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Made available in DSpace on 2019-10-04T12:37:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) FAPITEC Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Carbon-supported Pd, Au@Pd core-shell and Au1-xPdx-alloyed nanoparticles were prepared by a chemical reduction method and characterized by different experimental techniques, including X-ray powder diffraction, transmission electron microscopy, scanning-transmission electron microscopy using bright-field and high-angle annular dark field detectors and X-ray energy dispersive spectroscopy. The catalytic mass activity toward ethanol oxidation was assessed by cyclic voltammetry and chronoamperometry at room temperature. The measurements showed that the addition of Au enhances remarkably the electrocatalytic activity of the material, due to the bifunctional effect of Au1-xPd/C alloys, and the synergetic effect on Au@Pd/C, resulting in a dissolution resistance of core-shell catalysts at potentials of 1.5 V versus reversible hydrogen electrode. In situ Fourier transform infrared spectroscopy measurements showed that the mechanism for ethanol oxidation depends on the electrocatalyst structure and morphology. Acetate was identified as the main product of ethanol electro-oxidation on the studied electrocatalysts. However, the presence of a core-shell structure on Au@Pd/C resulted in enhanced ethanol oxidation selectivity toward CO2. The improvement of activity is attributed to the interaction between Pd shell and Au core. Inst Technol & Res, Lab Electrochem & Nanotechnol, BR-49032490 Aracaju, SE, Brazil Univ Tiradentes, Proc Engn Postgrad Program, BR-49032490 Aracaju, SE, Brazil Univ Fed Sergipe, Dept Phys, Campus Itabaiana,Ave Marechal Rondon, BR-49032490 Aracaju, SE, Brazil Univ Estadual Paulista, Dept Phys Chem, Inst Chem, Campus Araraquara,Ave Araraquara Jau, Araraquara, SP, Brazil Univ Fed ABC, Ctr Engn Modeling & Appl Social Sci, Ave Estados 5001, Santo Andre, SP, Brazil Univ Estadual Paulista, Dept Phys Chem, Inst Chem, Campus Araraquara,Ave Araraquara Jau, Araraquara, SP, Brazil CNPq: 303630/2012-4 CNPq: 474261/2013-1 CNPq: 407274/2013-8 CNPq: 402243/2012-9 CNPq: 400443/2013-9 CNPq: 310282/2013-6 CAPES: 001

Nitrogen doped carbon nanotubes (NCNTs) with high concentration of pyridinic N sites (62.3% of all nitrogen) were prepared by pyrolysis of phenathroline heterocycle precursor, and they can reduce CO2 to CO with high selectivity and stability. Faradaic efficiency of CO maintained >94.5% between −0.6 to −0.9 V vs the reversible hydrogen electrode (RHE), and the CO current density was as high as 20.2 mA cm−2. Moreover, during 40 h electrolysis at −0.8 V, Faradic efficiency for CO was stable at 95%. The high performance came from rich concentrations of pyridine N sites in NCNTs, serving as the active sites for catalysis. Furthermore, gas phase CO2 electrolysis showed nearly 100% Faradic efficiency for CO, suggesting that the NCNT can maximize the CO2 reduction efficiency and hydrogen evolution was suppressed completely.

Copper vanadates are considered as one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting owing to their narrow bandgap, stoichiometry-dependent optical and electrical properties, and high stability. However, for technological applications, it is imperative to develop stoichiometrically and structurally tuned copper vanadates for improved performance. In this study, we developed a facile and one-step hydrothermal method for the synthesis of Cu2V2O7 nanoplates, Cu5V2O10 nanorods, and Cu11V6O26 micropillars on a fluorine-doped tin oxide substrate without using a seed layer. The presence of urea during the hydrothermal synthesis significantly affected the film formation and morphology of the copper vanadates. The crystallographic, chemical, and electrochemical properties of the synthesized copper vanadates were investigated. The optimized Cu2V2O7, Cu5V2O10, and Cu11V6O26 electrodes exhibited the highest photocurrent densities of ˜0.41, 0.27, and 0.076 mA cm−2 (at 1.23 V vs. reversible hydrogen electrode under 1-sun illumination) and incident photon to current efficiency values of ˜24%, 18%, and 7.5% (at 300 nm), respectively. The band edge positions of Cu2V2O7, Cu5V2O10, and Cu11V6O26 were estimated on the basis of the spectroscopic and electrochemical results. The synthesis scheme and valuable insights provided in this work can be used for the development of chemically and morphologically optimized copper vanadates for efficient PEC water splitting.

An advanced trifunctional electrocatalyst based on a series of composites composed of TiO2-encapsulated carbon-nitride (CNx) (denoted as TiO2C@CNx) is developed, which is derived from the Ti3C2Tx and melamine–cyanuric acid calcinated at different temperatures. Among the series of TiO2C@CNx nanosheets, the TiO2C@CNx,950 (obtained by calcination at 950 °C) hybrid exhibits robust trifunctional electrocatalytic activity toward the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) by combining the excellent electrochemical activity of the graphene-like nanostructure and the high electrocatalytic performances of TiO2 nanoparticles. When TiO2C@CNx,950 is used as the electrocatalyst for water splitting, a current density of 10 mA cm−2 (Ej = 10) is achieved at a low cell voltage of 1.50 V vs. reversible hydrogen electrode. Meanwhile, the overall oxygen activity of the TiO2C@CNx,950 exhibits good reversible oxygen reaction, giving a small potential difference between the Ej = 10 for OER and the half-wave potential for ORR (0.75 V). Moreover, a simply equipped Zn-air battery is assembled using a homemade cathode, showing open-circuit potential of 1.344 V, which also can supplied an electrical power and produced H2 at the cathode and O2 at the anode. Consequently, this work can pave a path for developing multifunctional electrocatalysts for water spitting and liquid Zn–air battery.

Achieving a high photocatalytic activity toward photoelectrochemical (PEC) water splitting has become a formidable challenge for titanium oxide (TiO2) owing to its poor photoresponse to visible light and low electrical conductivity. Herein, we report the first demonstration of nonmetal TiN as a plasmonic booster to significantly enhancing the PEC water splitting performance of TiO2. A unique multiscaled architecture organized by interweaving hollow microfiber monolith and hierarchical TiN/N-TiO2 nanorod arrays is fabricated by a facile seamless nitridation process. The conductive TiN not only affords plasmon resonance on the N-TiO2 to enable high photoactivity in a broadband UV–vis light region, but also assists in the charge generation-separation-transportation-injection efficiency of TiO2 for enhanced water oxidation kinetics. The TiN/N-TiO2 heterostructure manifests an unprecedented high and durable photocurrent density of 3.12 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode (RHE)) under standard AM 1.5 G illumination and substantiates an outstanding visible-light-driven photocurrent density of 1.63 mA cm−2 without the use of any hole scavenger and cocatalysts. This study will enrich the fundamental understanding of nonmetal plasmonic effect in and beyond the field of PEC water splitting.

