Developing a large-scale method to produce platinum (Pt)-based electrocatalysts for the oxygen reduction reaction (ORR) is highly desirable to propel the commercialization of the membrane electrode ...assembly (MEA). Here, we successfully report the large-scale production of surfactant-free ruthenium-doped Pt–cobalt octahedra grown on carbon (Ru–Pt3Co/C), which display a much higher ORR activity and stability and MEA stability than Pt3Co/C and Pt/C. Significantly, the in-situ X-ray absorption fine structure result reveals that Ru can drive the reduced Pt atoms to reverse to their initial state after the ORR by transferring a redundant electron from Pt to Ru, preventing the over-reduction of Pt active sites and boosting the chemical stability. Theory investigations further confirm that the doped Ru can accelerate the breach and desorption of oxygen intermediates, making it active and durable for the ORR. The present work sheds light on the exploration of a large-scale strategy for producing advanced Pt-based nanocatalysts, which may offer significant advantages for practical fuel cell applications in the future.
Abstract
Designing efficient catalyst for the oxygen evolution reaction (OER) is of importance for energy conversion devices. The anionic redox allows formation of O-O bonds and offers higher OER ...activity than the conventional metal sites. Here, we successfully prepare LiNiO
2
with a dominant 3
d
8
L
configuration (
L
is a hole at O 2
p
) under high oxygen pressure, and achieve a double ligand holes 3
d
8
L
2
under OER since one electron removal occurs at O 2
p
orbitals for Ni
III
oxides. LiNiO
2
exhibits super-efficient OER activity among LiMO
2
,
R
MO
3
(M = transition metal,
R
= rare earth) and other unary 3d catalysts. Multiple in situ/operando spectroscopies reveal Ni
III
→Ni
IV
transition together with Li-removal during OER. Our theory indicates that Ni
IV
(3
d
8
L
2
) leads to direct O-O coupling between lattice oxygen and *O intermediates accelerating the OER activity. These findings highlight a new way to design the lattice oxygen redox with enough ligand holes created in OER process.
Identifying real active sites and understanding the mechanism of oxygen evolution reaction (OER) are still a big challenge today for developing efficient electrochemical catalysts in renewable energy ...technologies. Here, using a combined in situ/operando experiments and theory, the catalytic mechanism of the ordered OER active Co and Ir ions in Sr2CoIrO6−δ is studied, which exhibits an unprecedented low overpotential 210 mV to achieve 10 mA cm–2, ranking the highest performance among perovskite‐based solid‐state catalysts. Operando X‐ray absorption spectroscopies as a function of applied voltage indicates that Ir4+ ion is gradually converted into extremely high‐valence Ir5+/6+, while the part of Co3+ ion is transferred into Co4+ under OER process. Density functional theory calculations explicitly reveal the order Co‐O‐Ir network as an origin of ultrahigh OER activity. The work opens a promising path to overcome the sluggish kinetics of OER bottleneck for water splitting via proper arrangements of the multi‐active sites in catalyst.
Operando experimental observation of a gradual oxidation state transition from Ir4+ to Ir5+ and further to Ir6+ and theoretical simulation expatiates the origin of ultrafast electrocatalytic water oxidation of the Sr2CoIrO6−δ catalyst with Co‐O‐Ir ordered arrangement.
The electrochemical nitrogen (N2) reduction reaction (N2RR) under mild conditions is a promising and environmentally friendly alternative to the traditional Haber‐Bosch process with high energy ...consumption and greenhouse emission for the synthesis of ammonia (NH3), but high‐yielding production is rendered challenging by the strong nonpolar N≡N bond in N2 molecules, which hinders their dissociation or activation. In this study, disordered Au nanoclusters anchored on two‐dimensional ultrathin Ti3C2Tx MXene nanosheets are explored as highly active and selective electrocatalysts for efficient N2‐to‐NH3 conversion, exhibiting exceptional activity with an NH3 yield rate of 88.3±1.7 μg h−1 mgcat.−1 and a faradaic efficiency of 9.3±0.4 %. A combination of in situ near‐ambient pressure X‐ray photoelectron spectroscopy and operando X‐ray absorption fine structure spectroscopy is employed to unveil the uniqueness of this catalyst for N2RR. The disordered structure is found to serve as the active site for N2 chemisorption and activation during the N2RR process.
