Single-atom catalysts (SACs) have been extensively applied in CO2 reduction reactions (CO2RRs) due to their unique activity/selectivity and maximum atom efficiency. To form and stabilize SACs, ...introducing oxygen vacancies (VO) on metal oxide surfaces is a common strategy. However, there is a lack of studies on whether the single atoms (SAs) can be stably anchored on VO sites under real reaction conditions, which hinders the rational design of SACs for practical usage. Herein, we combine the first-principles calculations and an artificial intelligence approach to high-throughput screen the stability and activity of 3d, 4d, and 5d transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg) SAs on eight defective metal oxide surfaces (ZnO(100), rutile TiO2(110), Co3O4(001), CoO(100), MnO(100), NiO(100), MgO(100), and ZrO2(111)) during the CO2RR. By evaluating the anchor energies of the 232 catalytic systems, 100 kinds of SACs are stably anchored by VO in vacuum, but only 28 of them remain stable with the adsorption of intermediates of the CO2RR (*COOH, *OCHO, *CO, *CHO, and *H). By subgroup discovery analysis, we elucidate that the stability is attributed to the electronegativity and number of outer electrons of SA, the d-band center of metal oxides, and the relative coordination number of the adsorbed species together. In the further analysis of the selectivity and activity for the CO2 conversion to CO, the VO-ZrO2(111)-supported Os SAC is predicted as most promising in electrocatalysis and Ru/VO-ZrO2(111) exhibits excellent catalytic performances in the reverse water-gas shift reaction.
•Successful fabrication of unique 2D/2D hetero-architecture via in-situ assembly method.•Synergistic effects of different roles of sulfur doping in the enhanced photocatalytic performances of SCN and ...TNS/SCN.•Distinct difference in Femi levels via the modulation of sulfur doping was evidenced by DFT calculations.•Distinct difference in Femi levels enhanced the electronic coupling and accelerated the interfacial charge transport.•Mechanisms toward the TC-HCl degradation and S-scheme interfacial charge transports were proposed.
In this study, novel titanate nanosheets/g-C3N4 (TNS/CN) and titanate nanosheets/sulfur-doped g-C3N4 (TNS/SCN) heterojunctions were successfully fabricated by the in-situ assembly for the efficient removal of tetracycline hydrochloride (TC-HCl). TNS/SCN achieved 1.87, 7.89 and 3.27 times increases in photodegradation performance compared to TNS/CN, TNS and SCN, respectively, due to the collaboration of the unique 2D/2D hetero-architecture, synergistic effects of different roles of sulfur doping in SCN and TNS/SCN, and step-scheme interfacial charge transport. The unique 2D/2D hetero-architecture provided numerous convenient nanochannels for charge transport, while sulfur doping introduced the impurity states and defects in SCN, which contributed to the enhanced visible-light absorption and efficient separation of photo-generated carriers. Besides, sulfur doping induced the distinct difference in Fermi levels and enhanced electronic coupling between TNS and SCN as evidenced by density functional theory calculations and X-ray photoelectron spectra, which facilitated the interfacial charge transport in heterojunction. The accelerated interfacial charge transport in TNS/SCN driven by the enhanced internal electric field promoted the efficient separation of photogenerated carriers. TNS/SCN can achieve excellent stability and reusability after four consecutive cycles, over a wide pH range or under coexisting anion conditions. Mechanisms toward the TC-HCl degradation and step-scheme interfacial charge transport were also proposed. This work provides a new strategy to enhance the catalytic performance of step-scheme heterojunction.
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•The controllable amorphization engineering on CoxFey-MOFs has been successfully realized.•The optimized amorphous Co4Fe6-MOF exhibits superior electrocatalytic OER activity.•The ...amorphous structure and the bimetallic synergistic effects could promote the improvement of catalytic OER activity.
