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The electrocatalytic methanol conversion is of importance in direct methanol fuel cell, biomass reforming, and hydrogen generation. To achieve a “carbon-neutral” target, CO2 byproducts derived from biofuels should be mitigated. In contrast to the complete oxidation of methanol to CO2, the selective oxidation of methanol to formate is a CO2-emission-free route without the generation of toxic CO intermediates. Herein, we present a highly active catalyst based on transition-metal disulfide nanosheet arrays supported on Ni foam for methanol conversion. Through composition screening, we find that the FeCoNi disulfide nanosheet exhibits a highly efficient and selective methanol-to-formate conversion. The surface reconstruction of this catalyst allows us to produce 0.66 mmol cm−2 h−1 of formate at low potential (1.40 V) with high faradaic efficiency of > 98%. This work offers a substantial composition tuning strategy to construct noble-metal-free active multi-metal sites for CO2-emission-free conversion of methanol to value-added formate.

Atomically ordered intermetallic nanoparticles are promising for catalytic applications but are difficult to produce because the high-temperature annealing required for atom ordering inevitably accelerates metal sintering that leads to larger crystallites. We prepared platinum intermetallics with an average particle size of5 nanometers on porous sulfur-doped carbon supports, on which the strong interaction between platinum and sulfur suppresses metal sintering up to 1000°C. We synthesized intermetallic libraries of small nanoparticles consisting of 46 combinations of platinum with 16 other metal elements and used them to study the dependence of electrocatalytic oxygen-reduction reaction activity on alloy composition and platinum skin strain. The intermetallic libraries are highly mass efficient in proton-exchange-membrane fuel cells and could achieve high activities of 1.3 to 1.8 amperes per milligram of platinum at 0.9 volts.

Efficient and robust electrocatalysts are required for the oxygen evolution reaction (OER). Photosystem II-inspired synthetic transition metal complexes have shown promising OER activity in water-poor or mild conditions, yet challenges remain in the improvement of current density and performance stability for practical applications in alkaline electrolytes in contrast to solid-state oxide catalysts. Here, we report that a nickel pseudo-complex (bpy)zNiOxHy (bpy = 2,2'-bipyridine) catalyst, which bridges solid oxide and molecular catalysts, exhibits the highest OER activity among nickel-based catalysts with a turnover frequency of 1.1 s-1 at an overpotential of 0.30 volts, even outperforming iron-incorporated nickel (oxy)hydroxide under an identical nickel mass load. Benefiting from the strong coordination between bpy and nickel, this (bpy)zNiOxHy catalyst exhibits long-term stability in highly alkaline media at 1.0 mA cm-2 for over 200 h and at 20 mA cm-2 for over 60 h. Our findings indicate that dynamically coordinating a small amount of bpy in the catalyst layer efficiently sustains highly active nickel sites for water oxidation, demonstrating a general strategy for improving the activity of transition metal sites with active ligands beyond the incorporation of metal cations to form double-layered hydroxides.

Electrochemical N2 reduction provides a green and sustainable alternative to the Haber-Bosch technology for NH3 synthesis. However, the extreme inertness of N2 molecules is a formidable challenge, which requires the development of an active electrocatalyst to drive the N2 reduction reaction (NRR) for NH3 production at ambient conditions. Herein, we demonstrate the development of La-doped TiO2 nanorods as an efficient NRR electrocatalyst for ambient NH3 synthesis. The optimized La-TiO2 catalyst offers a large NH3 yield of 23.06 μg h−1 mgcat−1 and a high Faradaic efficiency of 14.54% at –0.70 V versus reversible hydrogen electrode in 0.1 M LiClO4, outperforming most La- and Ti-based catalysts reported before. Significantly, it also demonstrates high electrochemical stability and its activity decay is negligible after 48 h test. The mechanism is further revealed by density functional theory calculations.

This study examines three family therapy cases of adolescents bullying victims in South Korea. We explored factors related to the onset of bullying victimization, family factors, intervention, and ...

