Integrating bimetallic borides with g-C3N4 containing cyanamide defects for efficient photocatalytic nitrogen fixation.

The sustainable generation of ammonia by photocatalytic nitrogen fixation under mild conditions is fascinating compared to conventional industrial processes. Nevertheless, owing to the low charge transfer efficiency, the insufficient light absorption capacity and limited active sites of the photocatalyst cause the difficult adsorption and activation of N2 molecules, thereby resulting in a low photocatalytic conversion efficiency. Herein, a novel bimetallic CoMoB nanosheets (CoMoB) co-catalyst modified carbon nitride with dual moiety defects (CN-TH3/3) Schottky junction photocatalyst is designed for photocatalytic nitrogen reduction reaction (NRR). The photocatalytic nitrogen reduction rate of the optimized CoMoB/CN-TH3/3 photocatalyst is 4.81 mM·g-1·h-1, which is 6.2 and 2.2 times higher than carbon nitride (CN) (0.78 mM·g-1·h-1) and CN-TH3/3 (2.21 mM·g-1·h-1), respectively. The excellent photocatalytic NRR performance is ascribed not only to the introduction of dual moiety defects (cyano and cyanamide groups) that extends the visible light absorption range and promotes exciton polarization dissociation, but also to the formation of interfacial electric field between CoMoB and CN-TH3/3, which effectively facilitates the interfacial charge transfer. Thus, the synergistic interaction between CN-TH3/3 and CoMoB further increases the electron numble of CoMoB active sites, which effectively strengthens the adsorption and activation of N2 and weakens the NN triple bond, thereby enhancing the photocatalytic NRR activity. This work highlights the introduced dual moiety defects and bimetallic CoMoB co-catalyst to synergistically enhance the photocatalytic nitrogen reduction performance.

Nitrogen- and fluorine-doped bimetallic carbide as active and stable oxygen reduction reaction electrocatalyst.

Nitrogen- and fluorine-doped bimetallic carbide composites with graphite matrix (abbreviated as C19Cr7Mo24/NG and C19Cr7Mo24/FG) are synthesized through carbonization at 1300 °C. The C19Cr7Mo24/NG displays an initial half-wave potential (E1/2) of 0.873 V and suffers merely 3 mV decrease in E1/2 within 60,000 CV cycles for oxygen reduction reaction (ORR) in alkaline media. A H2/O2 fuel cell testing system using the C19Cr7Mo24/NG as cathode maintains 95.9% of the initial peak power density (1.08 W cm-2) within 60,000 cycles. The C19Cr7Mo24/FG shows higher ORR activity than the C19Cr7Mo24/NG. The positive and negative charge centers caused by the N or F dopants are the critical reasons to their high activities. While F and bimetallic carbide more favor electron transfer respectively than the N and monometallic carbide. Their excellent stabilities originate from interactions among atoms due to electron transfer and the intrinsic chemical inertness of graphite and bimetallic carbides.

Bridging engineering of polymeric carbon nitride for boosting photocatalytic CO2 reduction.

The inherent electron localized heptazine structure of carbon nitride (CN) derived from intrinsic tertiary N (N3C) bridging structure makes the photogenerated charge separation rather difficult, which severely limits photocatalytic CO2 activity of CN. Therefore, modulation of N3C bridging structure of CN is highly desirable to enhance the charge separation efficiency of CN. Herein, we reported a novel thiophene-bridged CN (BTCN) with intramolecular donor-π-acceptor (D-π-A) systems synthesized by nucleophilic substitution and Schiff base reaction to improve the photogenerated charge separation efficiency. The experimental and density functional theory (DFT) results indicate that this BTCN exhibits a high π-electron delocalization range and enhanced photogenerated charge transfer efficiency, which mainly account for the enhanced photocatalytic activity. The optimal BTCN photocatalyst exhibits enhanced charge separation efficiency and higher photocatalytic CO2 reduction activity with a CO yield of 23.02 µmol·g-1·h-1, which was higher than those of CN and edge-modified CN (ETCN) counterpart. This work highlights the importance of regulation of π-electron delocalization for the design of highly active CN photocatalysts via the rational substitution of N3C bridging structure with π-spacer molecular linkages for photocatalytic CO2 reduction.

