Unveiling the active phase of catalytic materials under reaction conditions is important for the construction of efficient electrocatalysts for selective nitrate reduction to ammonia. The origin of ...the prominent activity enhancement for CuO (Faradaic efficiency: 95.8 %, Selectivity: 81.2 %) toward selective nitrate electroreduction to ammonia was probed. 15N isotope labeling experiments showed that ammonia originated from nitrate reduction. 1H NMR spectroscopy and colorimetric methods were performed to quantify ammonia. In situ Raman and ex situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The combined results of online differential electrochemical mass spectrometry (DEMS) and DFT calculations demonstrated that the electron transfer from Cu2O to Cu at the interface could facilitate the formation of *NOH intermediate and suppress the hydrogen evolution reaction, leading to high selectivity and Faradaic efficiency.
Ammonia boost: CuO NWAs are efficient nitrate electroreduction catalysts for the selective synthesis of ammonia. In situ experiments revealed that CuO was electrochemically converted into Cu/Cu2O, which serves as an active phase. The electron transfer at the interface of Cu/Cu2O could facilitate the formation of *NOH intermediate and suppress the competitive H2 production.
NiMo alloys are efficient electrocatalysts in alkaline water electrolyzer for the hydrogen evolution reaction (HER). Metals are usually considered to be stable during the cathodic process. However, ...the actual behaviors of Mo in the NiMo alloys are unexplored. Here, we present the instability of Mo in the Ni4Mo alloy as a highly efficient HER electrocatalyst in an alkaline medium. Mo in Ni4Mo is oxidized and dissolved in the form of MoO42− first. The dissolved MoO42− will re‐adsorb on the electrode surface and polymerize. Theoretical calculations indicate that the adsorption of the dimer Mo2O72− can promote the HER activity of metal Ni. The addition of MoO42− to the electrolyte can not only repair the durability of Ni4Mo alloy, but also facilitate the HER activity of pure metal of Ni, Fe, and Co. Our findings provide insight into the structural transformation mechanism and performance‐enhanced origin of cathodic materials under the reaction conditions.
NiMo alloys, as one of the most efficient electrocatalysts in the alkaline electrolyzer, are unstable during the alkaline hydrogen evolution. An in situ transformation including oxidative dissolution of Mo in the form of MoO42−, the re‐adsorption of MoO42−, the polymerization of MoO42− to Mo2O72−, and the activity promotion by the Mo2O72− is presented.
Hydrogen (H2) is one of the most important clean and renewable energy sources for future energy sustainability. Nowadays, photocatalytic and electrocatalytic hydrogen evolution reactions (HERs) from ...water splitting are considered as two of the most efficient methods to convert sustainable energy to the clean energy carrier, H2. Catalysts based on transition metal dichalcogenides (TMDs) are recognized as greatly promising substitutes for noble‐metal‐based catalysts for HER. The photocatalytic and electrocatalytic activities of TMD nanosheets for the HER can be further improved after hybridization with many kinds of nanomaterials, such as metals, oxides, sulfides, and carbon materials, through different methods including the in situ reduction method, the hot‐injection method, the heating‐up method, the hydro(solvo)thermal method, chemical vapor deposition (CVD), and thermal annealing. Here, recent progress in photocatalytic and electrocatalytic HERs using 2D TMD‐based composites as catalysts is discussed.
Transition‐metal dichalcogenide (TMD)‐based catalysts have great promise as substitutes for noble‐metal‐based catalysts for hydrogen‐evolution reactions. Recent strategies regarding the various kinds of TMD‐based composites for photocatalytic and electrocatalytic hydrogen evolution are summarized here. In addition, the challenges and opportunities are provided.
Photocatalysis, which converts natural solar energy into chemical energy, has emerged as one of the most appealing technologies in the past decades. However, photocatalytic performances are limited ...by the poor absorption of visible light, charge‐carrier recombination during migration, and a high energy barrier for activating reactants. Oxygen vacancies in semiconductive metal oxides are reported to be vital to improve their photocatalytic efficiency. In this regard, this review provides a concise overview of oxygen vacancies in transition metal oxides in photocatalytic systems, including their functions, construction strategies, characterization methods, and applications. Moreover, an outlook on the current challenges and promising opportunities in this field is provided.
Oxygen vacancy engineering in semiconductive metal oxides is reported to be vital to improve photocatalytic efficiency. This review provides a concise overview of oxygen vacancies in transition metal oxides in photocatalytic systems, including their functions, construction strategies, characterization methods, and applications. Moreover, an outlook on the current challenges and promising opportunities in this research area is provided.
Nitrate is one of the essential raw ingredients in agriculture and industry. The electrochemical nitrogen oxidation reaction (NOR) is promising to replace the conventional nitrate synthesis industry ...with high energy consumption and greenhouse gas emission. Here, tensile‐strained palladium porous nanosheets (Pd‐s PNSs) were prepared. They exhibited enhanced activity for electrochemical NOR at ambient conditions, greatly outperforming Pd nanosheets. 15N isotope labeling experiments proved that nitrate originated from nitrogen oxidation. Combining electrochemical in situ Raman and FTIR spectroscopy with density functional calculations, it was revealed that the tensile strain could facilitate the formation of NOR active species of PdO2, leading to high activity.