BiVO4 is one of the most promising semiconductors for photoelectrochemical water splitting. BiVO4 is, however, limited by poor charge separation and slow oxygen evolution dynamics, for which surface modification with oxygen evolution catalysts (OECs) becomes indispensable. Among many OECs, Prussian blue type coordination polymers have lately attracted an escalating research interest attributable to their low cost, chemical robustness and easy synthesis using nontoxic earth-abundant elements. In this study, we report a simple method for efficient surface modification of Zr-doped BiVO4 nanostructured electrodes with an amorphous Ni-Fe based Prussian blue (NiFePB) polymer. The method resulted in a remarkable 10-fold enhancement of photocurrent (3.23 mAcm−2 at 1.23 V versus the reversible hydrogen electrode RHE) and a low onset potential of 0.208 V versus RHE, which are both records for Prussian blue (PB) type materials. Our coating method results in a (Zr)BiVO4/NiFePB core-shell structure, in which a 10–15 nm NiFePB shell makes a superior conformal coating with complete coverage on the (Zr)BiVO4 nanoparticles. The high conformity and amorphous nature of the coating are believed to be key features for the high photocatalytic activity and for a high photocorrosion resistance of the photoanodes during > 50 h of AM1.5 G solar illumination. Our method illustrates the large potential of Prussian blue type materials, when properly coated, as efficient and highly stable OECs.

A photoactive amine-functionalized Ti metal-organic framework (MOF) (MIL(125)-NH2(Ti)) layer is uniformly coated on vertically ordered TiO2 nanorods (NRs) via a facile hydrothermal reaction, and the performance of the heterojunction photoanode in photoelectrochemical (PEC) water splitting is studied. The photocurrent density of the MIL(125)-NH2/TiO2 NRs reaches 1.63 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode under AM 1.5 G simulated sunlight illumination, which is ∼2.7 times higher than that of pristine TiO2 NRs. The incident photon-to-electron conversion efficiency of the MIL(125)-NH2/TiO2 NRs improves significantly at λmax = 340 nm, implying the promotion of water oxidation through efficient light absorption and charge separation. The enhancement of the PEC activity in the TiO2 NRs caused by an MIL(125)-NH2 coating is discussed in relation to the surface area and elongated configuration of the TiO2 NRs, the band gap of MIL(125)-NH2(Ti), and the type (II) heterojunction. This study demonstrates the rational design of heterojunctions between the semiconductor and the MOF, which paves the way for new facile and general approaches to achieve a high efficiency in water splitting.

Well-defined porous heteronanostructures with broad light absorption range and efficient charge transfer are the key challenges towards developing efficient photoanodes for photoelectrochemical (PEC) water splitting. Herein, we reported a facile template and continuous ion exchange method to fabricate three-dimensional ordered mesoporous (3DOM) ZnO/ZnxCd1-xSe inverse opal with binder-free heterojunction interfaces on F-doped SnO2 glass. The heteroepitaxial growth of ZnxCd1-xSe shell layer on ZnO inverse opal skeleton surface provided favorable type-II band alignment, low interfacial resistance, and high visible light absorption. As expected, the optimized 3DOM ZnO/ZnxCd1-xSe inverse opal achieved a significant saturated photocurrent density of 24.76 mA cm−2 at 1.23 V versus a reversible hydrogen electrode (RHE) in 0.25 M Na2S and 0.35 M Na2SO3 aqueous solution under AM 1.5 G simulated solar light irradiation (100 mW cm-2), which is 25 times higher than that of the pristine ZnO (0.99 mA cm−2 at 1.23 V versus RHE) photoanode. The maximum photoconversion efficiency reached 10.64% for the optimized 3DOM ZnO/ZnxCd1-xSe inverse opal at an applied potential of 0.52 V versus RHE, an about 22.63 times increase relative to that of the pristine ZnO inverse opal (0.47% at 0.61 V versus RHE). In addition, the photostability of the optimized 3DOM ZnO/ZnxCd1-xSe inverse opal photoanode was also greatly improved in the electrolyte solution, 82.6% initial value was maintained even after 3000 s continuous light illumination without any protective coating layer. Such prominent PEC performances of the as-prepared 3DOM ZnO/ZnxCd1-xSe inverse opal can be ascribed to the improved visible light harvesting and enhanced charge separation/collection efficiency. This work provides a fundamental insight to design the efficient photoanode for high performance water splitting.

While converting carbon dioxide (CO2) into value-added carbon products by electrolyzing offers a promising approach to mitigate global warming and store energy, poor selectivity and stability of catalysts still impede this conversion. Single-atom catalyst exhibits exceptional selectivity for CO2 electroreduction reaction in response to inhibiting hydrogen evolution reaction (HER), which is the major obstacle to the development of CO2 reduction. Herein we introduce a facile approach to obtain Ni-Nx sites encapsulating into carbon nanotubes with a nickel loading as high as 6.63 wt%. This catalyst exhibits high Faradaic efficiency approximately 95% for CO2 electroreduction to carbon monoxide (CO) in the wide potential range from −0.7 to −1.0 V, and the current density reaches 57.1 mA cm−2 at −1.0 V versus a reversible hydrogen electrode (RHE). Experiments and characterization results demonstrate that nickel chemical state and content play a vital role for CO2 electrocatalytic performance. Moreover, the simplifying of the synthesis may shed a new light on design single atom catalysts of electrochemistry in addition to CO2 reduction.

The development of efficient and durable non-precious cathode catalyst have been received the great interest to replace the commercial noble catalysts, thereby minimizing the overall cost of polymer electrolyte membrane fuel cells. We describe the synthesis of self-redox CeO2 supported Co in nitrogen-doped carbon nanorods (Co-CeO2/N-CNR) by the electro-spun method, and introduced as an enhanced bifunctional catalyst for oxygen reduction (ORR) as well as evolution (OER) reactions by the synergistic effect of oxygen buffer CeO2 with metallic Co. Systematic structural and optical studies confirm the formation and uniform distribution of CeO2 and Co particles in N-CNR. The X-ray photoelectron spectroscopy analysis of Co-CeO2/N-CNR reveals that the presence of Co2+ and multiple valence states of ceria (Ce4+ and Ce3+). The shift in binding energies of Co2+ and Ce3+ states confirm the possible interaction for the cooperative effect of ceria and cobalt during ORR and OER, and electrode stability improvement as well. The Co-CeO2/N-CNR catalyst shows the enhanced oxygen electrode potential of 0.84 V (versus reversible hydrogen electrode), which is 100 and 196 mV lower than Co/N-CNR and Pt/C, respectively, including the improved stability.

