Syngas, a CO and H2 mixture mostly generated from non-renewable fossil fuels, is an essential feedstock for production of liquid fuels. Electrochemical reduction of CO2 and H+/H2O is an alternative renewable route to produce syngas. Here we introduce the concept of coupling a hydrogen evolution reaction (HER) catalyst with a CDots/C3N4 composite (a CO2 reduction catalyst) to achieve a cheap, stable, selective and efficient route for tunable syngas production. Co3O4, MoS2, Au and Pt serve as the HER component. The Co3O4-CDots-C3N4 electrocatalyst is found to be the most efficient among the combinations studied. The H2/CO ratio of the produced syngas is tunable from 0.07:1 to 4:1 by controlling the potential. This catalyst is highly stable for syngas generation (over 100 h) with no other products besides CO and H2. Insight into the mechanisms balancing between CO2 reduction and H2 evolution when applying the HER-CDots-C3N4 catalyst concept is provided.
Electrochemical
reduction of CO2 to carbon-containing
fuels possesses the potential to solve the environmental issues caused
by excess CO2 in the atmosphere. Herein, we introduce a
ternary Au-CDots-C3N4 electrocatalyst for efficiently
reducing CO2 to CO. The ternary catalyst exhibited significantly
enhanced activity and stability for CO2 electroreduction
in comparison with pure Au NPs. The Au-CDots-C3N4 electrocatalyst demonstrates a high CO FE of ∼79.8% at −0.5
V and a 2.8-fold enhancement of current density (with the Au loading
only 4 wt %) at −1.0 V relative to pure Au NPs. The DFT calculations
and experimental observations indicate that the high activity toward
CO2RR originates from the synergetic effect among Au NPs, CDots, and
C3N4 and the capability of H+ and
CO2 adsorption from CDots. The long-term stability tests
demonstrate that the electrocatalyst can be used for over 8 h without
obvious deactivations and maintained its activity over 60 days under
normal conditions.
Chiral
carbon dots (CDs) integrated the advantages of achiral CDs
and the unique chiral property, which expand the prospect of the biological
applications of CDs. However, the structure control and the origin
of chirality for chiral CDs remain unclear. Herein, chiral CDs were
obtained by thermal polymerization of chiral amino acids and citric
acid, and their handedness of chirality could be controlled by adjusting
the reaction temperature, which leads to different kinds of surface
modifications. With aliphatic amino acids as a chiral source, all
of the CDs that reacted at different temperatures (90–200 °C)
have the same handedness of the chiral source. But with aromatic amino
acids as a chiral source, CDs with maintained or inversed handedness
compared with the chiral source could be obtained by adjusting the
reaction temperature. Below a temperature of 120 °C, the chiral
source was modified with CDs by esterification and transferred the
handedness of chirality; at high temperatures (above 150 °C),
which mainly connected by amidation accompanying with the formation
of rigid structure generated by the π conjugation between the
aromatic nucleus of chiral source and the carbon core of CDs, caused
the inversing of the chiral signal. Further, we investigated the chiral
effects of CDs on the glucose oxidase activity for a highly sensitive
electrochemical biosensor.
Hydrogen production by photocatalytic overall water-splitting represents an ideal pathway for clean energy harvesting, for which developing high-efficiency catalysts has been the central scientific topic. Nanosized CoO with high solar-to-hydrogen efficiency (5%) is one of the most promising catalyst candidates. However, poor understanding of this photocatalyst leaves the key issue of rapid deactivation unclear and severely hinders its wide application. Here, we report a sub-micrometer CoO octahedron photocatalyst with high overall-water-splitting activity and outstanding ability of HO-resistance poisoning. We show that the deactivation of CoO catalyst originates from the unintended thermoinduced oxidation of CoO during photocatalysis, with coexistence of oxygen and water. We then demonstrate that introduction of graphene, as a heat conductor, largely enhanced the photocatalytic activity and stability of the CoO. Our work not only provides a new insight of CoO for photocatalytic water splitting but also demonstrates a new concept for photocatalyst design.
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