Depressing the competitive hydrogen evolution reaction (HER) to promote current efficiency toward carbon-based chemicals in the electrocatalytic CO2 reduction reaction (CO2RR) is desirable. A strategy is to apply the hydrophobically molecular-modified electrodes. However, the molecular-scale catalytic process remains poorly understood. Using alkanethiol-modified hydrophobic Cu as an electrode and CO2-saturated KHCO3 as an electrolyte, we reveal that H2O, rather than HCO3-, is the major H+ source for the HER, determined by differential electrochemical mass spectrometry with isotopic labeling. As a result, using in situ Raman, we find that the hydrophobic molecules screen the cathodic electric field effect on the reorientation of interfacial H2O to a "H-down" configuration toward Cu surfaces that corresponds to the decreased content of H-bonding-free water, leading to unfavorable H2O dissociation and thus decreased H+ source for the HER. Further, density functional theory calculations suggest that the absorbed alkanethiol molecules alter the electronic structure of Cu sites, thus decreasing the formation energy barrier of CO2RR intermediates, which consequently increases the CO2RR selectivity. This work provides a molecular-level understanding of improved CO2RR on hydrophobically molecule-modified catalysts and presents general references for catalytic systems having H2O-involved competitive HER.

Perovskite oxide is a promising alternative to noble metal electrocatalysts for the oxygen evolution reaction (OER). However, as one of the most active oxide catalysts, cubic SrCoO3 presents poor OER performance relative to the theoretically predicted activity. Appropriate introduction of a guest component in the lattice and surface could largely promote the OER activity. Herein, we present a thermal-induced phase-segregation strategy to synthesize a heterostructured SrCo0.8Fe0.5-xO3-δ/FexOy (SC8F5) catalyst for OER. This novel perovskite/Fe3O4 heterostructure allows us to enhance the electrical conductivity ability, increase the Co oxidation state, and activate the surface oxygen to active oxygen species (O22-/O-) for efficient OER. In contrast to the poor stability of SrCo0.8Fe0.2O3-δ, we found that the SC8F5 heterostructure with segregated Fe3O4 on the surface can mitigate surface reconstruction and stabilize the catalyst structure, thereby increasing catalytic stability.

The iron-based catalysts are promising for the oxygen evolution reaction (OER) in alkaline media, yet the inherent dissolution of high-valent iron species induced performance decay during electroca...

We report a regenerable and redox-inactive ZnOxHy layer that was in situ deposited onto metal oxides MOz (M = Co, Fe, and Ni) in alkaline media containing [Zn(OH)4]2− species during water oxidation. An interface dipole was developed at the MOz/Zn interface, resulting in a decrease of the OER overpotential. Exemplified by the CoOz/ZnOxHy bilayer structure, it presented a 155 mV lower overpotential to deliver 10 mA cm−2 and long-term stability relative to the unmodified CoOz film.

Although much is known about the increased rate of a catalyst required for the oxygen evolution reaction (OER), the hole accumulation behaviors of the catalyst on both photo- and dark electrodes re...

Transition-metal (oxy)hydroxides with an abundance of redox metal sites are important for the development of electrochromic devices, rechargeable metal–air batteries, pseudo-capacitors, and industr...

Ni/CoOx sites were supported on an around 2 nm-TiOx modified hematite photoanode for water oxidation. TiOx demonstrates insignificant hole accumulation and a catalytically inactive surface that serves as an ideal platform. We reveal that the NiOx favors the extraction of holes from the TiOx surface, which are efficiently transferred to active CoOx for water oxidation.

Most transition-metal-based oxygen-evolving catalyst surfaces typically experience irreversible compositional and structural variations during oxygen evolution reaction (OER) in hydrolytic and corr...

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Depressing the competitive hydrogen evolution reaction (HER) to promote current efficiency toward carbon-based chemicals in the electrocatalytic CO

We report a regenerable and redox-inactive ZnO

Perovskite oxide is a promising alternative to noble metal electrocatalysts for the oxygen evolution reaction (OER). However, as one of the most active oxide catalysts, cubic SrCoO

2,5-dimethyfuran (DMF), which is produced from 5-hydroxymethyfurfural (HMF) by hydrodeoxygenation (HDO), is a high quality fuel due to the high heating value, the high octane number and the suitable boiling point. Selective hydrogenation of HMF into liquid fuel DMF has been widely researched. In this paper, Co3O4 catalyst was prepared by co-precipitation and was reduced at different temperatures to form Co–CoOx catalysts. The characterization of catalysts was tested by XRD, TEM, XPS, TPR, BET and NH3-TPD. Co–CoOx possessed a high amount of Co metal and CoOx acidic sites, wherein Co worked as the active hydrogenation sites and CoOx acted as the acid promoter to facilitate the selective HDO of HMF to DMF. The synergistic effect of Co–CoOx is the key for HDO of HMF, obtaining 83.3% of DMF yield at 170 °C, 12 h and the reduction temperature of 400 °C. This method not only saves the catalyst cost, but also promotes the utilization of biomass energy.