Enhancing the separation and transfer of photogenerated carriers is critical factor for increasing the light to chemical energy conversion efficiencies. Here, we exposed {001} and {010} facets on [100] oriented Ta3N5 cuboid, creating 18.6 times enhancement in photocatalytic reduction of CO2 to CH4 and a 0.42 VRHE (reference to reversible hydrogen electrode) photocurrent onset potential for photoelectrochemical water splitting. The pronounced photocatalytic performance is mainly attributed to that surface electric field from large surface band bending of the {001} with high work function drives electrons and holes to {010} and {001}, respectively, achieving a spatial charge separation. Differing to a main effect in charge separation and transfer for the traditional junction electric field region at buried heterjunction or homojunction interface, a surface electric field region is a place where charges separate and transfer efficiently and also the place for the catalytic reactions to occur.

In photoelectrochemical (PEC) water splitting systems, crucial obstacles limiting their performance are poor charge carrier dynamics and high recombination rate of photoexcited electron hole pairs. Here, we report that this issue can be alleviated by engineering a hybrid-junction that is composed of homo- and hetero- junctions. This strategy is performed by facile hand-spraying MoS2 over the surface of a anatase/rutile homo-junction TiO2 film on the Ti substrate to further form a hybrid-junction photocathode. By applying this photocathode into PEC reactor, enhanced catalytic activity is achieved under visible light (AM1.5 illumination of 300 W/m2) with hydrogen evolution reaction (HER) potential of −114 mV versus reversible hydrogen electrode (RHE) at 10 mA/cm2 and long-term stability of more than 10 times improvement comparing to ordinary electrode without the introduciton of hybrid-junction. The hybrid-junction that effectively regulates charge separation and transfer pathways is proven to be responsible for the enhanced activity. As an novel exploration, this hybrid-junction system comprising of low-cost, efficient charge separation and transfer, and visible light responsivity offers a new path for relative materials to boost their PEC performance.

The photoelectrochemical performance of photoanode depends significantly on the surface properties. Enormous efforts have been spent on fabricating photoanode with exposure of high-activity facets. However, precise control of the Ta3N5 facet exposure is still highly challenging, due to its harsh fabrication condition. In this study, it was found that Ta3N5 polyhedron can be grew through a bottom-up growth process in molten salt. Molten salt media in a semi-closed reactor provides a steady growth environment so that the Ta3N5 growth units are able to assemble in thermodynamically and kinetically favorable way. The preferential exposed facets are determined to be {001} facets. Due to the stronger built-in electric field on {001} facets and the small effective mass of hole along the [001] axis, an onset potential of 0.6 V versus reversible hydrogen electrode (RHE) and a photocurrent of 5.6 mA cm−2 at 1.23 versus RHE have been achieved. Our findings may open an avenue to grow the nitride or oxynitride semiconductor crystals with desired structures for achieving efficient solar energy conversion and storage.

Developing durable Si-based photoelectrochemical hydrogen evolution reaction in alkaline media is attracting attention in device-level water splitting, but still faces a trade-off between the alkalic corrosion resistance and light transmission for Si photocathodes. Herein, a synergetic strategy is proposed to employ an anti-reflective Co-P film cocatalyst modulated via self-assembly of protective-layer WSx onto Si photocathode. The controllable WSx thin-film efficiently ensures the excellent anti-alkali corrosion of Si semiconductors, and serves as an appropriate nucleation base to modulate the structure of Co-P cocatalyst to possess anti-reflection. The optimal Co-P/WSx/Si photocathode exhibits an onset potential of + 0.47 V vs. reversible hydrogen electrode (VRHE), a photocurrent density of − 25.1 mA cm−2 at 0 VRHE, and superior durability of up to 300 h at 0 VRHE in 1.0 M KOH electrolyte. These findings offer a facile and effective approach for the further development of durable Si-based photoelectrochemical devices.

Tuning surface properties of electrocatalysts for sustainable electrocatalytic nitrogen reduction reaction (NRR) with high selectivity and activity is highly demanded but still lacks fundamental understanding and modulation methods. Herein, we report the transformation of hydrogen evolution reaction (HER)-favorable cobalt phosphide (CoP) to NRR-favorable electrocatalyst via modulation of surface properties. The oxidized CoP particles encapsulated in carbon nanotubes (O-CoP/CNT) exhibits a high NH3 yield of 39.58 µg h−1 mg-1 cat as well as high Faradaic efficiency (FE) of 19.4% at −0.5 V vs. reversible hydrogen electrode (RHE), which is confirmed by 15N2 isotope-labeling tests. In-situ Raman spectra identify that N2 molecules are preferentially captured by Co ions, while the surface-adsorbed H+ are gradually eliminated. The hydrophobic surface of CNT can limit the contact of protons with the catalyst surface to inhibit HER, and the formation of hydrogen bond facilitates a more efficient NRR process. The surface modulation effects are confirmed by density functional theory calculations.

Electrochemical reduction of CO2 (CO2RR) to value-added chemicals is a feasible strategy to build a carbon neutral society and store energy. However, the sluggish kinetics of CO2RR accompanied by competing hydrogen evolution reaction (HER) makes the practical application of this process very challenging. Herein, we construct a Ni/Ni3ZnC0.7 heterostructured catalyst wrapped in porous N-doped carbon nanofibers via a facile electrospinning strategy for CO2RR. Remarkably, the as-prepared Ni/Ni3ZnC0.7 catalyst exhibits a high selectivity of 91.5% toward CO, a superior CO partial current density of 11 mA cm−2 at −0.8 V versus the reversible hydrogen electrode (vs. RHE) and maintaining 93.4% of its initial selectivity after 45 h of continuous electrolysis. The calculation results of density functional theory (DFT) show that the heterostructure of Ni/Ni3ZnC0.7 catalyst is beneficial to the formation of *COOH and enhances the efficiency of electrocatalytic CO2 conversion.

It is a challenging task to overcomes the bottleneck of N2 adsorption and activation in N2 reduction reaction (NRR). Regulating the catalyst surface electronic state is treated as a potential strategy to prevail over the barrier. Here, Incorporating Fe as a dopant in the TiO2 nanoparticles can generate oxygen vacancies and dopant energy levels, promoting the adsorption and activation of N2 molecules. F surface modification induces Fe (III) in the high spin state and upshifts the dopant energy level. That facilitates Fe 3d electrons backdonation to N 1πg* orbital promotes the activation of N2 molecule and reduces the limiting potential of NRR. Therefore, F-Fe: TiO2 electrocatalyst achieved the highest Faradaic efficiency and maximum NH3 production rate of 27.67% and 27.86 µg h 1 mgcat. 1 at −0.5 V v.s. reversible hydrogen electrode. This work provides deep insights into the design surface electronic state of catalyst toward efficient N2 to NH3 conversion.

