Mixed-Dimensional Partial Dealloyed PtCuBi/C as High-Performance Electrocatalysts for Methanol Oxidation with Enhanced CO Tolerance.

Developing efficient electrocatalysts for methanol oxidation reaction (MOR) is crucial in advancing the commercialization of direct methanol fuel cells (DMFCs). Herein, carbon-supported 0D/2D PtCuBi/C (0D/2D PtCuBi/C) catalysts are fabricated through a solvothermal method, followed by a partial electrochemical dealloying process to form a novel mixed-dimensional electrochemically dealloyed PtCuBi/C (0D/2D D-PtCuBi/C) catalysts. Benefiting from distinctive mixed-dimensional structure and composition, the as-obtained 0D/2D D-PtCuBi/C catalysts possess abundant accessible active sites. The introduction of Cu as a water-activating element weakens the COads, and oxophilic metal Bi facilitates the OHads, thereby enhancing its tolerance to CO poisoning and promoting MOR activity. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure spectroscopy (XAFS) collectively reveal the electron transfer from Cu and Bi to Pt, the electron-enrichment effect induced by dealloying, and the strong interactions among Pt-M (Cu, Pt, and Bi) multi-active sites, which improve the tuning of the electronic structure and enhancement of electron transfer ability. Impressively, the optimized 0D/2D D-PtCuBi/C catalysts exhibit the superior mass activity (MA) of 17.68 A mgPt -1 for MOR, which is 14.86 times higher than that of commercial Pt/C. This study offers a proposed strategy for Pt-based alloy catalysts, enabling their use as efficient anodic materials in fuel cell applications.

Ruthenium Single Atomic Sites Surrounding the Support Pit with Exceptional Photocatalytic Activity.

Single-metal atomic sites and vacancies can accelerate the transfer of photogenerated electrons and enhance photocatalytic performance in photocatalysis. In this study, a series of nickel hydroxide nanoboards (Ni(OH)x NBs) with different loadings of single-atomic Ru sites (w-SA-Ru/Ni(OH)x) were synthesized via a photoreduction strategy. In such catalysts, single-atomic Ru sites are anchored to the vacancies surrounding the pits. Notably, the SA-Ru/Ni(OH)x with 0.60 wt % Ru loading (0.60-SA-Ru/Ni(OH)x) exhibits the highest catalytic performance (27.6 mmol g-1 h-1) during the photocatalytic reduction of CO2 (CO2RR). Either superfluous (0.64 wt %, 18.9 mmol g-1 h-1; 3.35 wt %, 9.4 mmol-1 h-1) or scarce (0.06 wt %, 15.8 mmol g-1 h-1; 0.29 wt %, 21.95 mmol g-1 h-1; 0.58 wt %, 23.4 mmol g-1 h-1) of Ru sites have negative effect on its catalytic properties. Density functional theory (DFT) calculations combined with experimental results revealed that CO2 can be adsorbed in the pits; single-atomic Ru sites can help with the conversion of as-adsorbed CO2 and lower the energy of *COOH formation accelerating the reaction; the excessive single-atomic Ru sites occupy vacancies that retard the completion of CO2RR.

Improving CO2-to-C2+ Product Electroreduction Efficiency via Atomic Lanthanide Dopant-Induced Tensile-Strained CuOx Catalysts.

Cu is a promising electrocatalyst in CO2 reduction reaction (CO2RR) to high-value C2+ products. However, as important C-C coupling active sites, the Cu+ species is usually unstable under reduction conditions. How atomic dopants affect the performance of Cu-based catalysts is interesting to be studied. Herein, we first calculated the difference between the thermodynamic limiting potentials of CO2RR and the hydrogen evolution reaction, as well as the *CO binding energy over Cu2O doped with different metals, and the results indicated that doping atomic Gd into Cu2O could improve the performance of the catalyst effectively. On the basis of the theoretical study, we designed Gd1/CuOx catalysts. The distinctive electronic structure and large ion radii of Gd not only keep the Cu+ species stable during the reaction but also induce tensile strain in Gd1/CuOx, resulting in excellent performance of the catalysts for electroreduction of CO2 to C2+ products. The Faradic efficiency of C2+ products could reach 81.4% with a C2+ product partial current density of 444.3 mA cm-2 at -0.8 V vs a reversible hydrogen electrode. Detailed experimental and theoretical studies revealed that Gd doping enhanced CO2 activation on the catalyst, stabilized the key intermediate O*CCO, and reduced the energy barrier of the C-C coupling reaction.

