Inspired by natural photosynthesis, Z‐scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal‐free Z‐scheme photocatalysts for overall water ...splitting, however, still remains challenging. The construction of polymer‐based van der Waals heterostructures as metal‐free Z‐scheme photocatalytic systems for overall water splitting is described using aza‐fused microporous polymers (CMP) and C2N ultrathin nanosheets as O2‐ and H2‐evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H2 and O2 was observed when aza‐CMP/C2N heterostructures were used. A solar‐to‐hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge‐transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting.
After all, you're my van der Waal: A metal‐free Z‐scheme photocatalytic system was prepared for efficient overall water splitting. 2D van der Waals heterostructures composed of ultrathin polymer nanosheets facilitate charge separation and consequently enhance the lifetime and density of photogenerated excitons.
Abstract
Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single ...copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S
1
N
3
moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S
1
N
3
moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.
Abstract
The photofixation and utilization of CO
2
via single-electron mechanism is considered to be a clean and green way to produce high-value-added commodity chemicals with long carbon chains. ...However, this topic has not been fully explored for the highly negative reduction potential in the formation of reactive carbonate radical. Herein, by taking Bi
2
O
3
nanosheets as a model system, we illustrate that oxygen vacancies confined in atomic layers can lower the adsorption energy of CO
2
on the reactive sites, and thus activate CO
2
by single-electron transfer in mild conditions. As demonstrated, Bi
2
O
3
nanosheets with rich oxygen vacancies show enhanced generation of •CO
2
–
species during the reaction process and achieve a high conversion yield of dimethyl carbonate (DMC) with nearly 100% selectivity in the presence of methanol. This study establishes a practical way for the photofixation of CO
2
to long-chain chemicals via defect engineering.
Molybdenum disulfide is naturally inert for alkaline hydrogen evolution catalysis, due to its unfavorable water adsorption and dissociation feature originated from the unsuitable orbital orientation. ...Herein, we successfully endow molybdenum disulfide with exceptional alkaline hydrogen evolution capability by carbon-induced orbital modulation. The prepared carbon doped molybdenum disulfide displays an unprecedented overpotential of 45 mV at 10 mA cm
, which is substantially lower than 228 mV of the molybdenum disulfide and also represents the best alkaline hydrogen evolution catalytic activity among the ever-reported molybdenum disulfide catalysts. Fine structural analysis indicates the electronic and coordination structures of molybdenum disulfide have been significantly changed with carbon incorporation. Moreover, theoretical calculation further reveals carbon doping could create empty 2p orbitals perpendicular to the basal plane, enabling energetically favorable water adsorption and dissociation. The concept of orbital modulation could offer a unique approach for the rational design of hydrogen evolution catalysts and beyond.
Abstract
Supported metal nanoclusters consisting of several dozen atoms are highly attractive for heterogeneous catalysis with unique catalytic properties. However, the metal nanocluster catalysts ...face the challenges of thermal sintering and consequent deactivation owing to the loss of metal surface areas particularly in the applications of high-temperature reactions. Here, we report that sulfur—a documented poison reagent for metal catalysts—when doped in a carbon matrix can stabilize ~1 nanometer metal nanoclusters (Pt, Ru, Rh, Os, and Ir) at high temperatures up to 700 °C. We find that the enhanced adhesion strength between metal nanoclusters and the sulfur-doped carbon support, which arises from the interfacial metal-sulfur bonding, greatly retards both metal atom diffusion and nanocluster migration. In catalyzing propane dehydrogenation at 550 °C, the sulfur-doped carbon supported Pt nanocluster catalyst with interfacial electronic effects exhibits higher selectivity to propene as well as more stable durability than sulfur-free carbon supported catalysts.
