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Current techno-economic evaluation manifests that the electrochemical CO 2 reduction reaction (eCO 2 RR) to CO is very promising considering its simple two-electron transfer process, minimum cost of electricity, and low separation cost. Herein, we report a Sn-modification strategy that can tune the local electronic structure of Cu with an appropriate valence. The as-prepared catalysts can alter the broad product distribution of Cu-based eCO 2 RR to predominantly generate CO. CO faradaic efficiency (FE) remained above 96% in the wide potential range of -0.5 to -0.9 V vs. the reversible hydrogen electrode (RHE) with CO partial current density up to 265 mA cm -2 . The catalyst also had remarkable stability. Operando experiments and density functional theory calculations demonstrated that the surface Cu δ + sites could be modulated and stabilized after introducing Sn. The Cu δ + sites with low positive valence were conducive to regulating the binding energy of intermediates and resulted in high CO selectivity and maintained the stability of the catalyst. Additionally, scaling up the catalyst into a membrane electrode assemble system (MEA) could achieve a high overall current of 1.3 A with exclusive and stable CO generation., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)

Developing electrocatalytic reactions with high-efficiency can make important contributions to carbon neutrality. However, poor long-term stability of catalysts is a bottleneck for its practical application. Herein, an "in situ periodic regeneration of catalyst (PR-C)" strategy is proposed to give long-term high efficiency of CO 2 electroreduction to generate C 2+ products over Cu catalyst by applying a positive potential pulse for a short time periodically in the halide-containing electrolyte. The high Faradaic efficiency (81.2 %) and current density (22.6 mA cm -2 ) could be maintained completely at least 36 h, while the activity and selectivity decreased continuously without using the PR-C method. Control experiments and operando characterization demonstrated that the surface structure and oxidation state of Cu could be recovered periodically by the PR-C method, which was beneficial for CO 2 activation and C-C coupling., (© 2022 Wiley-VCH GmbH.)

The properties of supports have a significant effect on the activity of noble metal single atoms. In this work, Co-doped CeO 2 -supported single-atom Pt catalysts (Pt 1 /Co-CeO 2 ) have been acquired by a synchronous pyrolysis/deposition route and demonstrated to promote low-temperature oxidation of CO. Revealed by a model reaction of 1% CO + 1% O 2 + 98% He at a space velocity of 12,000 mL/g cat /h, CO conversion (100 °C) acquired on a (0.5% Pt)/(10% Co-CeO 2 ) catalyst (36.6%) was 3.6 and 4.9 times those of 0.5% Pt/CeO 2 (10.0%) and 10% Co-CeO 2 (7.4%) catalysts and 2.1 times that of their conversion sum (17.4%), confirming the positive role of the Co dopant in boosting the low-temperature oxidation of CO. The consistent results are also verified in the comparison of Pt 1 /Co-ZnO with Pt 1 /ZnO and Pt 1 /Co-Al 2 O 3 with Pt 1 /Al 2 O 3 . In addition, the activity of single-atom Pt 1 /Co-CeO 2 catalysts can be facilely modified by changing the loading of Pt and/or doping amount of Co. These reasonable data will provide a methodology to access more applicable catalysts for CO oxidation at low temperature.

The electroreduction of CO 2 to CH 4 has attracted extensive attention. However, it is still a challenge to achieve high current density and faradaic efficiency (FE) for producing CH 4 because the reaction involves eight electrons and four protons. In this work, we designed Cu nanoparticles supported on N-doped carbon (Cu-np/NC). It was found that the catalyst exhibited outstanding performance for the electroreduction of CO 2 to CH 4 . The FE toward CH 4 could be as high as 73.4% with a high current density of 320 mA cm -2 . In addition, the mass activity could reach up to 6.4 A mg Cu -1 . Both experimental and theoretical calculations illustrated that the pyrrolic N in NC could accelerate the hydrogenation of *CO to the *CHO intermediate, resulting in high current density and excellent selectivity for CH 4 . This work conducted the first exploration of the effect of N-doped species in composites on the electrocatalytic performance of CO 2 reduction., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A coupling catalyst of highly dispersed N, P co-doped carbon frames (NPCFs) anchored with Fe single atoms (SAs) and Fe 2 P nanoparticles (NPs) is synthesized by a novel in situ doping-adsorption-phosphatization strategy for the electrocatalytic oxygen reduction reaction (ORR). The optimized Fe SAs-Fe 2 P NPs/NPCFs-2.5 catalyst shows a superior ORR activity and stability in 0.5 m H 2 SO 4 and 0.1 m KOH, respectively. Theoretical calculations reveal a synergistic effect, in that the existence of Fe 2 P weakens the adsorption of ORR intermediates on active sites and lowers the reaction free energy. The doped P atoms with a strong electron-donating ability elevate the energy level of Fe-3d orbitals and facilitate the adsorption of O 2 . The active Fe atoms exist in a low oxidation state and are less positively charged, and they serve as an electron reservoir capable of donating and releasing electrons, thus improving the ORR activity. Operando and in situ characterization results indicate that the atomically dispersed FeN 4 /FeP coupled active centers in the Fe SAs-Fe 2 P NPs/NPCFs-2.5 catalyst are characteristic of the different catalytic mechanisms in acidic and alkaline media. This work proposes a novel idea for constructing coupling catalysts with atomic-level precision and provides a strong reference for the development of high-efficiency ORR electrocatalysts for practical application., (© 2022 Wiley-VCH GmbH.)