A tin-modified copper foam for the efficient and selective reduction of CO2 to CO is reported. We employ a cost-efficient electrodeposition route to form a three-dimensional porous dendrite architecture, in which each dendrite possesses a copper core and a copper oxide/tin oxide shell. The sparse tin species on the electrode surface play a key role to achieve excellent faradaic efficiencies for CO formation with a maximum value of 94%. We demonstrate high CO partial current densities of 4.7 mA cm−2 and 7.9 mA cm−2 at applied potentials of -0.8 V and -1.1 V vs. the reversible hydrogen electrode, respectively. The high activity for electrochemical CO2 reduction is attributed to the unique hierarchical porous structure, which offers abundant electrochemically active sites and facilitates mass transport.

Here we report a p-Si photocathode decorated with nickel complex Ni(TEOA)2Cl2 (Ni1) in acidic aqueous solution (pH = 0.3) for photoelectrochemical (PEC) H2 generation. Compared to bare p-Si, p-Si/Ni1 electrode exhibits significantly enhanced PEC performance, with higher cathodic photocurrent and exceptional lower onset potential. A relatively high photocurrent density of 5.57 mA/cm2 was obtained at 0.0 V vs. reversible hydrogen electrode (RHE) under simulated 1 Sun illumination, which is even comparable to that of p-Si/Pt. Furthermore, the highly active p-Si/Ni1 electrode shows a remarkable stability over 24 h. The possible catalysis mechanism of Ni1 for p-Si in the PEC H2 evolution process was also proposed in detail. The excellent PEC performance should be attributed to the Ni1 engineered p-Si/electrolyte interface energetics and the Ni1 catalyzed water reduction reaction, leading to robust hydrogen generation and excellent PEC stability. The present study made a deep insight into the engineered interface charge transfer and catalyst-driven surface water reduction processes at the semiconductor/electrolyte interface, which could provide some referable guidelines for fabricating highly efficient PEC system for solar H2 generation from the viewpoint of interface energetics engineering with metal complexes.

Regulating electronic structure of electrocatalysts to optimize reactant adsorption on the catalyst surface is a crucial tactic to boost catalytic activity in electrocatalysis. Herein, a novel KCu7S4/CuO interfacial structure is well constructed to induce the formation of localized charge region to optimize the adsorption properties of active intermediates at the interface to promote CO2 electroreduction. The catalyst of interfacial catalyst delivered boosted CO2RR activity and selectivity toward formate with a Faraday efficiency (FE) of 71.0 % and a decent current density of 7.56 mA cm−2 at a moderate potential of -0.9 V (versus reversible hydrogen electrode) as well as a good durability. Theoretical calculations unveiled that the enhanced CO2RR activity and formate selectivity could be attributed to the strengthened CO2* adsorption in the initial step, the increased adsorption of the key intermediates OCHO*, and the weakened H* adsorption via the localized positive charge region induced by charge redistribution at interface.

As the rapid development of oxygen evolution catalysts (OECs) for photoanodes, the issue of charge transfer at the interface of OEC and semiconductor, which becomes the key challenge for the photoelectrochemical (PEC) efficiency, has been rarely addressed and should be taken seriously. Herein, a novel charge transfer system for PEC water oxidation is designed by inserting MXene nanosheets (MNs) between α-Fe2O3 and OEC. In this system, MNs act as the hole transfer mediators to efficiently suppress the interfacial charge recombination owing to the high hole mobility of MNs and the formation of built-in electric field at the MNs/α-Fe2O3 junction. Meanwhile, the OEC layers, in turn, can protect the MNs from oxidation to achieve prominent stability. The optimized photoanode of Co-Pi/MNs/α-Fe2O3 can achieve a remarkable photocurrent density, up to 3.20 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 G illumination. An impressive cathodic onset potential shift of ∼250 mV is obtained on Co-Pi/MNs/α-Fe2O3 compared with the pristine α-Fe2O3. Furthermore, this strategy is also applicable to other photoanode materials, such as BiVO4, WO3 and ZnO, verifying the versatility by utilizing the MNs as hole transfer mediators for efficient photogenerated charge separation to enhance the PEC water oxidation.

Single-atom cobalt-nitrogen-carbon (Co-N-C) has emerged as one of the most promising electrocatalysts for the oxygen reduction reaction (ORR) as it has the utmost atomic utilization efficiency and may avoid possible Fenton reactions. Herein, we report dual carbon-supported single-atom cobalt with the unusual Co-N coordination number of three (Co-N3-C) as an efficient catalyst for the ORR. The combination of experiments and density functional theory calculations reveal that the Co-N3-C would experience an activation process and be favorable to lowering the energy barriers of the intermediates, leading to accelerated reaction kinetics. The as-prepared Co-N3-C catalyst exhibited unprecedented ORR activity with a half-wave potential of 0.891 V versus reversible hydrogen electrode and outstanding stability under alkaline conditions, not only outperforming the previously reported Co-based catalysts but also surpassing state-of-the-art Pt/C catalyst. The current work may provide a new insight into the engineering of the single-atom coordination environment to improve the catalytic activity.

Electrocatalytic nitrogen reduction reaction is increasingly deemed as a promising route for massive ammonia synthesis. Herein, hollow bimetallic CoFe2O4 nanocube derived from prussian blue analogue is elaborately wrapped by thin carbon layer and modified by rich oxygen vacancies, achieving splendid ammonia yield rate of 30.97 μg h−1 mgcat.−1 and Faradaic efficiency of 11.65 % at −0.4 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, C@CoFe2O4-x nanocube can withstand long-term and repetitive electrolysis without obvious structure collapse, constituent change and activity decay. The prominent activity is strongly associated with improved nitrogen adsorption and activation, collaboratively benefiting from the intrinsic unoccupied d orbitals of transition metal components, reformative electronic structure by oxygen vacancies and elevated electron injection possibility into the antibonding orbital of nitrogen molecule via conductive carbon wrapper. Both actual experiments and theoretical investigations attest the catalytic activity improvement mechanism, rendering the C@CoFe2O4-x nanocube design strategy efficient and valid.

Electrochemical CO2 reduction reaction (CO2RR) offers an appealing route to simultaneously store intermittent renewable energy as value-added chemicals and close carbon cycle. Silver (Ag) catalyst is a promising candidate for the electrochemical conversion of CO2 to CO, but the electrocatalytic properties are still insufficient for practical applications. Herein, we put forward a strategy to in situ reconstruct a heterogeneous Ag2S/Ag interface structure, in which their strong interactions facilitate CO2RR performance. The in situ reconstructive Ag2S/Ag catalyst achieves a large current density of 421.7 ± 14.4 mA cm–2 at –0.70 V vs. reversible hydrogen electrode (RHE) and maintains steadily at a current density of 244.5 ± 31.8 mA cm–2 and CO Faradaic efficiency of 99.1 ± 0.8 % at –0.49 V vs. RHE for 50 h, superior to state-of-the-art CO-selective Ag-based catalysts. Density functional theory calculations reveal that the in situ reconstructive Ag2S/Ag interface active sites stabilize the *COOH intermediate during CO2RR process.

