Abstract
The renewable-electricity-powered CO
2
electroreduction reaction provides a promising means to store intermittent renewable energy in the form of valuable chemicals and dispatchable fuels. ...Renewable methane produced using CO
2
electroreduction attracts interest due to the established global distribution network; however, present-day efficiencies and activities remain below those required for practical application. Here we exploit the fact that the suppression of *CO dimerization and hydrogen evolution promotes methane selectivity: we reason that the introduction of Au in Cu favors *CO protonation vs. C−C coupling under low *CO coverage and weakens the *H adsorption energy of the surface, leading to a reduction in hydrogen evolution. We construct experimentally a suite of Au-Cu catalysts and control *CO availability by regulating CO
2
concentration and reaction rate. This strategy leads to a 1.6× improvement in the methane:H
2
selectivity ratio compared to the best prior reports operating above 100 mA cm
−2
. We as a result achieve a CO
2
-to-methane Faradaic efficiency (FE) of (56 ± 2)% at a production rate of (112 ± 4) mA cm
−2
.
Metal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. ...Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm
in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm
. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C
H
electrosynthesis at current density 200 mA/cm
for over 80 h.
Abstract
Performing CO
2
reduction in acidic conditions enables high single-pass CO
2
conversion efficiency. However, a faster kinetics of the hydrogen evolution reaction compared to CO
2
reduction ...limits the selectivity toward multicarbon products. Prior studies have shown that adsorbed hydroxide on the Cu surface promotes CO
2
reduction in neutral and alkaline conditions. We posited that limited adsorbed hydroxide species in acidic CO
2
reduction could contribute to a low selectivity to multicarbon products. Here we report an electrodeposited Cu catalyst that suppresses hydrogen formation and promotes selective CO
2
reduction in acidic conditions. Using in situ time-resolved Raman spectroscopy, we show that a high concentration of CO and OH on the catalyst surface promotes C-C coupling, a finding that we correlate with evidence of increased CO residence time. The optimized electrodeposited Cu catalyst achieves a 60% faradaic efficiency for ethylene and 90% for multicarbon products. When deployed in a slim flow cell, the catalyst attains a 20% energy efficiency to ethylene, and 30% to multicarbon products.
Density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations were performed to understand graphene and its interaction with polycyclic aromatic hydrocarbons (PAHs) ...molecules. The adsorption energy was predicted to increase with the number of aromatic rings in the adsorbates, and linearly correlate with the hydrophobicity of PAHs. Additionally, the analysis of the electronic properties showed that PAHs behave as mild n-dopants and introduce electrons into graphene; but do not remarkably modify the band gap of graphene, indicating that the interaction between PAHs and graphene is physisorption. We have also discovered highly sensitive strain dependence on the adsorption strength of PAHs onto graphene surface. The AIMD simulation indicated that a sensitive and fast adsorption process of PAHs can be achieved by choosing graphene as the adsorbent. These findings are anticipated to shed light on the future development of graphene-based materials with potential applications in the capture and removal of persistent aromatic pollutants.
The Sabatier principle is widely explored in heterogeneous catalysis, graphically depicted in volcano plots. The most desirable activity is located at the peak of the volcano, and further advances in ...activity past this optimum are possible by designing a catalyst that circumvents the limitation entailed by the Sabatier principle. Herein, by density functional theory calculations, we discovered an unusual Sabatier principle on high entropy alloy (HEA) surface, distinguishing the "just right" (ΔG
= 0 eV) in the Sabatier principle of hydrogen evolution reaction (HER). A new descriptor was proposed to design HEA catalysts for HER. As a proof-of-concept, the synthesized PtFeCoNiCu HEA catalyst endows a high catalytic performance for HER with an overpotential of 10.8 mV at -10 mA cm
and 4.6 times higher intrinsic activity over the state-of-the-art Pt/C. Moreover, the unusual Sabatier principle on HEA catalysts can be extended to other catalytic reactions.
In this work, combined techniques were utilized to interpret the catalytic mechanism of Ag+ ions in sulfuric acid-ferric sulfate system of chalcopyrite. Density functional theory (DFT) calculations ...indicated the favorable adsorption of Ag+ ions on reconstructed (001)-S and (112)-S surfaces of chalcopyrite, and confirmed the possibility of silver sulfide and sulfur vacancy formations. XPS analysis further indicated the formation of silver sulfide on chalcopyrite surface. Electrochemical analysis showed that silver catalyzed chalcopyrite dissolution by enhancing the electrochemical reactivity. In addition, the incorporation of silver atoms into the chalcopyrite surface might cause a major distortion in its structure and accelerated the diffusion rate of copper atoms mainly because of that the Cu+ ionic radius is much smaller than that of Ag+. As a consequence, the accumulation of passivating species was prevented and the adverse effect of passivation layer mainly consisting of polysulfide and metallic oxides was reduced, thus resulting in high dissolution kinetics. According to the present work, a model for interpreting catalytic mechanisms of Ag+ in chalcopyrite dissolution is provided.
