluster models that feature CO–CO interactions, it is found that isomerization occurs via a ‘roaming’ mechanism at a large distance from the NaCl(100) surface.
https://ift.tt/35TUmZ1
What just happened?
The actual role of chalcogens in transition metal chalcogenides as oxygen evolution reaction electrocatalysts is ambiguous. We found the surface‐adsorbed selenates and sulfates, either from in situ oxidation of transition metal chalcogenides or extra addition, played vital roles in the electrochemical oxygen evolution reaction. These results open up new paradigms for the development of adsorption‐modulated efficient electrocatalysts.
Abstract
Transition metal chalcogenides (TMCs) are efficient oxygen evolution reaction (OER) pre‐electrocatalysts, and will in situ transform into metal (oxy)hydroxides under OER condition. However, the role of chalcogen is not fully elucidated after oxidation and severe leaching. Here we present the vital promotion of surface‐adsorbed chalcogenates on the OER activity. Taking NiSe2 as an example, in situ Raman spectroscopy revealed the oxidation of Se‐Se to selenites (SeO32−) then to selenates (SeO42−). Combining the severe Se leaching and the strong signal of selenates, it is assumed that the selenates are rich on the surface and play significant roles. As expected, adding selenites to the electrolyte of Ni(OH)2 dramatically enhance its OER activity. And sulfates also exhibit the similar effect, suggesting the promotion of surface‐adsorbed chalcogenates on OER is universal. Our findings offer unique insight into the transformation mechanism of materials during electrolysis.
https://ift.tt/3idRZ7t
The key descriptor that dominates the kinetics of alkaline hydrogen evolution reaction (HER) has not yet fully been identified so far. Herein, we isolate adsorption hydroxyl (OHad) transfer process (OHad + e– ↔ OH–) and reveal its crucial role in promoting the overall kinetics of alkaline HER based on Ni/Co modified MoSe2 model catalysts (Ni‐MoSe2 and Co‐MoSe2) that feature almost identical water dissociation and hydrogen adsorption energies, but evidently different activity trends in alkaline (Ni‐MoSe2 >> Co‐MoSe2) and acidic (Co‐MoSe2 ≥ Ni‐MoSe2) media. Experimental and theoretical calculation results demonstrate that tailoring MoSe2 with Ni not only optimizes the adsorption of OHad, but also promotes the desorption of OH– and the electron‐involved conversion of OHad to OH–, all of which synergistically accelerate the kinetics of OHad + e– ↔ OH– and thereby the overall kinetics of the alkaline HER. The successful isolating and deeper understanding of OHad + e– ↔ OH– as the critical descriptor of the alkaline HER, shed a new light for designing highly efficient alkaline HER catalysts.
https://ift.tt/2ArN1Dg
Nature Chemistry, Published online: 20 April 2020; doi:10.1038/s41557-020-0453-0
The photoinduced dimerization of a prochiral anthracenecarboxylic acid occurs in an enantioselective fashion when the molecules are adsorbed on helical metal nanostructures. This enantiopreference arises mostly from the helicity of the silver and copper substrates—prepared using shear forces during the deposition process—and may also be influenced by chiroplasmonic effects.
https://ift.tt/2XPa2cN
Nature Chemistry, Published online: 28 September 2020; doi:10.1038/s41557-020-0548-7
Efficient and stable water oxidation catalysts are important if photoelectrochemical cells are to be used to provide clean and sustainable solar fuels. A water oxidation catalyst that operates at neutral pH has now been developed that features ruthenium coordination oligomers anchored onto the surfaces of graphitic materials through CH–π interactions.
https://ift.tt/2EFlhgO
Hi! I am a newbie in DFT, just started research as a first year grad student. I am trying to study a reaction pathway of big molecules such as benzene or Soman on a surface. Problem is, with such huge molecule size, I know entropy will be huge and must be accounted both in gas phase and adsorbed phase. I am looking to do the calculation traditionally via stat thermo, however I was wondering if it is possible to obtain such information via DFT? I am a VASP user by the way. Any help would be much appreciated!
Thank you!
I had this little Theory for a while, the idea as the title says, is that Fazbear Ent only invented Freddy Fazbear and the Puppet,all the others from the main crew were actually mascots and characters adsorbed from other locations that Fazbear brought out over the years, its why when they went under there was no others people to compete with them (as SL mentions,the stage was set for a new Animatronic mascot business.)
The first murder minigame we see in fnaf 2 is actually not showing us Fredbear,but instead the very first Fazbear Location, a Brown Bear with a Cup Cake and his Puppet Friend. Despite the tragedy Fazbear began to grow and expand eventually managing to buy out some unnamed Chica Location (party world maybe?) from this place they now have the IP for Chica and maybe a few others (BB,JJ we don't know).
Along with this they managed to grab some Pirate themed place grabbing the rights to,as we can assume Foxy and maybe some others.
Finally Fredbear Family diner and in the Process coming into possession of the Golden Bonnie and Fredbear IPs, at this point they let these locations still run under their own name,under the title of Fredbear and Freinds,Chica party world and so on.
Then the Springlock Incidents occur,or the bite its somewhat unimportant, this count as the first major financial blow to Fazbear and at this point,they decide to Concept Unify,bring all locations under the Fazbear pizza name,with a brand new Mascot band, a mix of all their IP into one, they Give Chica Freddy's Cupcake,they drop the Golden Colour and redesign Bonnie to be Blue and they give foxy his own dedicated Pirate Space, one mascot from each brand they owned,all as one now.
This is unveiled as Freddy Fazbear Pizza and this is the very first introduction of the Withered Animatronics along with the Fazbear crew as a whole.