The fermentation of biomass allows for the generation of major renewable ethanol biofuel that has high energy density favorable for direct alcohol fuel cells in alkaline media. However, selective conversion of ethanol to either CO

The electro-oxidation of methanol to formate is an interesting example of the potential use of renewable energies to add value to a biosourced chemical commodity. Additionally, methanol electro-oxidation can replace the sluggish oxygen evolution reaction when coupled to hydrogen evolution or to the electroreduction of other biomass-derived intermediates. But the cost-effective realization of these reaction schemes requires the development of efficient and low-cost electrocatalysts. Here, a noble metal-free catalyst, Ni1−xFexSe2 nanorods, with a high potential for an efficient and selective methanol conversion to formate is demonstrated. At its optimum composition, Ni0.75Fe0.25Se2, this diselenide is able to produce 0.47 mmol cm−2 h−1 of formate at 50 mA cm−2 with a Faradaic conversion efficiency of 99%. Additionally, this noble-metal-free catalyst is able to continuously work for over 50 000 s with a minimal loss of efficiency, delivering initial current densities above 50 mA cm−2 and 2.2 A mg−1 in a 1.0 m KOH electrolyte with 1.0 m methanol at 1.5 V versus reversible hydrogen electrode. This work demonstrates the highly efficient and selective methanol-to-formate conversion on Ni-based noble-metal-free catalysts, and more importantly it shows a very promising example to exploit the electrocatalytic conversion of biomass-derived chemicals., J.L. obtained International Postdoctoral Exchange Fellowship Program (Talent-Introduction program No. YJ20190126) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. This work was supported from the UESTC start-up funding, the Recruitment Program of Thousand Youth Talents, and the Natural Science Foundation of China (22072013). It was also supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project SEHTOP (ENE2016-77798-C4-3-R) and VALPEC (ENE2017-85087-C3). C.X., Y.Z., and T.Z. are grateful for the China Scholarship Council (CSC) for scholarship support. T.Z., and J.A. acknowledge funding from Generalitat de Catalunya 2017 SGR 327. ICN2 acknowledges support from the Severo Ochoa Programme (MINECO, Grant no. SEV-2013-0295). T.Z. has received funding from the CSC-UAB PhD scholarship program. M.C.S. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 754510 (PROBIST) and the Severo Ochoa programme. IREC and ICN2 are funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program.

Ni/CoOx sites were supported on an around 2 nm-TiOx modified hematite photoanode for water oxidation. TiOx demonstrates insignificant hole accumulation and a catalytically inactive surface that serves as an ideal platform. We reveal that the NiOx favors the extraction of holes from the TiOx surface, which are efficiently transferred to active CoOx for water oxidation.

Crystal α-zirconium phosphate (α-ZrP) was prepared by a hydrothermal method and exfoliated into a layered structure by n-hexylamine (C6H13NH2). Ni-based catalyst (Ni/ZrP) was promoted by loading nickel on the layered α-ZrP via ion exchange. The catalyst was performed to catalyze hydrodeoxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF), and a 68.1% yield of DMF and 100% conversion of HMF were achieved at 240 °C, 5 MPa H2, and 20 h. The DMF yield can still retain 52.8% after five cycles. The characteristics of the catalyst were investigated via N2 adsorption–desorption, X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, pyridine-adsorbed Fourier transform infrared (FTIR) spectra, FTIR spectra, inductively coupled plasma mass spectrometry, and thermogravimetric analysis–mass spectrometry, as well as Raman spectroscopy. A pathway from HMF to DMF was found with MF as the intermediate product, and DMF production was preferable via the −CH2OH group hydrogenolysis of HMF over Lewis acidic sites of Ni/ZrP, which is caused by the zirconium vacant orbits.

The CO2 phase change absorbent, CPCA, as a novel alternative absorbent, has attracted great attention recently. In this work, the CPCAs composed of MDEA/C4–C6 alcohol/H2O were developed by means of the cosolvent effect. The cosolvent effect of MDEA on the solubility of C4–C6 alcohols in H2O was verified. The CPCAs composed of MDEA/1-butanol/H2O were further examined including the species distributions, absorption rate, cycling capacity and regenerability. The initial absorption rates of all CPCAs were higher than that of 30% MDEA, and its maximum value was 2.5 times higher. A different behavior was shown for the CPCAs that an increase in the absorption rate was observed for a period of time when the CPCAs became turbid. The optimal CO2 cycling capacity of CPCA was 2.48 mol CO2 kg−1, which was 70% higher compared to 30 wt% MDEA.