Order from disorder: Au nanoclusters with disordered Au atoms anchored on two‐dimensional ultrathin Ti3C2Tx MXene nanosheets are synthesized and prove to be a highly efficient catalyst for the electrochemical synthesis of ammonia. In situ near‐ambient pressure X‐ray photoelectron spectroscopy and operando XAFS spectroscopy are used to investigate the catalyst.
The new TPS 44A beamline at the Taiwan Photon Source, located at the National Synchrotron Radiation Research Center, is presented. This beamline is equipped with a new quick‐scanning monochromator ...(Q‐Mono), which can provide both conventional step‐by‐step scans (s‐scans) and on‐the‐fly scans (q‐scans) for X‐ray absorption fine‐structure (XAFS) spectroscopy experiments, including X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine‐structure (EXAFS) spectral measurements. Ti and Te K‐edge XAFS spectra were used to demonstrate the capability of collecting spectra at the limits of the working energy range. The Ni and Cu K‐edge XAFS spectra for a Cu‐doped Pt/Ni nanocomposite were acquired to test the performance of the newly commissioned beamline. Pt L3‐ and Ru K‐edge quick‐scanning XAFS (QXAFS) spectra for standard Pt and Ru foils, respectively, revealed the stability of the q‐scan technique. The results also demonstrated the beamline's ability to collect XAFS spectra on a sub‐second timescale. Furthermore, a Zn(s)|Zn2+(aq)|Cu(s) system was tested to indicate that the states of the Zn electrode could be observed in real time for charging and discharging conditions using an in situ/operando setup combined with QXAFS measurements.
The new TPS 44A beamline at the Taiwan Photon Source is presented. The beamline is equipped with a new quick‐scanning monochromator (Q‐Mono), which can provide both conventional step‐by‐step scans and on‐the‐fly scans for XAFS spectroscopy experiments, including XANES and EXAFS spectral measurements.
Electrocatalytic water splitting, as one of the most promising methods to store renewable energy generated by intermittent sources, such as solar and wind energy, has attracted tremendous attention ...in recent years. Developing efficient, robust, and green catalysts for the hydrogen and oxygen evolution reactions (HER and OER) is of great interest. This study concerns a facile and green approach for producing RuNi/RuNi oxide nanoheterostructures by controllable partial oxidation of RuNi nanoalloy, which is characterized and confirmed by various techniques, including high‐resolution transmission electron microscopy and synchrotron‐based X‐ray absorption spectroscopy. This nanoheterostructure demonstrates outstanding bifunctional activities for catalyzing the HER and OER with overpotentials that are both among the lowest reported values. In a practical alkali–water‐splitting electrolyzer, it also achieves a record‐low cell voltage of 1.42 V at 10 mA cm−2, which is significantly superior to the commercial RuO2//Pt/C couple and other reported bifunctional water‐splitting electrocatalysts. Density functional theory calculations are employed to elaborate the effect of Ni incorporation. This simple catalyst preparation approach is expected to be transferrable to other electrocatalytic reactions.
RuNi rules: RuNi/RuNi oxide nanoheterostructures have been prepared as a bifunctional electrocatalyst for both the hydrogen evolution and oxygen evolution reactions in alkaline electrolyte, showing a record‐low cell voltage of 1.42 V at 10 mA cm−2 current for overall water splitting.
Nanosized zerovalent iron (NZVI) Fe@Fe 3 O 4 with a core–shell structure derived from photocatalytic MeOH aqueous solution of dinitrosyl iron complex (DNIC) (N3MDA)Fe(NO)2 (N3MDA = ...N,N-dimethyl-2-(((1-methyl-1H-imidazole-2-yl)methylene)amino)ethane-1-amine) (1-N 3 MDA), eosin Y, and triethylamine (TEA) is demonstrated. The NZVI Fe@Fe 3 O 4 core shows a high percentage of zerovalent iron (Fe0 %) and is stabilized by a hydrophobic organic support formed through the photodegradation of eosin Y hybridized with the N3MDA ligand. In addition to its well-known reductive properties in wastewater treatment and groundwater remediation, NZVI demonstrates the ability to form heterostructures when it interacts with metal ions. In this research, Co2+ is employed as a model contaminant and reacted with NZVI Fe@Fe 3 O 4 to result in the formation of a distinct Fe–Co heterostructure, cracked NZVI (CNZVI). The slight difference in the standard redox potentials between Fe2+ and Co2+, the magnetic properties of Co2+, and the absence of surface hydroxides of Fe@Fe 3 O 4 enable NZVI to mildly reduce Co2+ and facilitate Co2+ penetration into the iron core. Taking advantage of the well-dispersed nature of CNZVI on an organic support, the reduction in particle size due to Co2+ penetration, and Fe–Co synergism, CNZVI is employed as a catalyst in the alkaline oxygen evolution reaction (OER). Remarkably, CNZVI exhibits a highly efficient OER performance, surpassing the benchmark IrO2 catalyst. These findings show the potential of using NZVI as a template for synthesizing highly efficient OER catalysts. Moreover, the study demonstrates the possibility of repurposing waste materials from water treatment as valuable resources for catalytic energy conversion, particularly in water oxidation processes.