Synergistic Coupling of Charge Extraction and Sinking in Cu5FeS4/Ni3S2@NF for Photoassisted Electrocatalytic Oxygen Evolution.

Exploring low-cost and high-performance oxygen evolution reaction (OER) catalysts has attracted great attention due to their crucial role in water splitting. Here, a bifunctional Cu5FeS4/Ni3S2@NF catalyst was in situ formed on a nickel (Ni) foam toward efficient photoassisted electrocatalytic (P-EC) OER, which displays an ultralow overpotential of 260 mV at 30 mA cm-2 in alkaline solution, outperforming most previously reported Ni-based catalysts. It also shows great potential in degradation of antibiotics as an alternative anode reaction to OER owing to the prompt transfer of photogenerated holes. The photocurrent test and transient photovoltage spectroscopy indicate that the synergistic coupling of charge extraction and sinking effects in Cu5FeS4 and Ni3S2 is critical for boosting the OER activity via photoassistance. Electrochemical active surface area and electrochemical impedance spectroscopy tests further prove that the photogenerated electromotive force can effectively compensate the overpotential of OER. This work not only provides a good guidance for integrating photocatalysis and electrocatalysis, but also indicates the key role of synergistic extraction and utilization of photogenerated charge carriers in P-EC.

Synergistic Effects of the Ni3B Cocatalyst and N Vacancy on g-C3N4 for Effectively Enhanced Photocatalytic N2 Fixation.

The photocatalytic fixation of N2 is a promising technology for sustainable production of ammonia, while the unsatisfactory efficiency resulting from the low electron-transfer rate, narrow light absorption range, and limited active sites of the photocatalyst seriously hinder its application. Herein, we designed a noble metal-free Schottky junction photocatalyst constructed by g-C3N4 nanosheets with N vacancies (VN-CN) and metallic Ni3B nanoparticles (Ni3B/VN-CN) for N2 reduction to ammonia. The ammonia yield rate over the optimized Ni3B/VN-CN is 7.68 mM g-1 h-1, which is 6.7 times higher than that of pristine CN (1.15 mM g-1 h-1). The superior photocatalytic N2 fixation performance of Ni3B/VN-CN can be attributed not only to the formation of Schottky junctions between Ni3B and VN-CN, which facilitates the migration and separation of photogenerated electrons, but also to the incorporation of VN into g-C3N4, which enhances visible light absorption and improves electrical conductivity. More importantly, Ni3B nanoparticles can act as the cocatalyst, which provide more active sites for the adsorption and activation of N2, thereby improving the N2 reduction activity. This work provides an effective strategy of designing noble metal-free-based cocatalyst photocatalyst for sustainable and economic N2 fixation.

Mechanical and friction properties of agricultural plastic film during autumn harvest period of cotton in Xinjiang, China.

Agricultural plastic films have caused serious plastic pollution. There are many studies that consider mechanical recycling an appropriate system for the recovery of post-consumption agricultural mulch film. The recovery effect of plastic film depends on the mechanical properties, the level of dirtiness of the post-consumption film, and the recycling process itself. In this study, the mechanical properties of four types of polyethylene plastic films with a thickness of 8, 10, 12, and 10 µm, weather-resistant, commonly used in Xinjiang cotton fields, were tested. As well as the friction coefficient between the film and soil, the cotton stalk, boll shell, and leaf with different moisture contents were measured. Then, the self-propelled straw chopping and residual film recycling combined machine collected the four types of mulch films. The results showed that the longitudinal mechanical properties of the plastic film were greater than the transversal ones, with the exception of the nominal tensile strain at break, and the tensile characteristics of the mulching film covered with soil were greater than those without soil. The dynamic or static friction coefficient between the film and the contact material had a linear relationship with the moisture content of the material. During the recycling operation, the better the mechanical properties of the plastic film, the higher the pick-up rate of the mulch film. The maximum longitudinal tensile force of 12-µm plastic film was 3.42 N, and the nominal tensile strain at break was 303.09%. The pick-up rate reached more than 93% when the 12-µm plastic film was recovered in autumn, which effectively reduced the residue of plastic film coverage in the current year. Moreover, the more soil that was present on the much film, the greater the soil content of the recycled film roll, and the stalk content also increased, but the change was small. The research provides a reference for the mechanical and the friction features of agricultural plastic film in Xinjiang, and provides a theoretical basis for the formulation of standards for film thickness and mechanical properties, as well as the design and optimization of a residual film collecting machine in the cotton field.