Electrochemical reduction of carbon dioxide provides a feasible solution to the energy and climate crisis. Bi-based catalysts are promising candidates to electrochemically convert carbon dioxide (CO2) into formic acid or formate. Herein, ligand-stabilized Bi nanosheets are obtained from in-situ electrochemical reduction of a Bi-based metal-organic framework, which exhibit remarkable electrocatalytic performance for CO2 reduction. A high Faradic efficiency of 98 % for formate is achieved at a potential of -0.80 V vs. reversible hydrogen electrode (RHE) with an improved durability over 40 h. The remarkable electrocatalytic activity and stability could be attributed to the in-situ generated catalyst with abundant under-coordinated Bi active sites, which are effectively stabilized by residual ligands adsorbed on surface. This study demonstrates that ligand-stabilized under-coordinated surface sites would be facilely generated from in-situ transformation of metal-organic precursors for highly efficient CO2 conversion.

Serious surface recombination and sluggish reaction kinetics hamper the photoelectrochemical (PEC) performance from being efficient. Although coupling oxygen evolution catalysts on photoanodes to accelerate electrode reactions has been demonstrated an effective strategy to enhance photocurrent, the surface recombination still limits the performance to an ideal level. Herein, a novel multi-step hole transfer strategy is developed for accelerating hole transport and thus suppressing the surface recombination. In this system, porphyrin and polyaniline both act as hole transfer layers, which construct an effective stair-stepping hole transfer channel to ensure much more holes take part in water oxidation process. This simple interface modulation system exhibits a remarkable photocurrent of 4.5 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode (RHE), AM 1.5 G illumination) accompanied with good stability and provides a promising strategy for the design of efficient photoanodes for solar conversion.

As an artificial leaf, a tandem device for zero-bias solar water splitting is a capable solution for practical hydrogen production. Despite a promise, poor charge transport of BiVO4 hampers photoelectrochemical performances under front-side illumination, which is a hindrance to the tandem system. Herein, we design a new photoanode comprising nanoporous BiVO4 and SnO2 nanorods focused on the charge separation via structural and interfacial engineering. BiVO4/SnO2 photoanode exhibits not only remarkable charge separation efficiency of 97% but also, by loading NiFe as a co-catalyst for water oxidation, high photocurrent density of 5.61 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under front-side 1 sun illumination. Consequently, a tandem cell comprising NiFe/BiVO4/SnO2 photoanode and perovskite/Si tandem solar cell generates an operating photocurrent density of 5.90 mA cm−2 with a solar-to-hydrogen conversion efficiency of 7.3% in zero-bias. This work would be a significant step to develop spontaneous solar hydrogen production.

Herein, we proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N2 absorption and activation by tuning the center positions of pz orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). We theoretically and experimentally investigated the influences of nonmetallic elements of B as electron acceptor, and S and P as electron donor on tuning NRR activity. We revealed that the heteroatom-doping of S atoms induced changing of center position of the pz orbital of B facilitates the adsorption of N2 on S-C-B sites and reduces the energy barriers for rate-determining steps. The S6.23-B8.09/CNFs exhibits the highest NRR activity with high Faradaic efficiency of 22.4 % and NH3 yield of 0.223 μmol h−1 cm-2 at −0.7 V versus reversible hydrogen electrode. The combined computational and experimental works uncover the relationship between the p-band center of heteroatom doped carbon catalysts and NRR activity.

A typical mode of CO2 activation is that d electrons at the d orbital of transition metals transfer to the unoccupied π* orbital of CO2. Thus the exploration of the relationship between d-electron behaviors and CO2 activation is of great importance. Herein, we demonstrate that high-spin state of 3d electrons in Co2+ facilitated the activation of CO2 over Co-salophen-X (X represents to Cl, Br, or I). Among these catalysts, Co-salophen-Br exhibited the highest Faradaic efficiency for CO. Notably, the Faradaic efficiency for CO over Co-salophen-Br reached 98.5 % at −0.70 V versus reversible hydrogen electrode, which was 1.5 and 1.2 times as high as those over Co-salophen-Cl (64.8 %) and Co-salophen-I (81.8 %), respectively. Density functional theory calculations revealed that high-spin state of Co sites decreased the reaction energy barrier for the formation of CO. Based on the analysis of electronic state, the ratio of high-spin state was 65.6 % for Co-salophen-Br, which was the highest among the three Co-based molecules. The Co sites with high-spin state promoted the electron transfer from high-energy 3d orbital (3dz2 and 3dx2-y2) of Co to the unoccupied π* orbital of CO2, improving catalytic performance.

Tuning the geometric and electronic structure of bimetallic electrocatalyst to facilitate a specific reaction pathway and offer more active sites is a promising avenue for enhancing activity and selectivity of electrocatalytic CO2 reduction reaction (eCO2RR). Owing to formation of Bi-Cu interface through the separated growth of Bi and Cu atoms on defective copper foam, the Bi-Cu bimetallic electrode converts CO2 to formate with an allured Faradaic efficiency (94.37%) and partial current density (27.85 mA cm−2) at -0.91 Vversus reversible hydrogen electrode (RHE). Notably, such electrode with tight moss-like structure delivers the excellent durability under 58 h electrolysis, outperforming most of the current Bi-based catalysts. Moreover, we have experimentally shown that KOH is a better electrolyte than KHCO3 due to the lower solution resistance and more confinement of free CO2 gas, and the alkaline anion-exchange membrane is more ideal than the cation-exchange membrane counterpart, owing to the enhancement of formate selectivity by suppressing the evolution of H2. This study inspires a complete set of concepts for highly converting CO2 to formate that contains the design of effective electrocatalysts, the role of growth substrate, the effect of different electrolytes and membranes.

A FeCoW oxy–hydroxide gel coated Fe 2 O 3 film photoanode has been examined for photoelectrochemical (PEC) water oxidation reaction. The FeCoW coating acts as a hole storage layer, resulting in efficient hole extraction from Fe 2 O 3 for water oxidation. In addition, the surface state of FeCoW/Fe 2 O 3 shifts to higher position, thus allows for a lower turn–on voltage ( V on ) of the photocurrent. The composite anode exhibits an 84% increase of the photocurrent, at 1.23 V versus reversible hydrogen electrode (RHE), over the bare Fe 2 O 3 photoanode. The V on is as low as 0.67 V vs. RHE. The applied bias photon–to–current efficiency of the composite is 2.7 times higher than that of the bare Fe 2 O 3 . Moreover, an extremely low bias photoresponse of 0.45 V vs. RHE and a good stability are observed with the FeCoW/Fe 2 O 3 photoanode. Besides, with changing of the thickness of the FeCoW coating slurry, the PEC performance of the FeCoW/Fe 2 O 3 photoanode can be tuned.