It may explain why Foxy is a pirate out of Left Field and why the First murder minigame has a Brown Bear when its allegedly Fredbears diner, it would also be a neat way to open up some more stories and give other character the focus (Ie what happened to the Chica Location and Foxy Location to cause them to sell their brand).
Out of curiosity. I'm looking for a rough estimate on how much water is adsorbed on something like a 100 mL round bottom flask in a standard lab environment (25C low humidity). The flask hasn't been dried in an oven.
Would it be like a few milimols of water...several mols of water...etc?
This isn't about something that happened to me but about something my boss did to others.
So my boss does not exactly work at our office, but he does come from time to time. He knows there's a lot of smokers at the office, lately they've stopped smoking, my boss is a smoker as well.
He was also told about how people in my office were making an effort to stop. So what does he do? He comes in, starts smoking and then tells them all to join him. In part it's their fault, because they are weak and can't stop but he also knew. HE KNEW! He could have smoked elsewhere, not let them see him, not invite them into it. But he doesn't care does he? He doesn't care and he wanted them out there smoking with him, because he's a self adsorbed dick who only wants everyone else at his level so he doesn't have to feel lonely. He's always looking to be the center of attention.
I don't understand how someone can be such an asshole. If he were just asking for attention then he'd just be an annoying fool, but to get all the former smokers back to smoking again? Just to satisfy his fucking shit ego? What an asshole. Those cigarettes they smoked because of him, they could be what sets off lung cancer. Has he not considered that?
I am amazed at how fucking self centered, inhumane and indifferent some people can be. ALL HE HAD TO DO WAS SMOKE ON HIS OWN, FAR AWAY FROM ANYONE ELSE.
I was thinking whether they have this type of fabric yet. But after reading a chemistry stack exchange post on it, activated carbon seems to be the option but it ain't healthy to put it in a mask form right?
Textile experts or chemistry experts in general, please help me out here.
I have heard both descriptions. I think the "same direction" idea comes from defraction.
An axial traction strategy is presented to reduce the energy barrier of the dynamic activation process over the M‐N4 structure for boosting CO2RR activity.
Abstract
Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M‐N4) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M‐N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni‐N4‐O/C). The Ni‐N4‐O/C electrocatalyst exhibited excellent CO2RR performance with a maximum CO Faradic efficiency (FE) close to 100 % at −0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from −0.5 to −1.1 V. The superior CO2RR activity is due to the Ni‐N4‐O active moiety composed of a Ni‐N4 site with an additional oxygen atom that induces an axial traction effect.
https://ift.tt/2IJd1yp
Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange membrane fuel cells (AEMFCs). However, uncertainty remains around the alkaline HOR mechanism due to a lack of direct in situ evidence of the reaction intermediates. Herein, in situ electrochemical surface‐enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations were used to study HOR processes on both PtNi alloy and pure Pt surfaces. Spectroscopic evidence indicates that adsorbed hydroxyl species (OH ad ) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OH ad species were not observed on the surface of pure Pt during the HOR. We show that Ni doping promoted hydroxyl adsorption on the Pt‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxyl adsorption. Thus, we provide direct evidence of the presence of the OH ad intermediate species on an oxophilic metal surface during the HOR and deduce its important role in improving the HOR activity and rate. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.
https://ift.tt/3gTpOuJ
Transition metal chalcogenides (TMCs) are efficient oxygen evolution reaction (OER) pre‐electrocatalysts, and will in situ transform into metal oxyhydroxides under OER condition. However, the role of chalcogen is not fully elucidated after oxidation and severe leaching. Here we present the vital promotion of surface‐adsorbed chalcogenates on the OER activity. Taking NiSe 2 as an example, in situ Raman spectroscopy revealed the oxidation of Se‐Se to selenites (SeO 3 2‐ ) then to selenates (SeO 4 2‐ ). Combining the severe Se leaching and the strong signal of selenates, it is assumed that the selenates are rich on the surface and play significant roles. As expected, adding selenites to the electrolyte of Ni(OH) 2 dramatically enhance the OER activity. And sulfates also exhibit the similar effect, suggesting the promotion of surface‐adsorbed chalcogenates on OER is universal. Our findings offer unique insight into the transformation mechanism of materials during electrolysis.
https://ift.tt/3idRZ7t
Focussing on one step : The transfer of adsorbed hydroxyl (OHad + e−⇄ OH−) has been isolated and identified as a critical step in the alkaline hydrogen evolution reaction on Ni/Co‐modified MoSe2 model catalysts.
Abstract
The key descriptor that dominates the kinetics of the alkaline hydrogen evolution reaction (HER) has not yet been unequivocally identified. Herein, we focus on the adsorbed hydroxyl (OHad) transfer process (OHad + e− ⇄ OH−) and reveal its crucial role in promoting the overall kinetics of alkaline HER based on Ni/Co‐modified MoSe2 model catalysts (Ni‐MoSe2 and Co‐MoSe2) that feature almost identical water dissociation and hydrogen adsorption energies, but evidently different activity trends in alkaline (Ni‐MoSe2 ≫ Co‐MoSe2) and acidic (Co‐MoSe2 ≥ Ni‐MoSe2) media. Experimental and theoretical calculation results demonstrate that tailoring MoSe2 with Ni not only optimizes the hydroxyl adsorption, but also promotes the desorption of OH− and the electron‐involved conversion of OHad to OH−, all of which synergistically accelerate the kinetics of OHad + e− ⇄ OH− and thereby the overall kinetics of the alkaline HER.
https://ift.tt/2ArN1Dg