A encapsulation-adsorption-pyrolysis strategy for the construction of atomically dispersed Co-Te diatomic sites (DASs) that are anchored in N-doped carbon is reported as an efficient bifunctional catalyst for electrocatalytic hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The as-constructed catalyst shows the stable CoN 3 C 1 -TeN 1 C 3 coordination structure before and after HER and ORR. The *OOH/*H intermediate species are captured by in situ Raman and in situ attenuated total reflectance-surface enhanced infrared absorption spectroscopy, indicating that the reactant O 2 /H 2 O molecule has a strong interaction with the Co site, revealing that Co δ+ is an effective active site. Theoretical calculations show that the Co δ+ has adsorption-activation function and the neighboring Te δ+ acts as an electron donor adjusting the electronic structure of Co δ+ , promoting the dissociation of H 2 O molecules and the adsorption of H and oxygen-containing intermediates in HER and ORR. In the meanwhile, the nearest C atom around Co also profoundly affects the adsorption of H atoms. This results in the weakening of the OH adsorption and enhancement of H adsorption, as well as the more stable water molecule dissociation transition state, thus significantly boosting ORR and HER performance., (© 2022 Wiley-VCH GmbH.)

Herein, a novel strategy has been proposed to design a hollow structure via post-modified N sites coordinating to metal species. As a result, an atomically dispersed Co site catalyst with high loading has been obtained and has shown superb performance in CO 2 cycloaddition to ethylene carbonate. This novel avenue can be extended to other atomically dispersed metal catalysts with high loading.

Electroreduction of CO 2 into valuable fuels and feedstocks offers a promising way for CO 2 utilization. However, the commercialization is limited by the low productivity. Here, we report a strategy to enhance the productivity of CO 2 electroreduction by improving diffusion of CO 2 to the surface of catalysts using porous organic cages (POCs) as an additive. It was noted that the Faradaic efficiency (FE) of C2+ products could reach 76.1 % with a current density of 1.7 A cm -2 when Cu-nanorod(nr)/CC3 (one of the POCs) was used, which were much higher than that using Cu-nr. Detailed studies demonstrated that the hydrophobic pores of CC3 can adsorb a large amount of CO 2 for the reaction, and the diffusion of CO 2 in the CC3 to the nanocatalyst surface is easier than that in the liquid electrolyte. Thus, more CO 2 molecules make contact with the nanocatalysts in the presence of CC3, enhancing CO 2 reduction and inhibiting generation of H 2 ., (© 2022 Wiley-VCH GmbH.)

Hydrogen production by water splitting and seawater electrolysis is a promising alternative to develop clean hydrogen energy. The construction of high-efficiency and durable electrocatalysts for the hydrogen evolution reaction (HER) in a wide pH range and seawater is critical to overcoming the sluggish kinetic process. Herein, we develop an efficient catalytic material composed of a single-atom Ru-N 4 site and Ru nanoparticles anchored on nitrogen-doped carbon (Ru 1+NPs /N-C) through the coordination-pyrolysis strategy of the melamine formaldehyde resin. The Ru 1+NPs /N-C catalyst shows outstanding HER activity with the smallest overpotentials, the lowest Tafel slopes, the highest mass activity and turnover frequency, as well as excellent stability in both acidic and alkaline media. Moreover, Ru 1+NPs /N-C shows comparable hydrogen production performance and a higher faradic efficiency to 20% Pt/C in natural seawater and artificial simulated seawater. Theoretical calculations demonstrate that the strong synergistic effects between the Ru-N 4 site and Ru nanoparticles modify the electronic structure to accelerate the HER kinetics. Ru nanoparticles can effectively realize dissociation of H 2 O to generate adsorbed hydrogen and also promote the single-atom Ru-N 4 site to combine adsorbed hydrogen to H 2 and desorption. This work provides a new perspective for designing high-efficiency hydrogen production electrocatalysts for large-scale seawater electrolysis.