Tensile‐strained palladium porous nanosheets exhibited enhanced activity for nitrogen electrooxidation to nitrate at ambient conditions. 15N isotope labeling experiments showed that nitrate originated from nitrogen electrooxidation. Electrochemical in situ characterizations and theoretical simulation revealed that the tensile strain could facilitate the formation of PdO2 active species and lead to high activity.
Commercial nitric acid (HNO
) and ammonia (NH
) are mostly produced through the Ostwald process and the Haber-Bosch process, respectively. However, high energy demand and enormous greenhouse gas ...accompy these processes. The development of economical and green ways to synthesize HNO
and NH
is highly desirable for solving the global energy and environmental crisis. Here, we present two energy-efficient and environmentally friendly strategies to synthesize HNO
and NH
at distributed sources, including the electrocatalytic oxidation of N
in air to HNO
and the electrocatalytic reduction of residual Formula: see text contamination in water to NH
. The isotope-labeling studies combined with theoretical calculation reveal the reaction path of the two proposed strategies, confirming the origin of the electrochemical products. Importantly, the electrooxidation-generated Formula: see text ions may also serve as reactants for the electroreduction synthesis of NH
in the future. Our work may open avenues for energy-efficient and green production of HNO
and NH
at distributed sources.
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•The principles of thermal promotion in photocatalysis were discussed.•The common thermal input patterns were summarized.•Thermally-assisted photocatalytic strategies in CO2 reduction ...were reviewed.•Challenges and prospects of thermally-assisted photocatalytic CO2 reduction were given.
Using heat or radiation as a single driving force for implementing carbon dioxide (CO2) conversion is usually limited by sluggish kinetics. Whereas the thermally-assisted photocatalysis by coupling utilization of solar energy and thermal energy has therefore provided a promising alternative strategy to boost the conversion of CO2 into high value-added synthetic fuels or chemicals under mild conditions. Herein, we will focus on the state-of-the-art advance in CO2 reduction to fuels by thermally-assisted photocatalysis, with emphases on the thermally-promoted principles, the thermal input patterns as well as the product distributions of CO2 reduction. In addition, some current challenges and perspectives will be discussed. This review not only gives a comprehensive and in-depth understanding of thermally-assisted photocatalytic CO2 reduction, but provides guidelines to other catalytic transformations (e.g. methane oxidation, nitrogen fixation, and organic coupling reactions) by integrating solar and thermal energy to enhance the reaction efficiency.
Abstract
Electrocatalytic alkyne semi-hydrogenation to alkenes with water as the hydrogen source using a low-cost noble-metal-free catalyst is highly desirable but challenging because of their ...over-hydrogenation to undesired alkanes. Here, we propose that an ideal catalyst should have the appropriate binding energy with active atomic hydrogen (H*) from water electrolysis and a weaker adsorption with an alkene, thus promoting alkyne semi-hydrogenation and avoiding over-hydrogenation. So, surface sulfur-doped and -adsorbed low-coordinated copper nanowire sponges are designedly synthesized via in situ electroreduction of copper sulfide and enable electrocatalytic alkyne semi-hydrogenation with over 99% selectivity using water as the hydrogen source, outperforming a copper counterpart without surface sulfur. Sulfur anion-hydrated cation (S
2−
-K
+
(H
2
O)
n
) networks between the surface adsorbed S
2−
and K
+
in the KOH electrolyte boost the production of active H* from water electrolysis. And the trace doping of sulfur weakens the alkene adsorption, avoiding over-hydrogenation. Our catalyst also shows wide substrate scopes, up to 99% alkenes selectivity, good reducible groups compatibility, and easily synthesized deuterated alkenes, highlighting the promising potential of this method.
For most metal-containing CO
reduction reaction (CO
RR) electrocatalysts, the unavoidable self-reduction to zero-valence metal will promote hydrogen evolution, hence lowering the CO
RR selectivity. ...Thus it is challenging to design a stable phase with resistance to electrochemical self-reduction as well as high CO
RR activity. Herein, we report a scenario to develop hydrocerussite as a stable and active electrocatalyst via in situ conversion of a complex precursor, tannin-lead(II) (TA-Pb) complex. A comprehensive characterization reveals the in situ transformation of TA-Pb to cerussite (PbCO
), and sequentially to hydrocerussite (Pb
(CO
)
(OH)
), which finally serves as a stable and active phase under CO
RR condition. Both experiments and theoretical calculations confirm the high activity and selectivity over hydrocerussite. This work not only offers a new approach of enhancing the selectivity in CO
RR by suppressing the self-reduction of electrode materials, but also provides a strategy for studying the reaction mechanism and active phases of electrocatalysts.
A facile surfactant‐assisted bottom‐up synthetic method to prepare a series of freestanding ultrathin 2D M‐TCPP (M = Zn, Cu, Cd or Co, TCPP = tetrakis(4‐carboxyphenyl)porphyrin) nanosheets with a ...thickness of sub‐10 nm is developed. As a proof‐of‐concept application, some of them are successfully used as new platforms for DNA detection. The Cu‐TCPP nanosheet‐based sensor shows excellent fluorescent sensing performance and is used for the simultaneous detection of multiple DNA targets.
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