Deliberate tailoring of the metal–organic frameworks (MOFs) composition and structure could provide limitless flexibility for the development of highly efficient electrocatalysts toward oxygen evolution reaction (OER). However, the changes in crystallinity of MOFs related to the composition manipulation have seldom been explored for the catalytic OER activity. Herein, we realize the controllable amorphization engineering on CoxFey-MOFs from crystalline to amorphous state by deliberately adjusting the ratio of Co/Fe precursors introduced within the MOFs. While crystalline MOFs are formed with initially dominating the contribution of Co ions, amorphous MOFs are obtained when the amount of Fe ions exceeds 60%. Theoretical findings propose that the defects formation energies of CoxFey-MOFs can be dramatically reduced with the decrease of Co/Fe ratio, which make the long-range disorder structure be readily formed with abundant defects. The disorder structure and the tunable ratio of Co/Fe enable to endow the bimetallic CoxFey-MOFs with abundant active sites and fast charge transfer, thus boosting the catalytic activity towards OER. It is found that the optimized amorphous Co4Fe6-MOF can deliver the current density of 10 mA cm−2 only at a low overpotential of 241 mV with extremely small Tafel slope of 30.1 mV dec-1. The present work enriches the understanding on the crystalline-to-amorphous transformations and sheds light on the way for the applications of amorphous MOFs nanomaterials in water splitting field.
A suitable photocatalyst for overall water splitting has been produced by overcoming the disadvantage of the band structure in bulk BiOCl by reducing the thickness to the quantum scale. The ultrathin ...BiOCl nanosheets with surface/subsurface defects realized the solar‐driven pure water splitting in the absence of any co‐catalysts or sacrificial agent. These surface defects cannot only shift both the valence band and conduction band upwards for band‐gap narrowing but also promote charge‐carrier separation. The amount of defects in the outer layer surface of BiOCl results in an enhancement of carrier density and faster charge transport. First‐principles calculations provide clear evidence that the formation of surface oxygen vacancies is easier for the ultrathin BiOCl nanosheets than for its thicker counterpart. These defects can serve as active sites to effectively adsorb and dissociate H2O molecules, resulting in a significantly improved water‐splitting performance.
Bring a little sun! A suitable photocatalyst for overall water splitting has been produced by overcoming the disadvantage of the band structure in bulk BiOCl by reducing the thickness to the quantum scale. The ultrathin BiOCl nanosheets with surface/subsurface defects realized the solar‐driven pure water splitting in the absence of any co‐catalysts or sacrificial agent (see figure).
Developing cost‐effective and high‐performance catalysts for oxygen evolution reaction (OER) is essential to improve the efficiency of electrochemical conversion devices. Unfortunately, current ...studies greatly depend on empirical exploration and ignore the inherent relationship between electronic structure and catalytic activity, which impedes the rational design of high‐efficiency OER catalysts. Herein, a series of bimetallic Ni‐based metal‐organic frameworks (Ni‐M‐MOFs, M = Fe, Co, Cu, Mn, and Zn) with well‐defined morphology and active sites are selected as the ideal platform to explore the electronic‐structure/catalytic‐activity relationship. By integrating density‐functional theory calculations and experimental measurements, a volcano‐shaped relationship between electronic properties (d‐band center and eg filling) and OER activity is demonstrated, in which the NiFe‐MOF with the optimized energy level and electronic structure situated closer to the volcano summit. It delivers ultra‐low overpotentials of 215 and 297 mV for 10 and 500 mA cm−2, respectively. The identified electronic‐structure/catalytic activity relationship is found to be universal for other Ni‐based MOF catalysts (e.g., Ni‐M‐BDC‐NH2, Ni‐M‐BTC, Ni‐M‐NDC, Ni‐M‐DOBDC, and Ni‐M‐PYDC). This work widens the applicability of d band center and eg filling descriptors to activity prediction of MOF‐based electrocatalysts, providing an insightful perspective to design highly efficient OER catalysts.
This work clearly demonstrates that the identified electronic‐structure/catalytic‐activity relationship can be utilized to comprehend and forecast oxygen evolution reaction activity changes induced by the substitution of transition‐metal heteroatoms (M = Fe, Co, Cu, Mn, and Zn) into Ni‐MOF, providing a general and clear path for a rational design of highly‐active and cost‐effective catalyst.
Transition metal nitrides (TMNs) are affirmed to be an appealing candidate for boosting the performance of lithium–sulfur (Li–S) batteries due to their excellent conductivity, strong interaction with ...sulfur species, and the effective catalytic ability for conversion of polysulfides. However, the traditional bulk TMNs are difficult to achieve large active surface area and fast transport channels for electrons/ions simultaneously. Here, a 2D ultrathin geometry of titanium nitride (TiN) is realized by a facile topochemical conversion strategy, which can not only serve as an interconnected conductive platform but also expose abundant catalytic active sites. The ultrathin TiN nanosheets are coated on a commercial separator, serving as a multifunctional interlayer in Li–S batteries for hindering the polysulfide shuttle effect by strong capture and fast conversion of polysulfides, achieving a high initial capacity of 1357 mAh g−1 at 0.1 C and demonstrating a low capacity decay of only 0.046% per cycle over 1000 cycles at 1 C.