We present a voltammetric, spectroscopic, and atomic-scale microscopic study of how initial interfacial contact with high- and low-pH electrolytes affects the surface voltammetry, near-surface composition, CO binding, and electrocatalytic oxygen reduction reaction (ORR) of dealloyed Pt–Ni alloy nanoparticles deployed in fuel cells. The first contact of the catalyst with the electrolyte is critical for the evolution of the catalytically active surface structure, yet still insufficiently understood. Counter to chemical intuition, we find that voltammetric activation protocols in both pH 1 and pH 13 electrolytes result in similarly Ni-depleted surfaces with similar near-surface Ni/Pt ratios to a 2.5 nm depth, yet vastly different ORR reactivities. On the basis of our combined voltammetric, scanning transmission electron microscopy with the spectroscopic mapping by energy dispersive X-ray (STEM-EDX) microscopic and X-ray photoelectron spectroscopy (XPS) analysis, we conclude that oxygen-saturated alkaline ele...

Co-based nanomaterials have been intensively explored as promising noble metal free oxygen evolution reaction (OER) electrocatalysts. Herein, we first report phase selective synthesis of novel hierarchical CoTe2 and CoTe nanofleeces for efficient OER catalyst. The CoTe2 nanofleeces exhibited excellent electrocatalytic activity and stablity for OER in alkaline media. It has been discovered that the CoTe2 catalyst exhibited superior OER activity to the CoTe catalyst and comparable to the state-of-the-art RuO2 catalyst. Density functional theory calculations showed that the binding strength and lateral interaction of the reaction intermediates on CoTe2 and CoTe are essential for the order of their overpotential and the trend variation at different condition. This study provides value insights for rational design of noble metal free OER catalysts with high performance and low cost by use of Co-based chalcogenides.

By using the salting-out phenomenon to induce phase separation, the novel CO 2 phase change absorbents (CPCAs) composed of MEA/water-miscible alcohol/H 2 O were developed. The absorbents using 1-propanol, 2-propanol and tertiary butanol as the diluent were selected as CPCAs. The CPCAs composed of MEA/1-propanol/H 2 O were further examined include the species distributions in the two phases, physical properties, cyclic capacity and absorbent regenerability. In comparison to 30 wt% MEA/H 2 O, the optimal CO 2 cycle capacity of CPCA is 2.59 mol CO 2 /kg which increase 62% and the volume of CPCA sent to the stripper decreased over 67%. The developed CPCAs would benefit to reduce energy consumption of CO 2 capture.

Due to the high energy consumption in CO2 capture by amine absorbents, CO2 phase change absorbent, CPCA, has attracted a great attention in research institutes recently. Two phases are formed after CO2 absorption with CPCA as the absorbent, and only the CO2-rich phase goes to the stripper, which could potentially reduce the energy consumption. In this work, the CPCAs composed of MEA/1-propanol/H2O were developed based on the principles of aqueous two-phase systems. The effects of temperature, amine concentration, and total CO2 loading on the phase separation of CPCAs were studied. CO2 loading and 1-propanol distributions in two phases under different experimental conditions were measured. The results indicated that the total CO2 loading is the key factor affecting the distribution of components in two phases. Moreover, in comparison to traditional 30 wt % MEA, the initial absorption rates of all CPCAs were higher than that of MEA, and its maximum value was 5 times higher. The cyclic capacity of the CPCA w...

Heterointerface tailoring is of importance for the catalytic activity enhancement of nanomaterials in various reactions owing to the charge polarization at the interface. We report an accurate manipulation of a replacement reaction for Pt/PtTe heteronanowire and PtTe homonanowire fabrication. Their geometric structures are controlled by using the aged K2PtCl4 in ethylene glycol (EG) as Pt precursors with self-tuned coordination state and structure. The aging process enables the slow conversion of PtCl42– to linear structured PtmCln leading to their tunable oxidation ability. The Pt–Pt bond formation during aging has been revealed by time-resolved in situ UV–vis and X-ray absorption fine structure (XAFS) spectroscopies. The coexistence of a highly active Te template, PtCl42– ions, and linear structured PtmCln complexes allows Pt nanoparticles (NPs) to grow in situ on the PtTe nanowires (NWs), forming a controllable interface structure that served as catalytic active sites and charge transfer location. In c...