A high-performance bismuth vanadate (BiVO 4 ) photoanode cocatalyzed with an ultrathin α-Fe 2 O 3 layer was fabricated for photoelectrochemical water splitting and organic pollutant degradation. The ultrathin α-Fe 2 O 3 layer, which can faciliate the holes transfer to the surface efficiently and thus avoid high charge recombination, was deposited on the surface of the BiVO 4 photoanode using a spin-coating-based successive ionic layer adsorption and reaction (SILAR) method. The Fe 2 O 3 /BiVO 4 photoanode was characterized by various techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, while its photoelectrochemical activity was investigated by linear sweep voltammetry and incident photon-to-current conversion efficiency (IPCE). The optimized Fe 2 O 3 /BiVO 4 photoanode demonstrated a photocurrent density of 1.63 mA cm −2 at 1.23 V vs . a reversible hydrogen electrode (RHE) in a 0.1 M KH 2 PO 4 (pH 7) electrolyte under simulated AM1.5G solar light and an IPCE value above 27% at 400 nm, which were 2.14 times and triple that of pristine BiVO 4 photoanode, respectively. Furthermore, the Fe 2 O 3 /BiVO 4 photoanode showed excellent stability and efficiency for the photoelectrocatalytic degradation of phenol compared with the bare BiVO 4 photoanode. The chemical oxygen demand (COD) removal ratio increased from 42.3% to 68.89% after 120 min, which could be attributed to the efficient separation and transfer of the photogenerated carriers.

Herein, we describe an in-situ hybridization of Nickel Selenide (Ni3Se2) with a Nickel Foam (NF) current collector as an efficient, ultra-durable electrode for the continuous alkaline water electrolysis. Earth abundant, cost effective, non-precious self-made Ni3Se2/NF electrode delivers an oxygen evolution reaction (OER) overpotential value of 315 mV at a current density of 100 mA cm−2 (versus a reversible hydrogen electrode) in aqueous electrolyte of 1 M KOH. On a static current density of 100 mA cm−2, Ni3Se2/NF electrode shows a good OER stability over 285 h with very small potential loss of 5.5% in alkaline electrolyte. Accordingly, the alkaline water electrolyzer constructed with Ni3Se2/NF (anode) and NiCo2S4/NF (cathode), it requires 1.58 V to deliver 10 mA cm−2 current density, with 500 h continuous operation in 1 M KOH. In addition, we demonstrate that the light-driven water splitting using solar panel, it can be a promising approach to facilitate true independence from electricity in H2 fuel economy. Overall, this methodology is one of the appropriate energy efficient ways to reduce the cost of water splitting devices, as it may simplify the diverse process and equipment.

Conventional photoelectrodes have shown dominantly single-signal photoelectrochemical (PEC) performance under reverse-bias, where only photo-generated minority carriers are involved in water splitting reactions. The extraordinary dynamic-mode operation of PEC water splitting is suggested herein, using the heterophasic copper indium selenide (CIS) with coexisting p- and n-type phases. CIS photoelectrodes with an interleaved p-n blended structure generate substantial photocathodic/-anodic currents resulting in transient spikes followed by saturation at negative/positive potential under light illumination. Then, the interleaved inner-depletions function as the charge transport pathway. Pulsed-bias (0 and 0.8 V vs. reversible hydrogen electrode) with a suitable frequency applied to the p-n blended CIS photoelectrodes under steady light illumination results in an extremely high photocurrent density of approximately 25 mA/cm2 (spike) and 10 mA/cm2 (saturation). Furthermore, the pulse-driven PEC operation shows remarkably high hydrogen evolution efficiency by suppressing the formation of large-size cluster bubbles and an intrinsic electric double layer.

M-N-C single-atom electrocatalysts recently have received significant attention because of high catalytic activity and maximal atom utilization. Here, it is firstly reported that macrocycle cucurbit[6]uril (CB[6]) self-assembly was employed as precursor to fabricate M-N-C single-atom electrocatalysts for the Zn-air battery (ZAB). This template-free method using CB[6] self-assembly acquires the holey N-doped matrixes with hierarchical micro/mesoporous structure. The Fe loaded N-doped holey carbon single-atom electrocatalyst (Fe-NHC) exhibited high activity with the half-wave potential (E1/2) of 0.89 V versus reversible hydrogen electrode (RHE) for oxygen reduction reaction (ORR) in alkaline condition, which was better than those of Co or Ni loaded catalyst and commercial Pt/C (E1/2 = 0.83 V). Moreover, the ZAB employing Fe-NHC catalyst achieved higher power and energy density with longer-term stability than those of Pt/C + Ir/C catalyst. This work provided a promising strategy to design stable and highly efficient catalyst for long-life electrochemical storage devices.

MoS2 has been proven to be an efficient NRR electrocatalyst, the activation of inert basal plane and rational utilization of basal plane have become the key to further increasing the activity. The defects of basal plane help to expose active sites, however, they cannot activate basal plane to promote NRR. Herein, based on the calculation results, we designed porous atomic layered 2H-MoS2(PAL-MoS2) by one-step calcination treatment. The porosity of the basal plane effectively utilizes basal plane atoms while the presence of adjacent Mo atom pairs improves the NRR performance. A high Faradic efficiency of 44.36 % and a sizeable NH3 yield of 3405.55 μg h−1 mgcat−1 (1.98 μg h−1 cm−2) at ‒0.1 V vs. reversible hydrogen electrode are obtained in 0.1 M HCl under ambient conditions, as far as we know, outperforming most of Mo-based NRR electrocatalysts reported before. Furthermore, this catalyst also exhibits high selectivity, electrochemical stability and good performance characterization.

To seek effective strategies that improve the photoelectrochemical water oxidation performance of hematite (α-Fe2O3) photoanodes is still challenging owning to their abundant surface states and low charge transfer efficiency. Herein, a facile impregnation method with an annealing process was developed to synthesize MoO3 modified Fe2O3 photoanodes using the MoO3 layer as an effective passivation component to decrease surface states and thus to improve the charge separation and transfer process at the electrode/electrolyte interfaces. The oxygen vacancies were subsequently introduced to steer the electrical conductivity, and further to boost the charge separation and transfer. The optimized MoO3-x/Fe2O3-x photoanode displays a photocurrent density of 2.6 mA cm–2 at 1.23 V versus the reversible hydrogen electrode under AM 1.5 G irradiation, 2.2 times that of the Fe2O3 (1.2 mA cm–2). The synergetic integration of passivation layer and oxygen vacancies on photoelectrodes heralds an efficient paradigm for solar energy conversion.