NiCoP-nanocubes-decorated CoSe2 nanowire arrays as high-performance electrocatalysts toward oxygen evolution reaction.

Designing effective, robust, and low-cost catalysts for oxygen evolution reaction (OER) is an urgent requirement yet challenging task in water electrolysis. In this study, a NiCoP-nanocubes-decorated CoSe2 nanowires arrays three-dimensional/two-dimensional (3D/2D) electrocatalyst (NiCoP-CoSe2-2) was developed for catalyzing OER via a combined selenylation, co-precipitation, and phosphorization method. The as-obtained NiCoP-CoSe2-2 3D/2D electrocatalyst exhibits a low overpotential of 202 mV at 10 mA cm-2 with a small Tafel slope of 55.6 mV dec-1, which is superior to most of reported CoSe2 and NiCoP-based heterogeneous electrocatalysts. Experimental analyses and density functional theory (DFT) calculations proof that the interfacial coupling and synergy between CoSe2 nanowires and NiCoP nanocubes are not only beneficial to strengthen the charge transfer ability and accelerate reaction kinetics, but also facilitate the optimization of interfacial electronic structure, thereby enhancing the OER property of NiCoP-CoSe2-2. This study offers insights for the investigation and construction of transition metal phosphide/selenide heterogeneous electrocatalyst toward OER in alkaline media and broadens the prospect of industrial applications in energy storage and conversion fields.

Zinc and fluorine ions dual-modulated NiCoP nanoprism array electrocatalysts for efficient water splitting.

Designing efficient, stable, and low-cost bifunctional catalysts for overall water splitting is significant but challenging. In this work, Zn and F ions co-doped NiCoP nanoprism arrays grown directly on nickel foam (Zn/F-NiCoP/NF) was synthesized via hydrothermal method followed by phosphorization treatment. The resultant Zn/F-NiCoP/NF exhibits high electrocatalytic activity towards hydrogen evolution reaction (HER, η10 = 59 mV) and oxygen evolution reaction (OER, η50 = 285 mV). An alkaline electrolyzer using Zn/F-NiCoP/NF as both cathode and anode requires a low cell voltage of 1.568 V at a current density of 10 mA cm-2 with a high long-term stability of up to 40 h, which outperforms many reported Ni,Co-based catalysts. Density functional theory (DFT) calculations proof that simultaneous doping of NiCoP with Zn and F ions provides flexibility to regulate the electronic configuration and downshifts the transition metal d-band center, thereby optimizing adsorption energy between reactants and intermediates, which enhances the HER and OER catalytic activities. This work highlights that cation-anion co-doping strategy is an effective way to develop highly active transition metal phosphides electrocatalyst for water splitting.

Bismuth nanoparticles and oxygen vacancies synergistically modified HNb3O8 nanosheets for enhanced photocatalytic N2 reduction towards NH3.