High-performance, fully atomically dispersed single-atom catalysts (SACs) are promising candidates for next-generation industrial catalysts. However, it remains a great challenge to avoid the aggregation of isolated atoms into nanoparticles during the preparation and application of SACs. Here, the evolution of Pd species is investigated on different crystal facets of CeO 2 , and vastly different behaviors on the single-atomic dispersion of surface Pd atoms are surprisingly discovered. In situ X-ray photoelectron spectroscopy (XPS), in situ near-ambient-pressure-XPS (NAP-XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray absorption spectroscopy (XAS) reveal that, in a reducing atmosphere, more oxygen vacancies are generated on the (100) facet of CeO 2 , and Pd atoms can be trapped and thus feature atomic dispersion; by contrast, on the CeO 2 (111) facet, Pd atoms will readily aggregate into clusters (Pd n ). Furthermore, Pd 1 /CeO 2 (100) gives a high selectivity of 90.3% for the catalytic N-alkylation reaction, which is 2.8 times higher than that for Pd n /CeO 2 (111). This direct evidence demonstrates the crucial role of crystal-facet effects in the preparation of metal-atom-on-metal-oxide SACs. This work thus opens an avenue for the rational design and targeted synthesis of ultrastable and sinter-resistant SACs., (© 2022 Wiley-VCH GmbH.)

Recognizing and controlling the structure-activity relationships of single-atom catalysts (SACs) is vital for manipulating their catalytic properties for various practical applications. Herein, Fe SACs supported on nitrogen-doped carbon (SA-Fe/CN) are reported, which show high catalytic reactivity (97% degradation of bisphenol A in only 5 min), high stability (80% of reactivity maintained after five runs), and wide pH suitability (working pH range 3-11) toward Fenton-like reactions. The roles of different N species in these reactions are further explored, both experimentally and theoretically. It is discovered that graphitic N is an adsorptive site for the target molecule, pyrrolic N coordinates with Fe(III) and plays a dominant role in the reaction, and pyridinic N, coordinated with Fe(II), is only a minor contributor to the reactivity of SA-Fe/CN. Density functional theory (DFT) calculations reveal that a lower d-band center location of pyrrolic-type Fe sites leads to the easy generation of Fe-oxo intermediates, and thus, excellent catalytic properties., (© 2022 Wiley-VCH GmbH.)

Activation of O 2 is a crucial step in oxidation processes. Here, the concept of sp-hybridized C≡C triple bonds as an electron donor is adopted to develop highly active and stable catalysts for molecular oxygen activation. We demonstrate that the neighboring sp-hybridized C and Cu sites on the interface of the sub-nanocluster CuO/graphdiyne are the key structures to effectively modulate the O 2 activation process in the bridging adsorption mode. The as-prepared sub-nanocluster CuO/graphdiyne catalyst exhibited the highest CO oxidation activity and readily converted 50% CO at around 133 °C, which is 34 and 94 °C lower than that for CuO/graphene and CuO/active carbon catalysts, respectively. In situ diffused reflectance infrared Fourier transform spectroscopy and density functional theory calculation results proved that the neighboring sp-hybridized C is more favorable to promote the rapid dissociation of carbonate than sp 2 -hybridized C without overcoming any energy barrier. The gaseous CO directly reacts with the active molecular oxygen and tends to proceed through the E-R mechanism with a relatively low energy barrier (0.20 eV). This work revealed that sp-hybridized C of graphdiyne-based materials could effectively improve the O 2 activation efficiency, which could facilitate the low-temperature oxidation processes.

Photocatalytic CO 2 conversion into a high-value-added C 2 product is a highly challenging task because of insufficient electron deliverability and sluggish C-C coupling kinetics. Engineering catalytic interfaces in photocatalysts provides a promising approach to manipulate photoinduced charge carriers and create multiple catalytic sites for boosting the generation of C 2 product from CO 2 reduction. Herein, a Cu δ+ /CeO 2 -TiO 2 photocatalyst that contains atomically dispersed Cu δ+ sites anchored on the CeO 2 -TiO 2 heterostructures consisting of highly dispersed CeO 2 nanoparticles on porous TiO 2 is designedly constructed by the pyrolytic transformation of a Cu 2+ -Ce 3+ /MIL-125-NH 2 precursor. In the designed photocatalyst, TiO 2 acts as a light-harvesting material for generating electron-hole pairs that are efficiently separated by CeO 2 -TiO 2 interfaces, and the Cu-Ce dual active sites synergistically facilitate the generation and dimerization of *CO intermediates, thus lowering the energy barrier of C-C coupling. As a consequence, the Cu δ+ /CeO 2 -TiO 2 photocatalyst exhibits a production rate of 4.51 μmol -1 ·g cat -1 ·h -1 and 73.9% selectivity in terms of electron utilization for CO 2 to C 2 H 4 conversion under simulated sunlight, with H 2 O as hydrogen source and hole scavenger. The photocatalytic mechanism is revealed by operando spectroscopic methods as well as theoretical calculations. This study displays the rational construction of heterogeneous photocatalysts for boosting CO 2 conversion and emphasizes the synergistic effect of multiple active sites in enhancing the selectivity of C 2 product.