Electrochemical N2 reduction is developing as an appealing carbon-neutral strategy for NH3 artificial synthesis but seriously influenced by requiring high-efficiency electrocatalysts for the N2 activation at ambient conditions. Here, we reported that defective-rich ZnS nanoparticles supported on reduced graphene oxide (DR ZnS-rGO) acts as a high-efficiency electrocatalyst for ambient N2-to-NH3 conversion with excellent selectivity. In 0.1 M HCl, such DR ZnS-rGO presents a large NH3 yield of 51.2 μg h–1 mgcat.–1 (−0.15 V vs. reversible hydrogen electrode, RHE) and a high faradic efficiency of 28.2 % (−0.10 V vs. RHE), as well as high electrochemical and structure stability. Isotopic labelling samples experiments reveal that the synthetic NH3 directly arise from the supplied N2. Density functional theory calculations demonstrated that the engineering S vacancies in DR ZnS-rGO not only provide reaction sites for N2-to-NH3 conversion but activate of N2 molecules.

Hematite (α-Fe2O3) based nanomaterials are considered as the most promising photoelectrodes for solar water splitting. However, some inherent shortcomings like high density of surface states is still the critically challengeable issue. This paper reports the integration of In2O3 nanolayers (NLs) on the surface of worm-like Fe2O3 films to significantly improve the photoelectrochemical (PEC) water oxidation activity. The In2O3 NLs on the modified α-Fe2O3 photoelectrodes exhibit dual positive effects on PEC performance: i) acting as the passivation material to decrease surface electron-hole recombination losses; ii) constructing heterojunctions with Fe2O3 to facilitate efficient separation of surface charges and spatial transfer with extended lifetimes. The resulting treated Fe2O3 photoanode yields a current density of 3.4 mA cm―2 at 1.23 V vs. reversible hydrogen electrode and high incident photon-to-current efficiency of 80 % at 400 nm. These results may bring inspiration to introduce multifunctional modifiers on photoelectrodes that offer practically high-performance PEC applications.

The sluggish catalytic reactivity on the surface of most semiconductors is a common obstacle in developing photo-electrochemical (PEC) electrodes. Loading cocatalysts becomes a plausible scenario but remains challenging in the integration with semiconductors due to the complicated interfacial issues. This work introduces an feasible strategy of activating surface reactivity, alternative to cocatalysis, in cooperating with semiconductor photoactivity to boost PEC performance. We apply an ionized argon plasma technology on three-dimensional (3D) nanoporous BiVO4 (BVO) to controllably generate surface oxygen vacancies, which enable surface activation favoring charge separation and transfer towards water oxidation reaction (WOR). A remarkable photocurrent density of 4.32 mA cm−2 is achieved at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5 G illumination, which is a record among the reported single BVO photoanodes and even surpasses the performances of most cocatalyst-assisted ones. This study provides an alternative solution to sluggish catalytic kinetics on semiconductor photoelectrodes, thus paving a novel avenue to modulate cooperation with photoactivity in PEC technology.

Ni(OH)2 nanosheet arrays are in situ prepared on Ni foam through very straightforward ultrasonication in HCl solution and the following rinsing and drying procedures. Value-added formate and hydrogen could be co-produced by selective oxidation of methanol without carbon dioxide emissions and water reduction over Ni(OH)2 nanosheet arrays bifunctional electrocatalysts. Energy depletion for hydrogen evolution from water could be reduced by integrating with selective methanol oxidation rather than oxygen evolution. The prepared Ni(OH)2 nanosheet arrays exhibits high activity for selective methanol oxidation in alkaline methanol-water solution. It gives a low potential of only 1.36 V (vs. reversible hydrogen electrode) to drive the current density of 100 mA cm−2. The faradaic efficiencies of formate are approximately 100% with the current densities from 10 mA cm−2 to 100 mA cm−2. Moreover, it is easy to separate the anodic and cathodic products without help of any membrane, which greatly simplifies the electrolysis system.

Electrocatalytic synthesis of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e− ORR) is an ideal method for the on-site H2O2 production. Herein, Ni3B is identified as an active, selective, and stable catalyst for ORR to generate H2O2, which exhibits a high selectivity of over 90 % and an onset potential of ∼0.7 V versus the reversible hydrogen electrode (RHE). Furthermore, the mass activity of Ni3B is about 16.5 A g-1 at 0.52 V (RHE), which is comparable to some noble metal alloys. Our experimental results suggest that the high performance of Ni3B originates from the alloying process of Ni and B atoms. The density functional theory calculations reveal that the inner B atoms with high electronegativity decrease the state density of Ni-3d orbital near the Fermi level relative to Ni, which optimizes the binding energy of OOH* and makes Ni3B a highly efficient and stable catalyst for the two-electron ORR.

Searching for non-noble-metal hydrogen evolution reaction (HER) electrocatalysts with high efficiency and excellent durability is a great challenge for the hydrogen-based energy industry. In this paper, a three-dimensional self-supported hydrogen evolution cathode is present, where the MoP nanosheet array was grown on flexible carbon cloth (MoP NA/CC) via a two-step strategy: hydrothermally growing MoS 2 nanosheet array on CC (MoS 2 NA/CC) in advance, and then phosphidation to chemically convert the MoS 2 NA/CC precusor into MoP NA/CC. When used as an integrated three-dimensional electrode for HER, MoP NA/CC shows a quiet low onset overpotential (50 mV vs reversible hydrogen electrode), high current density (j > 10 mA cm −2 at η = 124 mV), and a small Tafel slope (58 mV dec −1 ), as well as remarkable stability (

The development of inexpensive metal-free catalysts with high activity and stability as substitutes for carbon-supported platinum catalysts (Pt/C) in the oxygen reduction reaction (ORR) remains a great challenge. In this paper, we report a novel type of self-constructed, carbon nanoparticle (CNP)-coated porous biocarbon prepared from a natural, readily available, and renewable plant moss (Weisiopsis anomala) with a single precursor using template-free heat treatment. The CNPs were self-sponsored from the moss, which were simultaneously self-packed on the moss-derived carbon matrix via strong interactions between the hydroxyl and carbonyl functional groups of the CNPs and the moss-derived carbon matrix during the hydrothermal treatment. After being further carbonized at 900 °C, the moss-derived, CNP-coated biocarbon material had a larger surface area than that of the CNP-free, moss-derived biocarbon material. Electrochemical characterization showed that the CNP-coated biocarbon had a high activity in the ORR with an onset potential of 0.935 V vs. the reversible hydrogen electrode (RHE); this value is close to that of a commercial Pt/C catalyst (0.962 V vs. RHE) and is more positive than that of a CNP-free biocarbon material. The CNP-coated biocarbons also displayed a high limited current density, excellent long-term stability and resistance to methanol crossover, offering performance characteristics superior to those of Pt/C. Moreover, a microbial fuel cell (MFC) equipped with a CNP-coated biocarbon cathode outperformed an MFC with a Pt/C cathode in terms of energy output. This study presents a new approach for the production of inexpensive nanostructured carbon materials that exhibit high performance in the ORR from a natural resource.