Due to the high stability of the N2 molecule and the low charge separation efficiency, the photocatalytic reduction of N2 to high-value chemicals (NH3) under mild conditions remains a great challenge. Herein, a composite photocatalyst (Bi/HNb3O8-Vo nanosheets) with Bi nanoparticles modified the HNb3O8-Vo nanosheets are designed for the conversion of N2 into NH3. In this design, the introduction of oxygen vacancies on the catalyst surface facilitates the formation of defective energy levels within the band gap of HNb3O8-Vo NS, which promotes the absorption of visible light, and enhances the charge carrier transport and separation. Bi nanoparticles co-catalyst not only facilitates the separation and migration of photogenerated charges, but also acts as reaction sites to adsorb and activate N2 molecule. Consequently, the optimized 5 % Bi/HNb3O8-Vo photocatalysts show a NH3 yield of 372.7 µmol/L g-1h-1 under full spectral irradiation without sacrificial agent, which is much higher than that of HNb3O8 NS (92.2 µmol/L g-1h-1). This work provides a new way for the design of efficient N2 reduction photocatalysts through the synergistic effect of surface vacancies and metal co-catalysts.

Ni3B as p-Block Element-Modulated Cocatalyst for Efficient Photocatalytic CO2 Reduction.

Due to the multiple electron and proton transfer processes involved, the photogenerated charges are easily recombined during the photocatalytic reduction of CO2, making the generation of the eight-electron product CH4 kinetically more difficult. Herein, Ni3B nanoparticles modulated by p-block element were combined with TiO2 nanosheets to construct a novel Schottky junction photocatalyst (Ni3B/TiO2) for the selective photocatalytic conversion of CO2 to CH4. The formed Ni3B/TiO2 photocatalyst with Schottky junction ensures a transfer pathway of photogenerated electrons from TiO2 to Ni3B, which facilitates the accumulation of electrons on the surface of Ni3B and subsequently improves the activity of photocatalytic CO2 reduction to CH4. The optimized Ni3B/TiO2 Schottky junction shows an improved CH4 yield of 30.03 µmol g-1 h-1, which was much higher than those of TiO2 (1.62 µmol g-1 h-1), NiO/TiO2 (2.44 µmol g-1 h-1), and Ni/TiO2 (4.3 µmol g-1 h-1). This work demonstrated that the introduction of p-block elements can alleviate the scaling relationship effect of pure metal cocatalysts to a certain extent, and the modified Ni3B can be used as a promising new cocatalyst to effectively improve the selective photocatalytic of CO2 to CH4.

Synergizing Cobalt Ruthenium Alloy with Chromium Oxyhydroxide for Highly Efficient Electrocatalytic Water Splitting.

Constructing a coupling interface of multicomponents with different functions is of considerable importance for designing an advanced bifunctional water splitting electrode. Particularly, designing and developing alloy/oxyhydroxide-integrated electrodes have emerged as a tendency yet remain a considerable challenge. In this work, a novel 3D nanostructure electrocatalyst assembled from CoRu nanoalloy and CrOOH nanosheets (denoted as CoRu-CrOOH/NF) was directly grown on nickel foam via a successive hydrothermal method. The unique synergy in CoRu-CrOOH/NF heterostructures is not only conducive to strengthening charge transfer capability and accelerating the reaction kinetics but also favors the redistribution of charge within the interface, thus improving the electrocatalytic performance. In view of the above-mentioned points, the resultant CoRu-CrOOH/NF displays outstanding catalytic performance with overpotentials of 26 and 272 mV at 10 mA cm-2 for hydrogen evolution reaction (HER) and 50 mA cm-2 for oxygen evolution reaction (OER). Remarkably, the symmetrical two-electrode cell using CoRu-CrOOH/NF only acquires 1.47 V at 10 mA cm-2 in 1.0 M KOH, which is superior to many other state-of-the-art overall water-splitting electrocatalysts. This holistic work provides a new insight to designing alloy/oxyhydroxide-integrated electrodes for high-efficiency overall water splitting.

Efficient charge transfer in Co-doped CeO2/graphitic carbon nitride with N vacancies heterojunction for photocatalytic hydrogen evolution.