•The adsorption of Ag+ on (001)-S and (112)-S chalcopyrite surface was studied.•The reaction energetics of Ag+ with (001)-S and (112)-S surfaces were studied.•The interaction between chalcopyrite surface and Ag+ formed silver sulfide.•Incorporation of Ag caused structure distortion and enhanced Cu diffusion process.•Ag reduced passivating species formation by enhancing electrochemical reactivity.
Abstract
Electrochemical CO
2
reduction (CO
2
R) is an approach to closing the carbon cycle for chemical synthesis. To date, the field has focused on the electrolysis of ambient pressure CO
2
. ...However, industrial CO
2
is pressurized—in capture, transport and storage—and is often in dissolved form. Here, we find that pressurization to 50 bar steers CO
2
R pathways toward formate, something seen across widely-employed CO
2
R catalysts. By developing
operando
methods compatible with high pressures, including quantitative
operando
Raman spectroscopy, we link the high formate selectivity to increased CO
2
coverage on the cathode surface. The interplay of theory and experiments validates the mechanism, and guides us to functionalize the surface of a Cu cathode with a proton-resistant layer to further the pressure-mediated selectivity effect. This work illustrates the value of industrial CO
2
sources as the starting feedstock for sustainable chemical synthesis.
Anion exchange membrane fuel cells are limited by the slow kinetics of alkaline hydrogen oxidation reaction (HOR). Here, we establish HOR catalytic activities of single-atom and diatomic sites as a ...function of *H and *OH binding energies to screen the optimal active sites for the HOR. As a result, the Ru-Ni diatomic one is identified as the best active center. Guided by the theoretical finding, we subsequently synthesize a catalyst with Ru-Ni diatomic sites supported on N-doped porous carbon, which exhibits excellent catalytic activity, CO tolerance, and stability for alkaline HOR and is also superior to single-site counterparts. In situ scanning electrochemical microscopy study validates the HOR activity resulting from the Ru-Ni diatomic sites. Furthermore, in situ x-ray absorption spectroscopy and computational studies unveil a synergistic interaction between Ru and Ni to promote the molecular H
dissociation and strengthen OH adsorption at the diatomic sites, and thus enhance the kinetics of HOR.
Abstract
Renewable CH
4
produced from electrocatalytic CO
2
reduction is viewed as a sustainable and versatile energy carrier, compatible with existing infrastructure. However, conventional alkaline ...and neutral CO
2
-to-CH
4
systems suffer CO
2
loss to carbonates, and recovering the lost CO
2
requires input energy exceeding the heating value of the produced CH
4
. Here we pursue CH
4
-selective electrocatalysis in acidic conditions via a coordination method, stabilizing free Cu ions by bonding Cu with multidentate donor sites. We find that hexadentate donor sites in ethylenediaminetetraacetic acid enable the chelation of Cu ions, regulating Cu cluster size and forming Cu-N/O single sites that achieve high CH
4
selectivity in acidic conditions. We report a CH
4
Faradaic efficiency of 71% (at 100 mA cm
−2
) with <3% loss in total input CO
2
that results in an overall energy intensity (254 GJ/tonne CH
4
), half that of existing electroproduction routes.
Atmospheric phase is the main factor affecting the accuracy of ground-based synthetic aperture radar. The atmospheric phase screen (APS) may be very complicated, due to the drastic changes in ...atmospheric conditions, and the conventional correction methods based on regression models cannot fit and correct it effectively. Partition correction is a feasible path to improve atmospheric phase correction (APC) accuracy for complicated APS, but the overfitting problem cannot be ignored. In this article, we propose a clustering partition method, based on the normal vector of APS, which can partition the complicated APS more reasonably, and then perform APC based on the partition results. APC, and simulation experiments on measurement data, suggests that the proposed method achieves higher accuracy than the conventional model-based methods for complicated APS and avoids severe overfitting, realizing the balance between accuracy and credibility. This article verifies the feasibility and effectiveness of using APS distribution information to guide the partition and conduct APC.
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