Herein, we demonstrated a one-step ammonia treatment for fabricating homostructural Ta3N5 nanotube/nanoparticle photoanodes with a top-open structure. Compared with the relatively low activities of traditional Ta3N5 nanotube photoanode, this homo-photoanode exhibited a remarkably enhanced photocurrent density (1.58 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE)). Moreover, after the decoration of Co(OH)x cocatalyst, the photocurrent density could be further increased up to 8.73 mA cm−2 at 1.23 VRHE, accompanying with the significantly improved water oxidation stability as well as an evident negative shift of onset-potential (200 mV). More detailed studies reveal that the significantly promoted PEC activities should be attributed to the matched bandgaps between Ta3N5 nanotube and nanoparticle as well as the ordered top-open nanoarchitecture, which could accelerate charge separation and provide more active sites for water oxidation. Thereby, the construction of homostructural semiconductor photoanodes should be highly promising for promoting the development of PEC water splitting for practical applications.

Highly photoelectrochemical water oxidation efficiency could be realized by means of efficient photogenerated holes transfer pathway and low-cost cocatalysts. Here, we have integrated an ultrathin Al2O3 layer and novel copper-cobalt oxide (CuCoOx) cocatalyst on α-Fe2O3 photoanode to construct unobstructed holes transfer pathway and improve PEC activity. The resultant α-Fe2O3/Al2O3/CuCoOx photoanode exhibits high photocurrent density of 2.23 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (VRHE) and negative onset potential of 0.7 VRHE, which is about 17.6 times higher and 200 mV cathodic shift than bare α-Fe2O3 nanorod arrays. Detailed experimental results indicate the surface recombination passivation function of Al2O3 layer and improvement in charge separation and transfer kinetics of the role of low overpotential of CuCoOx with abundant oxygen vacancies for OER. The comparison discussion with CoOx and CuOx oxygen evolution catalysts (OECs) further illustrates the excellent catalytic performance of the CuCoOx. This work points to the effective utilization of novel but cheap CuCoOx OECs on photoanodes and provides a strategy for designing high activity photoanodes in photoelectrochemical water oxidation.

We report a unique 2D bismuth metal-organic framework (Bi-MOF) that possesses permanent accessible porosity for efficient electrochemical CO2 reduction (ECR) to HCOOH. The 2D open-framework structure with helical Bi-O rods bridged by tritopic carboxylate ligands exhibits a remarkable Faradaic efficiency for HCOOH formation over a broad potential window, reaching 92.2 % at ∼ –0.9 V (vs. reversible hydrogen electrode, RHE) with excellent durability over 30 h. The mass-specific HCOOH partial current density is up to 41.0 mA mgBi−1, exceeding 4 times higher than that of commercial Bi2O3 and Bi sheets at ∼ –1.1 V (vs. RHE). Operando and ex-situ X-ray absorption fine structure spectroscopy revealed a structural feature associated with Bi-MOF to preserve Bi(3+) during and after long-term ECR. Theoretical calculations further showed that the crystallographically channels with abundant Bi active sites in the MOF structure favor the formation of *HCOO while suppressing the side-reaction of hydrogen evolution, thereby leading to the high selectivity for HCOOH.

Nitrogen-doped carbon metal-free materials are widely used in electrochemical reduction of carbon dioxide due to high earth abundance, structural tunability, and excellent catalytic performance. Although specific surface area and nitrogen content are considered as the two most important factors in affecting the electrochemical performance of nitrogen-doped porous carbon catalysts, it does not always mean that the larger they are, the better the catalytic performance is. Tailoring pore structures and maximizing the catalytic effect of a limited number of nitrogen atoms are the keys to the improvement in the electrochemical performance. Herein, we develop a solvent evaporation induced self-assembly method to synthesize a coal-based nitrogen-doped porous carbon as an efficient metal-free electrocatalyst for CO2 electroreduction. Under the effect of pore shrinkage induced by high temperatures, nitrogen atoms derived from dicyandiamide are inserted into the carbon matrix of coal, and confined in the micropores produced by KOH activation. The stable nitrogen atoms restricted in the micropores can efficiently convert CO2 into CO due to the spatial confinement effect. The electrocatalyst shows a negligible onset overpotential (–0.16 V) for CO product, a maximum CO Faradaic efficiency of 95 % and a large CO production rate of 36.1 μmol h–1 cm–2 at a low potential of –0.67 V versus the reversible hydrogen electrode (vs. RHE). Moreover, its current density can remain stable after 10 h of potentiostatic electrolysis. This work not only provides a promising earth-abundant electrocatalyst for CO2 electroreduction, but would open up a new avenue for improving the electrochemical performance by coordinating the pore structures and active components.

Electrocatalytic conversion of methane (CH4) to valuable chemicals under mild conditions is an attractive approach that combines the direct utilization of natural gas as a hydrocarbon feedstock and the chemical storage of renewable electricity. However, it remains a great challenge due to the intrinsic chemical inertness of CH4. Here we report that a NiO/Ni interface constructed by calcination can act as the active site for the electrooxidation of CH4 to alcohols especially ethanol. With the optimized NiO/Ni interface catalyst, an 89 % Faradaic efficiency (FE) for ethanol production with a yield of 25 μmol∙gNiO−1∙h−1 at 1.40 V versus reversible hydrogen electrode (RHE) was achieved. Experiments and density functional theory (DFT) calculations demonstrated that the NiO/Ni interface enables efficient C H activation and C C coupling, leading to the highly selective formation of ethanol from CH4 electrooxidation.

Electrocatalytic nitrogen reduction offers a vital approach for nitrogen fixation in a green and sustainable way, but the low solubility of nitrogen and the competitive hydrogen evolution reaction still impede its further development. Inspired by the structure of gas-trapping hydrophobic hair on a subaquatic spider and the function of hemocyanin in its blood, in the present work, an aerophilic-hydrophilic heterostructured electrode is constructed by using aerophilic ultrathin porous Bi5O7I nanotubes and hydrophilic carbon spheres. Besides, the electrolyte is functionalized with suspended ultrathin porous Bi5O7I nanotubes. The Faradaic efficiency is increased from 5.19 % to 13.42 %, and the ammonia yield is boosted from 7.96 to 31.46 mg h−1m-2 by the new way at -0.4 V versus reversible hydrogen electrode under ambient conditions. Furthermore, the highest yield rate of 85.45 mg h−1 m-2 is achieved with a configured flow cell. This work presents a promising biomimetic strategy to boost electrocatalytic N2 fixation proceed from electrode and electrolyte.