Optimizing the Spatial Density of Single Co Sites via Molecular Spacing for Facilitating Sustainable Water Oxidation.

Advances in single-atom (-site) catalysts (SACs) provide a new solution of atomic economy and accuracy for designing efficient electrocatalysts. In addition to a precise local coordination environment, controllable spatial active structure and tolerance under harsh operating conditions remain great challenges in the development of SACs. Here, we show a series of molecule-spaced SACs (msSACs) using different acid anhydrides to regulate the spatial density of discrete metal phthalocyanines with single Co sites, which significantly improve the effective active-site numbers and mass transfer, enabling one of the msSACs connected by pyromellitic dianhydride to exhibit an outstanding mass activity of (1.63 ± 0.01) × 105 A·g-1 and TOFbulk of 27.66 ± 1.59 s-1 at 1.58 V (vs RHE) and long-term durability at an ultrahigh current density of 2.0 A·cm-2 under industrial conditions for oxygen evolution reaction. This study demonstrates that the accessible spatial density of single atom sites can be another important parameter to enhance the overall performance of catalysts.

Endowing Nanoparticles with High Stability on the Hydrogenation Reaction by the Amino Group-Assisted Strategy.

In the field of a heterogeneous industrial catalysis process, the encapsulated structure plays a crucial role in preventing active sites from leaching during the reaction; however, related studies on the strategy to fabricate encapsulated catalysts under control remain rare. Herein, we develop an amino-assisted strategy to construct a highly stable catalyst with core-shell copper nanoparticles (NPs), namely, Cu@NC (NC represents the nitrogen-doped carbon), presenting not only excellent activity but also high durability on the hydrogenation of quinolines even in the large-scale tests, which is very vital in practical application. In contrast, in the absence of the amino group, the Cu NPs were dispersed out of the carbon surface to form Cu/NC, leading to readily lose activity in the recycling tests due to the leaching occurred during the catalytic process. This work offers a promising method to fabricate a stable catalyst to enhance durability in heterogeneous catalysis.

p-Block Bismuth Nanoclusters Sites Activated by Atomically Dispersed Bismuth for Tandem Boosting Electrocatalytic Hydrogen Peroxide Production.

Constructing electrocatalysts with p-block elements is generally considered rather challenging owing to their closed d shells. Here for the first time, we present a p-block-element bismuth-based (Bi-based) catalyst with the co-existence of single-atomic Bi sites coordinated with oxygen (O) and sulfur (S) atoms and Bi nanoclusters (Biclu ) (collectively denoted as BiOSSA /Biclu ) for the highly selective oxygen reduction reaction (ORR) into hydrogen peroxide (H2 O2 ). As a result, BiOSSA /Biclu gives a high H2 O2 selectivity of 95 % in rotating ring-disk electrode, and a large current density of 36 mA cm-2 at 0.15 V vs. RHE, a considerable H2 O2 yield of 11.5 mg cm-2 h-1 with high H2 O2 Faraday efficiency of ∼90 % at 0.3 V vs. RHE and a long-term durability of ∼22 h in H-cell test. Interestingly, the experimental data on site poisoning and theoretical calculations both revealed that, for BiOSSA /Biclu , the catalytic active sites are on the Bi clusters, which are further activated by the atomically dispersed Bi coordinated with O and S atoms. This work demonstrates a new synergistic tandem strategy for advanced p-block-element Bi catalysts featuring atomic-level catalytic sites, and the great potential of rational material design for constructing highly active electrocatalysts based on p-block metals.

Directional and Ultrafast Charge Transfer in Oxygen-Vacancy-Rich ZnO@Single-Atom Cobalt Core-Shell Junction for Photo-Fenton-Like Reaction.