This research presents a free‐standing 2D ultrathin TiN realized via a facile topochemical conversion strategy, for lithium–sulfur batteries as a multifunctional interlayer. Based on the interconnected conductive platform and highly‐exposed catalytic active sites, the ultrathin TiN can effectively hinder the polysulfide shuttle effect by strong capture and fast conversion of polysulfides.
In this work, we report a one-pot strategy to obtain ionic liquid–capped amorphous FexNiy hydroxide nanoclusters (<2 nm) with exceptional population of oxygen vacancies, which exhibits superior ...activity in oxygen evolution reaction (OER).
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In this work, a one-pot strategy is presented to directly synthesize amorphous FexNiy hydroxide nanoclusters (denoted as ANC-FexNiy, <2 nm) with oxygen vacancies induced by ionic liquids. The ANC-FexNiy catalyst presents abundant catalytic sites and high intrinsic conductivity. As such, the optimized ANC-Fe1Ni2 exhibits high activity in oxygen evolution reaction (OER) with a Tafel slope of 39 mV dec–1 and an overpotential of 266 mV at 10 mA cm−2. Notably, the optimized ANC-Fe1Ni2 shows an extraordinarily large mass activity of 3028 A gFeNi–1 at the overpotential of 300 mV, which is ∼24-fold of commercial RuO2 catalyst. The superior activity of these FexNiy hydroxide nanoclusters is ascribed to (i) the amorphous and distorted structure with abundant oxygen vacancies, and (ii) enhanced active site density by downsizing the ANC-FexNiy clusters. This strategy provides a novel route for enhancing OER electrocatalytic performance and highly encouraging for the future application of amorphous metal hydroxides in catalysis.
Development of high‐performance photoinitiator is the key to enhance the printing speed, structure resolution and product quality in 3D laser printing. Here, to improve the printing efficiency of 3D ...laser nanoprinting, we investigate the underlying photochemistry of gold and silver nanocluster initiators under multiphoton laser excitation. Experimental results and DFT calculations reveal the high cleavage probability of the surface S−C bonds in gold and silver nanoclusters which generate multiple radicals. Based on this understanding, we design several alkyl‐thiolated gold nanoclusters and achieve a more than two‐orders‐of‐magnitude enhancement of photoinitiation activity, as well as a significant improvement in printing resolution and fabrication window. Overall, this work for the first time unveils the detailed radical formation pathways of gold and silver nanoclusters under multiphoton activation and substantially improves their photoinitiation sensitivity via surface engineering, which pushes the limit of the printing efficiency of 3D laser lithography.
The high cleavage probability of the surface S−C bonds in gold and silver nanoclusters and the structure–activity relations of the generated radicals are revealed through experiments and DFT calculations. Based on this understanding, we design several alkyl thiolated gold nanoclusters and achieve a two‐to‐three‐orders‐of‐magnitude enhancement of the photoinitiation activity.
Morphological effects of nanoparticles are crucial in many solid-catalyzed chemical transformations. We herein prepared two manganese-ceria solid solutions, well-defined MnCeO
x
nanorods and MnCeO
x
...-nanocubes, exposing preferentially (111) and (100) facets of ceria, respectively. The incorporation of Mn dopant into ceria lattice strongly enhanced the catalytic performance in the NO reduction with CO. MnCeO
x
(111) catalyst outperformed MnCeO
x
(100) counterpart due to its higher population density of oxygen vacancy defects.
In-situ
infrared spectroscopy investigations indicated that the reaction pathway over MnCeO
x
and pristine CeO
2
is similar and that besides the direct pathway, an indirect pathway via adsorbed hyponitrite as an intermediate cannot be ruled out. X-ray photoelectron and Raman spectroscopies as well as first-principles density functional theory (DFT) calculations indicate that the enhanced catalytic performance of MnCeO
x
can be traced back to its “Mn—O
L
(VÖ)—Mn—O
L
(VÖ)—Ce” connectivities. The Mn dopant strongly facilitates the formation of surface oxygen vacancies (VÖ) by liberating surface lattice oxygen (O
L
) via CO* + O
L
→ CO
2
* + VÖ and promotes the reduction of NO, according to NO* + VÖ → N* + O
L
and 2N* → N
2
. The Mn dopant impact on both the adsorption of CO and activation of O
L
reveals that a balance between these two effects is critical for facilitating all reaction steps.
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