Electrocatalytic reduction of CO 2 (CO 2 RR) to value-added chemicals is of great significance for CO 2 utilization, however the CO 2 RR process involving multi-electron and proton transfer is greatly limited by poor selectivity and low yield. Herein, We have developed an atomically dispersed monovalent zinc catalyst anchored on nitrogenated carbon nanosheets (Zn/NC NSs). Benefiting from the unique coordination environment and atomic dispersion, the Zn/NC NSs exhibit a superior CO 2 RR performance, featuring a high current density up to 50 mA cm -2 with an outstanding CO Faradaic efficiency of ≈95 %. The center Zn I atom coordinated with three N atoms and one N atom that bridges over two adjacent graphitic edges (Zn-N 3+1 ) is identified as the catalytically active site. Experimental results reveal that the twisted Zn-N 3+1 structure accelerates CO 2 activation and protonation in the rate-determining step of *CO 2 to *COOH, while theoretical calculations elucidate that atomically dispersed Zn-N 3+1 moieties decrease the potential barriers for intermediate COOH* formation, promoting the proton-coupled CO 2 RR kinetics and boosting the overall catalytic performance., (© 2021 Wiley-VCH GmbH.)

Reducing CO 2 into fuels via photochemical reactions relies on highly efficient photocatalytic systems. Herein, we report a new and efficient photocatalytic system for CO 2 reduction. Driven by electrostatic attraction, an anionic metal-organic framework Cu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) as host and a cationic photosensitizer [Ru(phen) 3 ] 2+ (phen = 1,10-phenanthroline) as guest were self-assembled into a photocatalytic system Ru@Cu-HHTP , which showed high activity for photocatalytic CO 2 reduction under laboratory light source (CO production rate of 130(5) mmol g -1 h -1 , selectivity of 92.9%) or natural sunlight (CO production rate of 69.5 mmol g -1 h -1 , selectivity of 91.3%), representing the remarkable photocatalytic CO 2 reduction performance. More importantly, the photosensitizer [Ru(phen) 3 ] 2+ in Ru@Cu-HHTP is only about 1/500 in quantity reported in the literature. Theoretical calculations and control experiments suggested that the assembly of the catalysts and photosensitizers via electrostatic attraction interactions can provide a better charge transfer efficiency, resulting in high performance for photocatalytic CO 2 reduction.

Using renewable electricity to drive CO 2 electroreduction is an attractive way to achieve carbon-neutral energy cycle and produce value-added chemicals and fuels. As an important platform molecule and clean fuel, methanol requires 6-electron transfer in the process of CO 2 reduction. Currently, CO 2 electroreduction to methanol suffers from poor efficiency and low selectivity. Herein, we report the first work to design atomically dispersed Sn site anchored on defective CuO catalysts for CO 2 electroreduction to methanol. It exhibits high methanol Faradaic efficiency (FE) of 88.6 % with a current density of 67.0 mA cm -2 and remarkable stability in a H-cell, which is the highest FE(methanol) with such high current density compared with the results reported to date. The atomic Sn site, adjacent oxygen vacancy and CuO support cooperate very well, leading to higher double-layer capacitance, larger CO 2 adsorption capacity and lower interfacial charge transfer resistance. Operando experiments and density functional theory calculations demonstrate that the catalyst is beneficial for CO 2 activation via decreasing the energy barrier of *COOH dissociation to form *CO. The obtained key intermediate *CO is then bound to the Cu species for further reduction, leading to high selectivity toward methanol., (© 2021 Wiley-VCH GmbH.)

Guided by first-principles calculations, it was found that Cd single-atom catalysts (SACs) have excellent performance in activating CO 2 , and the introduction of axial coordination structure to Cd SACs cannot only further decrease the free energy barrier of CO 2 reduction, but also suppress the hydrogen evolution reaction (HER). Based on the above discovery, we designed and synthesized a novel Cd SAC that comprises an optimized CdN 4 S 1 moiety incorporated in a carbon matrix. It was shown that the catalyst exhibited outstanding performance in CO 2 electroreduction to CO. The faradaic efficiency (FE) of CO could reach up to 99.7 % with a current density of 182.2 mA cm -2 in a H-type electrolysis cell, and the turnover frequency (TOF) value could achieve 73000 h -1 , which was much higher than that reported to date. This work shows a successful example of how to design highly efficient catalysts guided by theoretical calculations., (© 2021 Wiley-VCH GmbH.)