Photocatalytic hydrogen evolution is a promising and environmentally friendly strategy to prepare renewable energy sources thus addressing the energy crisis and environmental issues, and it is crucial to develop an ideal photocatalytic for highly efficient H2 production. Herein, the Co-doped CeO2 decorated on graphitic carbon nitride with N vacancies (NVs) heterostructure photocatalyst (Co-CeO2/DCN) is prepared via a simple self-assembly method. Due to the extended light absorption range, and efficient charge separation and migration derived from the introduction of NVs and the heterojunction structure, the photocatalytic activity of the Co-CeO2/DCN is largely promoted. The optimal sample 20-Co-CeO2/DCN shows a high H2 evolution rate of 1077.02 µmol g-1h-1 (λ > 400 nm), which is 113 and 33 times higher than the bare bulk graphitic carbon nitride (BCN) and CeO2, respectively. This work will provide a new strategy to develop high-performance photocatalysts using defect engineering and heterojunction engineering for H2 evolution.

Ru-doping modulated cobalt phosphide nanoarrays as efficient electrocatalyst for hydrogen evolution rection.

Electrochemical water splitting is regarded as a prospective means for H2 production. The lack of efficient active sites and the sluggish kinetics in alkaline media remain the major obstacles for hydrogen evolution reaction (HER). Herein, a rational construction of Ru-doped cobalt phosphide leaf-like nanoarrays supported on carbon cloth (Ru-CoP NAs) was designed via a MOF-derived route and subsequent phosphating treatment for accelerating HER in the alkaline. The unique hierarchical structure is conductive to exposing more active sites and accelerating the diffusion of electrolyte and the release of H2 bubble. The optimized Ru-CoP-2.5 NAs exhibits a small overpotential of 52 mV to drive 10 mA cm-2 for HER and a low Tafel slope of 39.7 mV dec-1 in 1 M KOH, which outperforms most of other reported CoP-based electrocatalysts. Furthermore, density functional theory (DFT) calculations unveil that Ru dopants can modulate the electron environment around pure CoP and optimize the adsorption energy of H*, accelerating the reaction kinetics. This work provides an insight to promote the electrocatalytic activity of metal phosphide for hydrogen production.

Metal-Organic Framework-Derived Three-Dimensional Macropore Nitrogen-Doped Carbon Frameworks Decorated with Ultrafine Ru-Based Nanoparticles for Overall Water Splitting.

Hydrogen energy with the advantages of green, sustainability, and high energy density has been considered as an alternative to fossil fuel energy. Water electrolysis to produce hydrogen is a promising energy conversion technology but limited to the large overpotential; thus, a highly efficient electrocatalyst is urgently needed. Herein, Ru-based electrocatalysts including an ultrathin Ru/three-dimensional (3D) macropore N-doped carbon framework (Ru/3DMNC) and ultrathin RuO2/3D macropore N-doped carbon framework (RuO2/3DMNC) are first prepared using a Zn-centered metal-organic framework (MOF, ZIF-8) as the precursor. The ultrathin 3D macropore framework structure together with N doping endows the as-synthesized Ru-based electrocatalysts with abundant exposed catalytic active sites, good electroconductivity, and excellent electron/mass transport, accomplishing improved activities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. The Ru/3DMNC and RuO2/3DMNC present low overpotentials of 50.96 and 216.74 mV to reach a current density of 10 mA cm-2. Moreover, the overall water splitting device constructed by Ru/3DMNC and RuO2/3DMNC as the cathode and anode catalysts, respectively, affords a current density of 10 mA cm-2 only at 1.51 V, which is superior to the Pt/C||RuO2 cell (1.573 V). This work provides a rational strategy to design and construct the efficient framework structure electrocatalysts for water splitting using MOFs as the precursor.

Carbon vacancy-mediated exciton dissociation in Ti3C2Tx/g-C3N4 Schottky junctions for efficient photoreduction of CO2.