In photosynthesis, solar energy is harvested by photosensitizers, and then, the excited electrons transfer via a Z-Scheme mode to enzymatic catalytic centers to trigger redox reactions. Herein, we constructed a core-shell Z-scheme heterojunction of semiconductor@single-atom catalysts (SACs). The oxygen-vacancy-rich ZnO core and single-atom Co-N4 sites supported on nitrogen-rich carbon shell (SA-Co-CN) act as the photosensitizer and the enzyme-mimicking active centers, respectively. Driven by built-in electric field across the heterojunction, photoexcited electrons could rapidly (2 ps) transfer from the n-type ZnO core to the p-type SA-Co-CN shell, finally boosting the catalytic performance of the surface-exposed single-atom Co-N4 sites for peroxymonosulfate (PMS) activation under light irradiation. The synergies between photocatalysis and heterogeneous Fenton-like reaction lead to phenomenally enhanced production of various reactive oxygen species for rapid degradation of various microcontaminants in water. Experimental and theoretical results validate that the interfacial coupling of SA-Co-CN with ZnO greatly facilitates PMS adsorption and activation by reducing the adsorption energy and enhancing the cascade electron transfer processes for the photo-Fenton-like reaction.

Neighboring sp-Hybridized Carbon Participated Molecular Oxygen Activation on the Interface of Sub-nanocluster CuO/Graphdiyne.

Activation of O2 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 O2 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 sp2-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 O2 activation efficiency, which could facilitate the low-temperature oxidation processes.

Atomically Dispersed CoN3 C1 -TeN1 C3 Diatomic Sites Anchored in N-Doped Carbon as Efficient Bifunctional Catalyst for Synergistic Electrocatalytic Hydrogen Evolution and Oxygen Reduction.

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 CoN3 C1 -TeN1 C3 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 O2 /H2 O molecule has a strong interaction with the Co site, revealing that Coδ+ is an effective active site. Theoretical calculations show that the Coδ+ has adsorption-activation function and the neighboring Teδ+ acts as an electron donor adjusting the electronic structure of Coδ+ , promoting the dissociation of H2 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.

Boosting the Activity of Single-Atom Pt1/CeO2 via Co Doping for Low-Temperature Catalytic Oxidation of CO.

The properties of supports have a significant effect on the activity of noble metal single atoms. In this work, Co-doped CeO2-supported single-atom Pt catalysts (Pt1/Co-CeO2) 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% O2 + 98% He at a space velocity of 12,000 mL/gcat/h, CO conversion (100 °C) acquired on a (0.5% Pt)/(10% Co-CeO2) catalyst (36.6%) was 3.6 and 4.9 times those of 0.5% Pt/CeO2 (10.0%) and 10% Co-CeO2 (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 Pt1/Co-ZnO with Pt1/ZnO and Pt1/Co-Al2O3 with Pt1/Al2O3. In addition, the activity of single-atom Pt1/Co-CeO2 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.

High-Areal Density Single-Atoms/Metal Oxide Nanosheets: A Micro-Gas Blasting Synthesis and Superior Catalytic Properties.

The two-dimensional nanosheets are conducive to not only endow opened surfaces for loading active metal atoms but also boost the mass transfer for the heterogeneous reactions. The challenge is how to load and stabilize single-atoms on nanosheets in high-areal densities. This work reports an efficient micro-gas blasting (MGB) strategy to access versatile noble metal single-atoms/metal oxide nanosheets, including Ir1 /CoOx , Pd1 /CeO2 , etc. Especially for Pt/CeO2 nanosheets (Pt1 /CeO2 -S), the Pt loading is increased to 15 at%. The Pt1 /CeO2 -S catalysts from MGB are revealed to possess superior reactivity and tolerance in the model reaction of water-gas shift (WGS). The Pt1 /CeO2 -S catalyst exhibit 2-3 times reactivity that of their thicker counterpart, single-atom Pt1 /CeO2 microspheric catalyst. Moreover, the single-atom sites in Pt1 /CeO2 -S (1-10 %) catalysts are stable in a harsh WGS reaction condition of 10 % CO. This work thus paves a way to access the practical single-atom catalysts.

Boosting the Productivity of Electrochemical CO2 Reduction to Multi-Carbon Products by Enhancing CO2 Diffusion through a Porous Organic Cage.

Electroreduction of CO2 into valuable fuels and feedstocks offers a promising way for CO2 utilization. However, the commercialization is limited by the low productivity. Here, we report a strategy to enhance the productivity of CO2 electroreduction by improving diffusion of CO2 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 CO2 for the reaction, and the diffusion of CO2 in the CC3 to the nanocatalyst surface is easier than that in the liquid electrolyte. Thus, more CO2 molecules make contact with the nanocatalysts in the presence of CC3, enhancing CO2 reduction and inhibiting generation of H2 .

Promoting CO2 Electroreduction Kinetics on Atomically Dispersed Monovalent ZnI Sites by Rationally Engineering Proton-Feeding Centers.