Abstract
Lithium-sulfur batteries show great potential to achieve high-energy-density storage, but their long-term stability is still limited due to the shuttle effect caused by the dissolution of ...polysulfides into electrolyte. Herein, we report a strategy of significantly improving the polysulfides adsorption capability of cobaltous oxide by amorphization-induced surface electronic states modulation. The amorphous cobaltous oxide nanosheets as the cathode additives for lithium-sulfur batteries demonstrates the rate capability and cycling stability with an initial capacity of 1248.2 mAh g
-1
at 1 C and a substantial capacity retention of 1037.3 mAh g
-1
after 500 cycles. X-ray absorption spectroscopy analysis reveal that the coordination structures and symmetry of ligand field around Co atoms of cobaltous oxide nanosheets are notably changed after amorphization. Moreover, DFT studies further indicate that amorphization-induced re-distribution of
d
orbital makes more electrons occupy high energy level, thereby resulting in a high binding energy with polysulfides for favorable adsorption.
Visible‐light‐driven conversion of CO2 into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be ...both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single‐atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO2 conversion, wherein the graphene bridges homogeneous light absorbers with single‐atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min−1, superior to those obtained with the state‐of‐the‐art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO2 conversion from the angle of single‐atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts.
Single‐atom Co sites coordinated on partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO2 conversion, wherein the graphene bridges homogeneous light absorbers with single‐atom catalytic sites for the efficient transfer of photoexcited electrons. This design enables a turnover frequency of 3.77 min−1, superior to those obtained with conventional heterogeneous photocatalysts.
Isolated single atomic site catalysts have attracted great interest due to their remarkable catalytic properties. Because of their high surface energy, single atoms are highly mobile and tend to form ...aggregate during synthetic and catalytic processes. Therefore, it is a significant challenge to fabricate isolated single atomic site catalysts with good stability. Herein, a gentle method to stabilize single atomic site metal by constructing defects on the surface of supports is presented. As a proof of concept, single atomic site Au supported on defective TiO2 nanosheets is prepared and it is discovered that (1) the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming the Ti–Au–Ti structure; and (2) the Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites. It is believed that this work paves a way to design stable and active single atomic site catalysts on oxide supports.
Single atomic sites of Au are supported on defective TiO2 nanosheets and it is discovered that the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming a Ti–Au–Ti structure, and this Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites.
The oxidation of hydrocarbons to produce high value-added compounds (ketones or alcohols) using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and ...economic views. Herein, we successfully synthesized cobalt single atom site catalysts (Co SACs) with high metal loading of 23.58 wt.% supported on carbon nitride (CN), which showed excellent catalytic properties for oxidation of ethylbenzene in air. Moreover, Co SACs show a much higher turn-over frequency (19.6 h
−1
) than other reported non-noble catalysts under the same condition. Comparatively, the as-obtained nanosized or homogenous Co catalysts are inert to this reaction. Co SACs also exhibit high selectivity (97%) and stability (unchanged after five runs) in this reaction. DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water, which result in the robust catalytic performance for this reaction.
Abstract
As a promising hydrogen carrier, formic acid (HCOOH) is renewable, safe and nontoxic. Although noble-metal-based catalysts have exhibited excellent activity in HCOOH dehydrogenation, ...developing non-noble-metal heterogeneous catalysts with high efficiency remains a great challenge. Here, we modulate oxygen coverage on the surface of Ti
3
C
2
T
x
MXenes to boost the catalytic activity toward HCOOH dehydrogenation. Impressively, Ti
3
C
2
T
x
MXenes after treating with air at 250 °C (Ti
3
C
2
T
x
-250) significantly increase the amount of surface oxygen atoms without the change of crystalline structure, exhibiting a mass activity of 365 mmol·g
−1
·h
−1
with 100% of selectivity for H
2
at 80 °C, which is 2.2 and 2.0 times that of commercial Pd/C and Pt/C, respectively. Further mechanistic studies demonstrate that HCOO* is the intermediate in HCOOH dehydrogenation over Ti
3
C
2
T
x
MXenes with different coverages of surface oxygen atoms. Increasing the oxygen coverage on the surface of Ti
3
C
2
T
x
MXenes not only promotes the conversion from HCOO* to CO
2
* by lowering the energy barrier, but also weakens the adsorption energy of CO
2
and H
2
, thus accelerating the dehydrogenation of HCOOH.
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