Earth-abundant g-C3N4 is a promising photocatalyst for CO2 reduction, but its practical application is severely limited by the excitonic effect of g-C3N4 derived from strong binding energy and lack of electron-enriched active sites. Herein, we design a novel 2D/2D Schottky junction photocatalysts comprising of Ti3C2Tx-modified defective g-C3N4 nanosheets with carbon vacancy (denoted as Ti3C2Tx/Vc-CN) by a self-assembly method. The carbon vacancies in g-C3N4 promote exciton dissociation into free charge, while the formed Schottky junctions between Ti3C2Tx and Vc-CN further enables a directional charge transfer, thus providing an electron-rich catalytic surface for the CO2 reduction. Thanks to the synergy of promoted exciton dissociation and directional electron transfer, the optimal 20% Ti3C2Tx/Vc-CN display a high CO evolution rate of 20.54 µmol·g-1·h-1 under visible light irradiation, which is 7.4 times higher than that of bare CN. This work highlights the synergy of the promoted exciton dissociation and directional electron transfer in the activity enhancement of photocatalytic CO2 reduction.

Synergistically Coupled CoMo/CoMoP Electrocatalyst for Highly Efficient and Stable Overall Water Splitting.

Finding reservoir-rich and efficient bifunctional electrocatalysts for water splitting is key to further sustainable energy development. Transition metal phosphides (TMPs) are extensively exploited as effective electrocatalysts, but the construction of strong coupling interfaces to improve catalytic performance by simple methods is still a bottleneck. Here, we designed and prepared a novel heterostructure electrocatalyst composed of cobalt-molybdenum (CoMo) alloy particles integrated with CoMoP nanosheets via the method of template-assisted conversion, followed by electrodeposition. Thanks to the strong interfacial coupling and synergistic effect between CoMo alloy particles and CoMoP nanosheets, the prepared CoMo/CoMoP/NF shows outstanding activity with overpotentials of only 29 mV for the hydrogen evolution reaction (HER) and 246 mV for the oxygen evolution reaction (OER) in 1 M KOH at a current density of 10 mA cm-2. Furthermore, the assembled CoMo/CoMoP || CoMo/CoMoP electrode can attain 10 mA cm-2 with a low battery voltage of 1.54 V. This study offers a valuable reference to the construction of bimetallic alloy/bimetallic phosphide heterostructure electrocatalysts, which applies to the large-scale application of electrocatalytic energy conversion technology.

Anchoring RuSe2 on CoSe2 nanoarrays as a hybrid catalyst for efficient and robust oxygen evolution reaction.

Interface engineering is an effective strategy to regulate the oxygen adsorption strength and accelerate the kinetics of oxygen evolution reaction (OER) catalyst by using the synergistic effect and electronic coupling between different metals. However, the design and demonstration of efficient and strongly coupled interfaces remains a bottleneck in the progress of efficient and durable OER catalysts. Herein, we designedly anchored RuSe2 nanoparticles to CoSe2 nanosheet arrays support on nickel foam (NF) to fabricate a RuSe2-CoSe2 nanosheet arrays with robust structure and strong electron coupling. Co-MOF was used as a template to conduce Ru ion exchange and then the precursor was selenized at low temperature to obtain RuSe2 modified CoSe2 nanosheet arrays. Thanks to the strong electron coupling between Ru with Co and the unique nanoarray structure, RuSe2-CoSe2 exhibits excellent OER performance with ultra-low overpotential of 200 mV at current density of 10 mA cm-2, and the performance did not degrade significantly during 100 h of continuous operation. Furthermore, the assembledRuSe2-CoSe2 (+)//Pt/C (-) can reach 50 mA cm-2 in a two-electrode system with a low battery voltage of 1.61 V, which is superior to the commercial RuO2 (+)//Pt/C (-) (1.79 V) electrode. This work provides an effective avenue for the design of highly active and durable electrocatalysts.

Photocatalytic reduction of CO2 into CH4 over Ru-doped TiO2: Synergy of Ru and oxygen vacancies.