Protonic ceramic fuel cells (PCFCs), as an efficient energy storage and conversion device, have great potential to solve the serious problems of energy shortage and environmental pollution. Improving ...the proton conductivity of the promising cathode materials is an effective solution to promote the widespread application of PCFCs at low temperatures (450–650 °C). Herein, considering the high oxygen reduction reaction (ORR) activity of BaCoO3-based perovskite oxide and beneficial proton uptake capacity of Zn-doping, we construct BaCo0.4Fe0.4Zn0.1Y0.1O3‑δ (BCFZnY) as the PCFCs cathode, and compare it with the classic triple-conducting cathode BaCo0.4Fe0.4Zr0.1Y0.1O3‑δ (BCFZrY). Different from the general strategy of increasing the initial oxygen vacancy concentration of cathode materials, this work unveils that enhancing the hydration of perovskite oxide with low oxygen vacancy concentration is a more effective strategy to accelerate the proton diffusion in the electrode. Therefore, the BCFZnY cathode achieved excellent proton conductivities of 8.05 × 10–3 and 6.38 × 10–3 S cm–1 as obtained by hydrogen permeation measurements and peak power densities of 982 and 320 mW cm–2 in a BaZr0.1Ce0.7Y0.1Yb0.1O3‑δ-based anode-supported fuel cell at 600 and 450 °C, respectively.
Designing platinum (Pt)-based formic acid oxidation reaction (FAOR) catalysts with high performance and high selectivity of direct dehydrogenation pathway for direct formic acid fuel cell (DFAFC) is ...desirable yet challenging. Herein, we report a new class of surface-uneven PtPbBi/PtBi core/shell nanoplates (PtPbBi/PtBi NPs) as the highly active and selective FAOR catalysts, even in the complicated membrane electrode assembly (MEA) medium. They can achieve unprecedented specific and mass activities of 25.1 mA cm–2 and 7.4 A mgPt –1 for FAOR, 156 and 62 times higher than those of commercial Pt/C, respectively, which is the highest for a FAOR catalyst by far. Simultaneously, they show highly weak adsorption of CO and high dehydrogenation pathway selectivity in the FAOR test. More importantly, the PtPbBi/PtBi NPs can reach the power density of 161.5 mW cm–2, along with a stable discharge performance (45.8% decay of power density at 0.4 V for 10 h), demonstrating great potential in a single DFAFC device. The in situ Fourier transform infrared spectroscopy (FTIR) and X-ray absorption spectroscopy (XAS) results collectively reveal a local electron interaction between PtPbBi and PtBi. In addition, the high-tolerance PtBi shell can effectively inhibit the production/adsorption of CO, resulting in the complete presence of the dehydrogenation pathway for FAOR. This work demonstrates an efficient Pt-based FAOR catalyst with 100% direct reaction selectivity, which is of great significance for driving the commercialization of DFAFC.
Anion exchange membrane fuel cells are limited by the slow kinetics of alkaline hydrogen oxidation reaction (HOR). Here, we establish HOR catalytic activities of single-atom and diatomic sites as a ...function of *H and *OH binding energies to screen the optimal active sites for the HOR. As a result, the Ru-Ni diatomic one is identified as the best active center. Guided by the theoretical finding, we subsequently synthesize a catalyst with Ru-Ni diatomic sites supported on N-doped porous carbon, which exhibits excellent catalytic activity, CO tolerance, and stability for alkaline HOR and is also superior to single-site counterparts. In situ scanning electrochemical microscopy study validates the HOR activity resulting from the Ru-Ni diatomic sites. Furthermore, in situ x-ray absorption spectroscopy and computational studies unveil a synergistic interaction between Ru and Ni to promote the molecular H
dissociation and strengthen OH adsorption at the diatomic sites, and thus enhance the kinetics of HOR.
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