Powered by a renewable electricity source, electrochemical CO 2 reduction reaction is a promising solution to facilitate the carbon balance. However, it is still a challenge to achieve a desired product with commercial current density and high efficiency. Herein we designed quasi-square-shaped cadmium hydroxide nanocatalysts for CO 2 electroreduction to CO. It was discovered that the catalyst is very active and selective for the reaction. The current density could be as high as 200 mA cm -2 with a nearly 100% selectivity in a commonly used H-type cell using the ionic liquid-based electrolyte. In addition, the faradaic efficiency of CO could reach 90% at a very low overpotential of 100 mV. Density functional theory studies and control experiments reveal that the outstanding performance of the catalyst was attributed to its unique structure. It not only provides low Cd-O coordination, but also exposes high activity (002) facet, which requires lower energy for the formation of CO. Besides, the high concentration of CO can be achieved from the low concentration CO 2 via an adsorption-electrolysis device., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Effecting the synergistic function of single metal atom sites and their supports is of great importance to achieve high-performance catalysts. Herein, we successfully fabricate polyoxometalates (POMs)-stabilized atomically dispersed platinum sites by employing three-dimensional metal-organic frameworks (MOFs) as the finite spatial skeleton to govern the accessible quantity, spatial dispersion, and mobility of metal precursors around each POM unit. The isolated single platinum atoms (Pt 1 ) are steadily anchored in the square-planar sites on the surface of monodispersed Keggin-type phosphomolybdic acid (PMo) in the cavities of various MOFs, including MIL-101, HKUST-1, and ZIF-67. In contrast, either the absence of POMs or MOFs yielded only platinum nanoparticles. Pt 1 -PMo@MIL-101 are seven times more active than the corresponding nanoparticles in the diboration of phenylacetylene, which can be attributed to the synergistic effect of the preconcentration of organic reaction substrates by porous MOFs skeleton and the decreased desorption energy of products on isolated Pt atom sites., (© 2021. The Author(s).)

Electrochemical reduction of CO 2 to chemicals and fuels is an interesting and attractive way to mitigate greenhouse gas emissions and energy shortages. In this work, we report the use of atomic In catalysts for CO 2 electroreduction to CO. The atomic In catalysts were anchored on N-doped carbon (In A /NC) through pyrolysis of In-based metal-organic frameworks (MOFs) and dicyandiamide. It was discovered that In A /NC had outstanding performance for selective CO production in the mixed electrolyte of ionic liquid/MeCN. It is different from those common In-based materials, in which formate/formic acid is formed as the main product. The faradaic efficiency (FE) of CO and total current density were 97.2% and 39.4 mA cm -2 , respectively, with a turnover frequency (TOF) of ∼40 000 h -1 . It is one of the highest TOF for CO production to date for all of the catalysts reported. In addition, the catalyst had remarkable stability. Detailed study indicated that In A /NC had higher double-layer capacitance, larger CO 2 adsorption capacity, and lower interfacial charge transfer resistance, leading to high activity for CO 2 reduction. Control experiments and theoretical calculations showed that the In-N site of In A /NC is not only beneficial for dissociation of COOH* to form CO but also hinders formate formation, leading to high selectivity toward CO instead of formate.

