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Abstract Ultra small nano-sized cobalt catalysts supported on MCM41 have been prepared via simple one-pot synthesis procedure, the microstructure of as-prepared catalysts was characterized by XRD, N 2 adsorption-desorption, SEM, TEM and ICP-AES. The results indicated that the Co/MCM41 catalysts possessed well-ordered mesoporous morphology, and the cobalt loading had negligible influence on MCM41 support. Catalytic hydrogen production experiments demonstrated that the catalyst with the cobalt loading of 0.5 wt% (Co/MCM41–0.5w) exhibited the highest catalytic activity over all investigated catalysts, its turn-over frequency is higher than that of Ru/C catalyst and comparable to that of Co-P/Ni foam catalyst. Graphical abstract Unlabelled Image Highlights • Nano-sized cobalt particles catalysts supported on MCM41 (Co/MCM41). • Well-ordered porous morphology. • A simple one-pot synthesis procedure. • High catalytic activity for alkaline borohydride hydrolysis reaction. [ABSTRACT FROM AUTHOR]

Development of highly active, low cost, ecologically friendly, and durable homogenous catalysts for hydrogen generation from hydrolysis of borohydride is one of the most desirable pathways for future hydrogen utilization. The unexpected catalytic activities of inorganic ammonium species and the corresponding mechanisms underpinning them are studied. The catalytic activities of the ammonium species are higher than or comparable to those of mostly investigated noble-metal/transition-metal catalysts (such as Pd, Pt, Ni, and Co) but are considerably cheaper, more environmentally friendly, and more readily available. Quantum chemical calculations indicate that the unique ammonium-induced reaction pathway involved with a barrierless elementary reaction at the reaction entrance and the formation of the highly active intermediate BH3 are responsible for the unexpected catalytic activities and the significantly accelerated hydrogen generation. [ABSTRACT FROM AUTHOR]

[Display omitted] Developing a high-activity and low-cost catalyst to reduce the anodic overpotential is essential for hydrogen production from water splitting. In this work, a hetero-structured Co 7 Fe 3 /Mo 2 C@C catalyst has been developed to efficiently catalyze oxygen evolution reaction (OER), the overpotential (ƞ 10) of Co 7 Fe 3 /Mo 2 C@C-catalyzed OER with current density of 10 mA/cm2 is about 254 mV, substantially lower than the counterparts of Co 7 Fe 3 @C-catalyzed OER (ƞ 10 , 308 mV) and Mo 2 C@C-catalyzed OER (ƞ 10 , 439 mV), close to that of OER catalyzed by commercial RuO 2. The mechanistic studies reveal that the distinct electron transfer across the Co 7 Fe 3 /Mo 2 C interface results in electron-deficient Co 7 Fe 3 , which has been identified as the highly active catalytic sites. Density functional theory (DFT) calculations manifest that Mo 2 C induces a distinct decrease in electron density on Co 7 Fe 3 and upgrades the d -band centers of Co and Fe in Co 7 Fe 3 towards Fermi energy level, thus substantially lowering the energy barrier of the rate-determining reaction step and conferring significantly improved OER activity on the Co 7 Fe 3 /Mo 2 C@C catalyst. [ABSTRACT FROM AUTHOR]