Photocatalytic conversion of CO2 and H2O into CH4 is an intriguing approach to achieve solar energy utilization and CO2 conversion, yet remains challenging in conversion efficiency. In this study, we present a synthesis of defected TiO2 nanocrystal with oxygen vacancies (Vo) by a facile Ru doping-induced strategy under hydrothermal condition. The synergistic effect of Ru and oxygen vacancies contributed to the enhanced photocatalytic reduction of CO2 toward CH4. Oxygen vacancies and doped Ru not only can synergistically promote the separation of photogenerated carriers, but also promote the CO2 adsorption, thus enhancing the photocatalytic activities. The optimal Ru-doped TiO2 (denoted as 1% Ru-TiO2-x) exhibited a remarkable enhanced photocatalytic performance with a CH4 yield of 31.63 µmol·g-1·h-1, which is significantly higher than Ru-TiO2 and TiO2-x counterparts. This study systematically investigates the multiple roles of Ru in CO2 reduction and provides new insights for the construction of metal oxide photocatalysts with oxygen vacancies by simple doping of metal ions.

Stable and enhanced electrochemical performance based on hierarchical core-shell structure of CoMn2O4@Ni3S2electrode for hybrid supercapacitor.

Herein, accessible and low-cost CoMn2O4@Ni3S2core-shell nanoneedle arrays have been prepared via a two-step approach comprised with hydrothermal-calcination and electrochemical deposition procedures, successfully. In the beginning, CoMn2O4nanoneedle arrays took root on Ni foam to form the core skeleton and subsequently, hierarchical Ni3S2nanosheets uniformly overlaid on the surface of CoMn2O4nanoneedles shaping the shell structure. This CoMn2O4@Ni3S2material was measured directly as supercapacitor electrode and presented high specific capacity of 192.2 mAh g-1with current density of 1 A g-1. Besides, the electrode delivered outstanding cyclical stability as the capacity retention attained 90.2% after charge-discharge measurement at a large current density of 10 A g-1for 10 000 cycles. Furthermore, a hybrid supercapacitor assembled by CoMn2O4@Ni3S2cathode and activated carbon anode represented a high energy density of 51.2 Wh kg-1with the power density of 1030.0 W kg-1. This work shows a facile and inexpensive procedure to design high-performance and strong-stability supercapacitor electrodes.

Synergistic Integration of AuCu Co-Catalyst with Oxygen Vacancies on TiO2 for Efficient Photocatalytic Conversion of CO2 to CH4.

Photocatalytic reduction of CO2 toward eight-electron CH4 product with simultaneously high conversion efficiency and selectivity remains great challenging owing to the sluggish charge separation and transfer kinetics and lack of active sites for the adsorption and activation of reactants. Herein, a defective TiO2 nanosheet photocatalyst simultaneously equipped with AuCu alloy co-catalyst and oxygen vacancies (AuCu-TiO2-x NSs) was rationally designed and fabricated for the selective conversion of CO2 into CH4. The experimental results demonstrated that the AuCu alloy co-catalyst not only effectively promotes the separation of photogenerated electron-hole pairs but also acts as synergistic active sites for the reduction of CO2. The oxygen vacancies in TiO2 contribute to the separation of charge carriers and, more importantly, promote the oxidation of H2O, thus providing rich protons to promote the deep reduction of CO2 to CH4. Consequently, the optimal AuCu-TiO2-x nanosheets (NSs) photocatalyst achieves a CO2 reduction selectivity toward CH4 up to 90.55%, significantly higher than those of TiO2-x NSs (31.82%), Au-TiO2-x NSs (38.74%), and Cu-TiO2-x NSs (66.11%). Furthermore, the CH4 evolution rate over the AuCu-TiO2-x NSs reaches 22.47 µmol·g-1·h-1, which is nearly twice that of AuCu-TiO2 NSs (12.10 µmol·g-1·h-1). This research presents a unique insight into the design and synthesis of photocatalyst with oxygen vacancies and alloy metals as the co-catalyst for the highly selective deep reduction of CO2.