Electrocatalytic reduction of CO 2 into multicarbon (C 2+ ) products powered by renewable electricity offers one promising method for CO 2 utilization and promotes the storage of renewable energy under an ambient environment. However, there is still a dilemma in the manufacture of valuable C 2+ products between balancing selectivity and activity. In this work, cerium oxides were combined with CuO (CeO 2 /CuO) and showed an outstanding catalytic performance for C 2+ products. The faradaic efficiency of the C 2+ products could reach 75.2% with a current density of 1.21 A cm -2 . In situ experiments and density functional theory (DFT) calculations demonstrated that the interface between CeO 2 and Cu and the subsurface Cu 2 O coexisted in CeO 2 /CuO during CO 2 RR and two competing pathways for C-C coupling were promoted separately, of which hydrogenation of *CO to *CHO is energetically favoured. In addition, the introduction of CeO 2 also enhanced water activation, which could accelerate the formation rate of *CHO. Thus, the selectivity and activity for C 2+ products over CeO 2 /CuO can be improved simultaneously., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Oxide-derived copper (OD-Cu) has been discovered to be an effective catalyst for the electroreduction of CO 2 to C2+ products. The structure of OD-Cu and its surface species during the reaction process are interesting topics, which have not yet been clearly discussed. Herein, in situ surface-enhanced Raman spectroscopy (SERS), operando X-ray absorption spectroscopy (XAS), and 18 O isotope labeling experiments were employed to investigate the surface species and structures of OD-Cu catalysts during CO 2 electroreduction. It was found that the OD-Cu catalysts were reduced to metallic Cu(0) in the reaction. CuO x species existed on the catalyst surfaces during the CO 2 RR, which resulted from the adsorption of preliminary intermediates (such as *CO 2 and *OCO - ) on Cu instead of on the active sites of the catalyst. It was also found that abundant interfaces can be produced on OD-Cu, which can provide heterogeneous CO adsorption sites (strong binding sites and weak binding sites), leading to outstanding performance for obtaining C2+ products. The Faradaic efficiency (FE) for C2+ products reached as high as 83.8% with a current density of 341.5 mA cm -2 at -0.9 V vs. RHE., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

To relieve the green gas emission and involve the carbon neutral cycle, electrochemical reduction of CO 2 attracts more and more attention. Herein, a biatomic site catalyst of Cu-Fe coordinated with the nitrogen, which is doped in the carbon matrix (denoted as Cu-Fe-N 6 -C), is designed. The as-obtained Cu-Fe-N 6 -C exhibits higher performance than that of Cu-N-C and Fe-N-C, owing to bimetallic sites, proving synergistic functions based on different molecules and their interfaces. Cu-Fe-N 6 -C shows high selectivity toward CO, with high Faradaic efficiency (98% at -0.7 V), and maintaining 98% of its initial selectivity after 10 h electrolysis. The experimental results and theoretical calculations reveal that the synergistic catalysis of different metallic sites enlarges the adsorption enthalpy of CO 2 , reducing the activation energy result in generating high selectivity, activity, stability, and low impedance., (© 2020 Wiley-VCH GmbH.)

Developing efficient photocatalysts for synchronously producing H 2 and high value-added chemicals holds great promise to enhance solar energy conversion. Herein, a facile strategy of simultaneously engineering Pd cocatalyst and oxygen vacancies (V O s) on TiO 2 to promote H 2 production coupled with selective oxidation of benzylamine is demonstrated. The optimized Pd SA+C /TiO 2 -V O photocatalyst containing Pd single atoms (SAs), clusters (C), and V O s exhibits much superior performance to those of TiO 2 -V O and Pd SA /TiO 2 -V O counterparts. The production rates of H 2 and N-benzylidenebenzylamine over Pd SA+C /TiO 2 -V O are 52.7 and 1.5 times those over TiO 2 -V O , respectively. Both experimental and theoretical studies have elucidated the synergistic effect of Pd SAs, clusters, and V O s on TiO 2 in boosting the photocatalytic reaction. The presence of Pd SAs facilitates the generation and stabilization of abundant V O s by the formation of PdOTi 3+ atomic interface, while Pd clusters promote the photogenerated charge separation and afford the optimum active sites for H 2 evolution. Surface V O s of TiO 2 guarantee the efficient adsorption and dissociation/activation of reactant molecules. This study reveals the effect of active-site engineering on the photocatalysis and is expected to shed substantial light on future structure design and modulation of semiconductor photocatalysts., (© 2020 Wiley-VCH GmbH.)

Electroreduction of CO 2 to liquid fuels such as ethanol and n-propanol, powered by renewable electricity, offers a promising strategy for controlling the global carbon balance and addressing the need for the storage of intermittent renewable energy. In this work, we discovered that the composite composed of nitrogen-doped graphene quantum dots (NGQ) on CuO-derived Cu nanorods (NGQ/Cu-nr) was an outstanding electrocatalyst for the reduction of CO 2 to ethanol and n-propanol. The Faradaic efficiency (FE) of C2+ alcohols could reach 52.4 % with a total current density of 282.1 mA cm -2 . This is the highest FE for C2+ alcohols with a commercial current density to date. Control experiments and DFT studies show that the NGQ/Cu-nr could provide dual catalytic active sites and could stabilize the CH 2 CHO intermediate to enhance the FE of alcohols significantly through further carbon protonation. The NGQ and Cu-nr had excellent synergistic effects for accelerating the reduction of CO 2 to alcohols., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the area of catalysis, selective reduction of nitro compounds to amino compounds is a colossal challenge due to the existence of competitive reducible functional groups. Herein, an Fe-based catalyst Fe SAs /Fe 2 O 3ACs /N-doped polyhedral carbon (NPC) has been designed and synthesized. As we expected, compared with Fe SAs and Fe NPs , Fe SAs /Fe 2 O 3ACs /NPC shows excellent catalytic performance (turnover frequency up to 1923 h -1 , calculated with nitrobenzene), chemoselectivity, and tolerance during the hydrogenation reaction of nitro compounds under room temperature because of the synergistic effects between Fe SAs and Fe 2 O 3ACs . The theoretical calculations show that Fe SAs prefers to undergo hydrazine decomposition to generate hydrogen and the Fe 2 O 3ACs surface is more active toward the nitrobenzene reduction to aniline.