Electrocatalytic reduction of CO2 (CO2 RR) to value-added chemicals is of great significance for CO2 utilization, however the CO2 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 CO2 RR performance, featuring a high current density up to 50 mA cm-2 with an outstanding CO Faradaic efficiency of ≈95 %. The center ZnI atom coordinated with three N atoms and one N atom that bridges over two adjacent graphitic edges (Zn-N3+1 ) is identified as the catalytically active site. Experimental results reveal that the twisted Zn-N3+1 structure accelerates CO2 activation and protonation in the rate-determining step of *CO2 to *COOH, while theoretical calculations elucidate that atomically dispersed Zn-N3+1 moieties decrease the potential barriers for intermediate COOH* formation, promoting the proton-coupled CO2 RR kinetics and boosting the overall catalytic performance.

In Situ Periodic Regeneration of Catalyst during CO2 Electroreduction to C2+ Products.

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 CO2 electroreduction to generate C2+ 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 CO2 activation and C-C coupling.

Electrostatic Attraction-Driven Assembly of a Metal-Organic Framework with a Photosensitizer Boosts Photocatalytic CO2 Reduction to CO.

Reducing CO2 into fuels via photochemical reactions relies on highly efficient photocatalytic systems. Herein, we report a new and efficient photocatalytic system for CO2 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 CO2 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 CO2 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 CO2 reduction.

Atomic Indium Catalysts for Switching CO2 Electroreduction Products from Formate to CO.

Electrochemical reduction of CO2 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 CO2 electroreduction to CO. The atomic In catalysts were anchored on N-doped carbon (InA/NC) through pyrolysis of In-based metal-organic frameworks (MOFs) and dicyandiamide. It was discovered that InA/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 InA/NC had higher double-layer capacitance, larger CO2 adsorption capacity, and lower interfacial charge transfer resistance, leading to high activity for CO2 reduction. Control experiments and theoretical calculations showed that the In-N site of InA/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.

Synergistic Pd Single Atoms, Clusters, and Oxygen Vacancies on TiO2 for Photocatalytic Hydrogen Evolution Coupled with Selective Organic Oxidation.

Developing efficient photocatalysts for synchronously producing H2 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 (VO s) on TiO2 to promote H2 production coupled with selective oxidation of benzylamine is demonstrated. The optimized PdSA+C /TiO2 -VO photocatalyst containing Pd single atoms (SAs), clusters (C), and VO s exhibits much superior performance to those of TiO2 -VO and PdSA /TiO2 -VO counterparts. The production rates of H2 and N-benzylidenebenzylamine over PdSA+C /TiO2 -VO are 52.7 and 1.5 times those over TiO2 -VO , respectively. Both experimental and theoretical studies have elucidated the synergistic effect of Pd SAs, clusters, and VO s on TiO2 in boosting the photocatalytic reaction. The presence of Pd SAs facilitates the generation and stabilization of abundant VO s by the formation of PdOTi3+ atomic interface, while Pd clusters promote the photogenerated charge separation and afford the optimum active sites for H2 evolution. Surface VO s of TiO2 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.

Design of Binary Cu-Fe Sites Coordinated with Nitrogen Dispersed in the Porous Carbon for Synergistic CO2 Electroreduction.

To relieve the green gas emission and involve the carbon neutral cycle, electrochemical reduction of CO2 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-N6 -C), is designed. The as-obtained Cu-Fe-N6 -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-N6 -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 CO2 , reducing the activation energy result in generating high selectivity, activity, stability, and low impedance.

Boosting CO2 Electroreduction over a Cadmium Single-Atom Catalyst by Tuning of the Axial Coordination Structure.

Guided by first-principles calculations, it was found that Cd single-atom catalysts (SACs) have excellent performance in activating CO2 , and the introduction of axial coordination structure to Cd SACs cannot only further decrease the free energy barrier of CO2 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 CdN4 S1 moiety incorporated in a carbon matrix. It was shown that the catalyst exhibited outstanding performance in CO2 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.

Highly Efficient CO2 Electroreduction to Methanol through Atomically Dispersed Sn Coupled with Defective CuO Catalysts.

Using renewable electricity to drive CO2 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 CO2 reduction. Currently, CO2 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 CO2 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 CO2 adsorption capacity and lower interfacial charge transfer resistance. Operando experiments and density functional theory calculations demonstrate that the catalyst is beneficial for CO2 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.