The development of economic water oxidation catalysts is a key step toward large-scale water splitting. However, their current exploration remains empirical to a large extent. Elucidating the correlations between electronic properties and catalytic activity is crucial for deriving general and straightforward catalyst design principles. Herein, strongly correlated electronic systems with abundant and easily tunable electronic properties, namely La(1-x)Sr(x)BO3 perovskites and La(2-x)Sr(x)BO4 layered perovskites (B = Fe, Co, Ni, or Mn), were employed as model systems to identify favorable electronic structures for water oxidation. We established a direct correlation between the enhancement of catalytic activity and the insulator to metal transition through tuning the electronic properties of the target perovskite families via the La(3+)/Sr(2+) ratio. Their improved photochemical water oxidation performance was clearly linked to the increasingly metallic character. These electronic structure-activity relations provide a promising guideline for constructing efficient water oxidation catalysts.

We performed in situ transmission electron microscopy of phase-segregated octahedral Pt–Ni alloy fuel cell nanocatalysts under thermal annealing to study their morphological stability and surface compositional evolution. The pristine octahedral Pt–Ni nanoparticles (NPs) showed Pt-rich corners/edges and slightly concave Ni-rich {111} facets. Time-resolved image series unequivocally revealed that upon annealing up to 500 °C, the Pt-rich surface atoms at the corners/edges diffused onto and subsequently covered the concave Ni-rich {111} surfaces, leading to perfectly flat Pt-rich {111} surfaces with Ni-rich subsurface layers. This was further corroborated by in situ aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy. Our results propose a feasible approach to construct shaped Pt alloy nanoparticles with Pt-rich {111} surfaces and Ni-rich subsurface layers that are expected to be catalytically active and stable for the oxygen reduction reaction, thus providing ...

The chemical and morphological stability of size- and shape-selected octahedral PtNi nanoparticles (NP) were investigated after different annealing treatments up to a maximum temperature of 700 °C in a vacuum and under 1 bar of CO. Atomic force microscopy was used to examine the mobility of the NPs and their stability against coarsening, and X-ray photoelectron spectroscopy to study the surface composition, chemical state of Pt and Ni in the NPs, and thermally and CO-induced atomic segregation trends. Exposing the samples to 1 bar of CO at room temperature before annealing in a vacuum was found to be effective at enhancing the stability of the NPs against coarsening. In contrast, significant coarsening was observed when the sample was annealed in 1 bar of CO, most likely as a result of Ni(CO)4 formation and their enhanced mobility on the support surface. Sample exposure to CO at room temperature prior to annealing led to the segregation of Pt to the NP surface. Nevertheless, oxidic PtOx and NiOx species still remained at the NP surface, and, irrespective of the initial sample pretreatment, Ni surface segregation was observed upon annealing in a vacuum at moderate temperature (T < 300 °C). Interestingly, a distinct atomic segregation trend was detected between 300 and 500 °C for the sample pre-exposed to CO; namely, Ni surface segregation was partially hindered. This might be attributed to the higher bonding energy of CO to Pt as compared to Ni. Annealing in the presence of 1 bar CO also resulted in the initial surface segregation of Ni (T < 400 °C) as long as PtOx and NiOx species were available on the surface as a result of the higher affinity of Ni for oxygen. Above 500 °C, and regardless of the sample pretreatment, the diffusion of Pt atoms to the NP surface and the formation of a Ni-Pt alloy are observed.

Cocatalysts are usually deposited on semiconductors to accelerate charge transfer/separation and passivate their surface states. Although various methods have been developed to decorate cocatalysts on semiconductors, in situ depositing a transition metal oxide/oxyhydroxide catalyst in alkaline electrolyte remains a challenge. Herein, we present a facile in situ photo-assisted electrodeposition of ultrathin amorphous CoOxHy layer on hematite for efficient solar-driven water oxidation. Compared to Co(II) hydroxide, Co(III) hydroxide is much less soluble in alkaline electrolytes, thus being favorable for deposition above the anodic onset potential of Co(II)/(III). By using this metal valence dependent deposition-dissolution equilibrium, we prepared this highly efficient and adaptive CoOxHy layer on hematite for OER in 1.0 M NaOH containing 1.0 μM Co(II). This method is promising for loading cocatalysts on semiconductors for solar-driven water splitting and is general for developing in situ (photo)electrochemical deposition of nanoscale catalysts.