The development of low-cost, highly efficient and durable non-precious-metal (NPM) electrocatalysts for the oxygen reduction reaction (ORR) is of great significance. Herein, we report an ingenious two-step strategy for the fabrication of NPM electrocatalysts containing multifarious cobalt species embedded in nitrogen-rich nanocarbons (Co-N-C). Firstly, Co ions were fixed by coordination with 1H-Imidazo[4,5-f][1,10]phenanthroline (Hip), and secondly the Co-Hip precursor with abundant Co, C and N sources was subjected to calcination at various temperatures (700-900 °C). The obtained Co-N-C catalysts exhibited excellent activity in terms of the ORR in alkaline conditions, with a half-wave potential of 0.82 eV versus the reversible hydrogen electrode, which is close to that of commercial Pt/C. Moreover, the Co-N-C exhibited an unexpected catalytic activity with long-term stability and immunity to methanol which is better than commercial Pt/C catalyst, suggesting that Co-N-C with dual active sites of the single-atom Co sites (Co-N 4 ) and Co 2 N can be a promising alternative to replace Pt-based electrocatalysts in fuel cells. This work can provide a new route to designing promising catalysts with dual active sites for ORR.

Stabilized Cu + species have been widely considered as catalytic active sites in composite copper catalysts for catalytic reactions with industrial importance. However, few examples comprehensively explicated the origin of stabilized Cu + in a low-cost and widely investigated CuO/TiO 2 system. In this study, mass producible CuO/TiO 2 catalysts with interface-stabilized Cu + were prepared, which showed excellent low-temperature CO oxidation activity. A thorough characterization and theoretical calculations proved that the strong charge-transfer effect and Ti-O-Cu hybridization in Ti-doped CuO(111) at the CuO/TiO 2 interface contributed to the formation and stabilization of Cu + species. The CO molecule adsorbed on Cu + and reacted directly with Ti doping-promoted active lattice oxygen via a Mars-van Krevelen mechanism, leading to the enhanced low-temperature activity.

Atomically dispersed metal-N-C structures are efficient active sites for catalyzing benzene oxidation reaction (BOR). However, the roles of N and C atoms are still unclear. We report a polymerization-regulated pyrolysis strategy for synthesizing single-atom Fe-based catalysts, and present a systematic study on the coordination effect of Fe-N x C y catalytic sites in BOR. The special coordination environment of single-atom Fe sites brings a surprising discovery: Fe atoms anchored by four-coordinating N atoms exhibit the highest BOR performance with benzene conversion of 78.4% and phenol selectivity of 100%. Upon replacing coordinated N atoms by one or two C atoms, the BOR activities decrease gradually. Theoretical calculations demonstrate the coordination pattern influences not only the structure and electronic features, but also the catalytic reaction pathway and the formation of key oxidative species. The increase of Fe-N coordination number facilitates the generation and activation of the crucial intermediate O=Fe=O species, thereby enhancing the BOR activity.

Herein, a series of Fe-based catalysts have been designed and prepared by grinding a mixture of MIL-88d and melamine, and then the mixture was followed by pyrolysis. An unusual Fe/Fe 3 C-activated site is uniformly encapsulated in the N-doped carbon tubes obtained by pyrolysis of the film-like nanocrystals of MIL-88d. Experimental characterizations and theoretical calculations demonstrate that the surface N sites can effectively trap the nitrobenzene and aniline by their phenyl groups with the formation of three C-N bonds that made the catalyst exhibit excellent catalytic activity (turnover frequencies of ≤11268 h -1 calculated on the basis of nitrobenzene) and chemoselectivity for the reduction of nitro derivatives under facile conditions.