Tuning the metal-support interaction is a general strategy of regulating the chemical state of catalytic active site for high-efficiency hydrogen production from ethanol steam reforming (ESR) reaction. In this work, a Co catalyst supported on the Si 4 Al 2 O 2 N 6 solid solution of Si 3 N 4 and Al 2 O 3 (Co/Si 4 Al 2 O 2 N 6) has been developed to effectively catalyze ESR reaction. Our results demonstrate that the Co/Si 4 Al 2 O 2 N 6 catalyst exhibits remarkably improved performances as compared with the Co/Si 3 N 4 and Co/Al 2 O 3 catalysts. In the Co/Si 4 Al 2 O 2 N 6 -catalyzed ESR reaction, ethanol conversion of 97 % has been achieved with hydrogen yield reaching 73 %. Long-time catalytic experiment manifests the Co/Si 4 Al 2 O 2 N 6 catalyst possesses excellent durability. X-ray photoelectron spectroscopy (XPS) studies reveal that the enhanced metal-support interaction (MSI) and charge transfer from Si 4 Al 2 O 2 N 6 support to Co species in the Co/Si 4 Al 2 O 2 N 6 catalyst confer lower valence state on the Co catalyst supported on Si 4 Al 2 O 2 N 6 , thus promoting the C–C bond cleavage capability, leading to high C1 product yield and boosting the hydrogen-production efficiency. The catalytic mechanism studies explored by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveal that the Co/Si 4 Al 2 O 2 N 6 exhibits a remarkable preference for C1 products over the Co/Si 3 N 4 and Co/Al 2 O 3 catalysts at low reaction temperature, thus resulting in high hydrogen-production efficiency with excellent catalytic durability. • Co/Si 4 Al 2 O 2 N 6 boosting hydrogen production from ethanol steam reforming. • Si 4 Al 2 O 2 N 6 solid solution of Al 2 O 3 and Si 3 N 4 conferring stronger metal-support interaction (MSI) on Co/Si 4 Al 2 O 2 N 6. • Regulating chemical state of Co catalysts via enhanced electron donation from Si 4 Al 2 O 2 N 6 support to Co species. • Mechanism investigation of catalytic ESR reaction by in situ DRIFTS studies. [ABSTRACT FROM AUTHOR]

Developing a high-performance Ni-based catalyst for ethanol steam reforming (ESR) reaction is desirable for sustainable hydrogen production. In this work, β-Si 4 Al 2 O 2 N 6 , the high-temperature solid solution of Si 3 N 4 and Al 2 O 3 , was utilized as support to fabricate Ni catalyst (Ni/Si 4 Al 2 O 2 N 6) for ESR reaction to enhance hydrogen-production efficiency. The catalytic experiments demonstrated that Ni/Si 4 Al 2 O 2 N 6 catalyst exhibited higher C–C bond cleavage capacity, hydrogen-production efficiency, catalytic durability and better anti-coke performance as compared with Ni/Si 3 N 4 and Ni/Al 2 O 3 catalysts. H 2 -TPR, XPS and NH 3 -TPD studies revealed that the stronger metal-support interaction (MSI) in Ni/Si 4 Al 2 O 2 N 6 catalysts induced more distinct charge transfer from Ni species to Si 4 Al 2 O 2 N 6 support, fabricating Ni active sites with higher oxidation state and achieving higher catalytic activity and durability for ESR reaction. [ABSTRACT FROM AUTHOR]

• Cobalt chemical state tuning via selective crystal facet exposure of CeO 2 support. • Improved catalytic activity and durability of catalyst with low state of Co sites. • In situ detection of intermediates of ESR reaction by SR-PIMS observation. • Catalytic ESR reaction mechanism investigated by in situ SR-PIMS and DFT studies. Regulating the chemical state of Co sites to develop high-performance Co-based catalysts for ethanol steam reforming reaction is desirable but challenging. Herein, we report an effective strategy of tuning chemical states of Co sites by preferred exposure of CeO 2 facets. The as-prepared Co/CeO 2 -(M) and Co/CeO 2 -(U) catalysts have exposure preference of (1 1 1) facet and (1 0 0) facet of CeO 2 supports, respectively. The results demonstrate that the Co/CeO 2 -(M) has Co sites in lower oxidation state and exhibits higher C C bond cleavage capability and more excellent catalytic performance for ethanol steam reforming reaction than Co/CeO 2 -(U), the hydrogen selectivity reaches as high as 97% at ethanol conversion of 100%. In situ synchrotron radiation photoionization mass spectrometry and density functional theory calculations reveal that Co site in low oxidation state has a significant preference for carbon chain shortening by C C cleavage over carbon chain lengthening by condensation reaction, thus improving the hydrogen production efficiency of ethanol steam reforming reaction. This work provides an effective strategy to enhance the catalytic performances of Co-based catalysts for ethanol steam reforming reaction and expands the understanding about ethanol steam reforming reaction mechanism. [ABSTRACT FROM AUTHOR]