A central topic in single-atom catalysis is building strong interactions between single atoms and the support for stabilization. Herein we report the preparation of stabilized single-atom catalysts via a simultaneous self-reduction stabilization process at room temperature using ultrathin two-dimensional Ti 3- x C 2 T y MXene nanosheets characterized by abundant Ti-deficit vacancy defects and a high reducing capability. The single atoms therein form strong metal-carbon bonds with the Ti 3- x C 2 T y support and are therefore stabilized onto the sites previously occupied by Ti. Pt-based single-atom catalyst (SAC) Pt 1 /Ti 3- x C 2 T y offers a green route to utilizing greenhouse gas CO 2 , via the formylation of amines, as a C 1 source in organic synthesis. DFT calculations reveal that, compared to Pt nanoparticles, the single Pt atoms on Ti 3- x C 2 T y support feature partial positive charges and atomic dispersion, which helps to significantly decrease the adsorption energy and activation energy of silane, CO 2 , and aniline, thereby boosting catalytic performance. We believe that these results would open up new opportunities for the fabrication of SACs and the applications of MXenes in organic synthesis.

Metal-organic frameworks (MOF) have recently emerged as versatile precursors to fabricate functional MOF derivatives for oxygen evolution reactions (OER). Herein, we developed a controlled partial pyrolysis strategy to construct robust NiCo/Fe 3 O 4 heteroparticles within MOF-74 for efficient OER using trimetallic NiCoFe-MOF-74 as precursor. The partial pyrolysis method preserves the framework structure of MOF for effective substrates diffusion while producing highly active nanoparticles. The as-prepared NiCo/Fe 3 O 4 /MOF-74 delivered remarkably stable OER current with an overpotential as low as 238 mV at 10.0 mA cm -2 and an Tafel slop of 29 mV/dec, outperforming those of pristine NiCoFe-MOF-74, totally decomposed MOF derivatives, and most reported non-noble metal based electrocatalysts. The key for the formation of NiCo/Fe 3 O 4 /MOF-74 nanostructures is that the metals can be decomposed from NiCoFe-MOF-74 in the order of Ni, Co, and Fe under controlled heat treatment. Density functional theory calculations reveals that the underlying NiCo promotes the OER activity of Fe 3 O 4 through exchange stabilization of active oxygen species.

Multi-shelled hollow structured materials featuring large void volumes and high specific surface areas are very promising for a variety of applications. However, controllable synthesis of multi-shelled hollow structured intermetallic compounds remains a formidable challenge due to the high annealing temperature commonly required for the formation of intermetallic phases. Here, a topological self-template strategy was developed to solve this problem. Using this strategy, we prepared well-defined multi-shelled intermetallic Ni 3 Ga hollow microspheres (Ni 3 Ga-MIHMs) as disclosed by the HAADF-STEM, HRTEM, and EDS characterizations, and the BET specific surface areas of them measured as much as 153.4 m 2 g -1 . XRD and EXAFS spectral characterizations revealed the atomically ordered intermetallic phase nature of the Ni 3 Ga-MIHMs. The selective hydrogenation of acetylene catalytic evaluation results further demonstrated excellent catalytic properties of the Ni 3 Ga-MIHMs, which results from the more energetically facile reaction pathway for acetylene hydrogenation and ethylene desorption over it as revealed by DFT calculations. Besides, this strategy is also extendable to synthesize other multi-shelled intermetallic Ni 3 Sn 4 hollow microspheres, and is expected to open up new opportunities for rational design and preparation of novel structured and highly efficient intermetallics.

We develop an N-coordination strategy to design a robust CO 2 reduction reaction (CO 2 RR) electrocatalyst with atomically dispersed Co-N 5 site anchored on polymer-derived hollow N-doped porous carbon spheres. Our catalyst exhibits high selectivity for CO 2 RR with CO Faradaic efficiency (FE CO ) above 90% over a wide potential range from -0.57 to -0.88 V (the FE CO exceeded 99% at -0.73 and -0.79 V). The CO current density and FE CO remained nearly unchanged after electrolyzing 10 h, revealing remarkable stability. Experiments and density functional theory calculations demonstrate single-atom Co-N 5 site is the dominating active center simultaneously for CO 2 activation, the rapid formation of key intermediate COOH* as well as the desorption of CO.

Understanding the kinetics during the metal-insulator transition process is crucial to sort out the underlying physical nature of electron-lattice interactions in correlated materials. Here, based on the temperature-dependent in situ x-ray absorption fine structure measurement and density-functional theory calculations, we have revealed that the monoclinic-to-tetragonal phase transition of VO2 near the critical temperature is characterized by a sharp decrease of the twisting angle δ of the nearest V-V coordination. The VO2 metallization occurs in the intermediate monoclinic like structure with a large twist of V-V pairs when the δ angle is smaller than 1.4°. The correlation between structural kinetics and electronic structure points out that the structural rearrangement is a key factor to narrow the insulating band gap.