Complex preparation, risky storage, and expensive transportation are hindering the application of hydrogen (H 2) energy. To overcome these, a simple, cost-effective, and zero CO 2 -emission method is urgently needed. This study for the first time showed that the aluminum-ethanol (Al-ethanol) reaction without the need of complex pre-treatment can produce simultaneously hydrogen, aluminum ethoxide [Al(EtO) 3 ], and supported metallic nanoparticle (NP) catalyst. Fe (3.6 nm), Co (3.5 nm), Ni (2.9 nm), and Cu (3.5 nm) NPs, in-situ generated by the galvanic replacement reaction between aluminum and metal ions, provided the catalytically active sites for the Al-ethanol reaction, effectively enhancing H 2 and Al(EtO) 3 formation. Consequently, the Al-ethanol reaction catalyzed by the Ni NPs with the smallest average size at 50 °C led to the formation of hydrogen at a high rate of 109 mL-H 2 ·min−1·g-Al−1. Density functional theory (DFT) calculations suggested that the in-situ generated Ni NPs had charge transfer with ethanol and aluminum, which significantly enhanced the ethanol adsorbing capability onto the aluminum. Moreover, recovery of high value-added Al(EtO) 3 and utilization of supported metallic catalyst could additionally benefit the practical application of the Al-ethanol reaction. With the proposed "three eagles with one arrow" strategy, simultaneous generation of H 2 , Al(EtO) 3 and supported metallic catalyst could be readily realized in a more straightforward, scalable and economical way. [Display omitted] • The Al-ethanol-NiCl 2 reaction was firstly developed to efficiently produce H 2. • Metallic nanoparticles in-situ formed sufficiently catalyze Al-ethanol reaction. • The work simultaneously produced H 2 , aluminum ethoxide and supported metallic catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boosting cobalt-catalyzed ethanol steam reforming for hydrogen production. • Donation of electron density from concomitant O 2 2− to Co/La 0.25 Ce 0.75 O 1.88 catalyst. • Regulation of valence state and reducibility of Co catalysts via La doping in CeO 2. • Investigation of catalytic ESR reaction mechanism by in situ DRIFTS studies. Tuning the valence state and reducibility of Co active site in Co-based catalysts to improve catalytic performances is desirable for hydrogen production from ethanol steam reforming (ESR) reaction. In this work, we fabricate Co/La x Ce 1−x O 2−x/2 (x = 0.5, 0.25, 0.17) catalysts and investigate their catalytic performances for ESR reaction. Our studies manifest that the catalytic performances of Co-based catalysts have been effectively improved by La doping in CeO 2. Among the investigated catalysts, Co/La 0.25 Ce 0.75 O 1.88 exhibits the highest catalytic activity and durability, the hydrogen yield reaches as high as 80 % at ethanol conversion of 100 %, with an excellent durability during long-time (58 h) catalytic experiment. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature programmed reduction (H 2 -TPR) studies demonstrate that the valence state and reducibility of the Co/La 0.25 Ce 0.75 O 1.88 are effectively regulated via donation of electron density from the concomitant peroxide anions in La 0.25 Ce 0.75 O 1.88 to the supported cobalt catalyst, the C C bond cleavage capability has been significantly enhanced to boost the hydrogen-production efficiency from ESR reaction. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies reveal that Co/La 0.25 Ce 0.75 O 1.88 shows a remarkable preference for producing C1 products, the Co species in low valence state and with high reducibility result in highly efficient C C cleavage and excellent catalytic durability. [ABSTRACT FROM AUTHOR]