Integration of morphology and electronic structure modulation on cobalt phosphide nanosheets to boost photocatalytic hydrogen evolution from ammonia borane hydrolysis

The controllable and safe hydrogen storage technologies are widely recognized as the main bottleneck for the accomplishment of sustainable hydrogen energy.Ammonia borane(AB)has regarded as a competitive candidate for chemical hydrogen storage.However,developing efficient yet high-performance catalysts towards hydrogen evolution from AB hydrolysis remains an enormous challenge.Herein,cobalt phosphide nanosheets are synthesized by a facile salt-assisted along with low-temperature phosphidation strategy for simultaneously modulating its morphology and electronic structure,and function as hydrogen evolution photocatalysts.Impressively,the Co_(2)P nanosheets display extraordinary performance with a record high turnover frequency of 44.9 min^(-1),outperforming most of the noble-metal-free catalysts reported to date.This remarkable performance is attributed to its desired nanosheets structure,featuring with high specific surface area,abundant exposed active sites,and short charge diffusion paths.Our findings provide a novel strategy for regulating metal phosphides with desired phase structure and morphology for energy-related applications and beyond.

Anomalous metastable hcp Ni nanocatalyst induced by non-metal N doping enables promoted ammonia borane dehydrogenation

Developing high-performing non-noble transition metal catalysts for H_(2) evolution from chemical hydrogen storage materials is of great significance for the hydrogen economy system, yet challenging. Herein,we present for the first time that anomalous metastable hexagonal close-packed Ni nanoparticles induced by heteroatom N doping encapsulated in carbon(N-hcp-Ni/C) can exhibit admirable catalytic performance for ammonia borane(AB) dehydrogenation, prominently outperforming conventional fcc Ni counterpart with similar morphology and favorably presenting the state-of-the-art level.Comprehensive experimental and theoretical studies unravel that unusual hcp phase engineering of Ni together with N doping could induce charge redistribution and modulate electronic structure, thereby facilitating H_(2)O adsorption and expediting H_(2)O dissociation(rate-determining step). As a result, AB dehydrogenation can be substantially boosted with the assistance of N-hcp-Ni/C. Our proposed strategy highlights that unconventional crystal phase engineering coupled with non-metal heteroatom doping is a promising avenue to construct advanced transition metal catalysts for future renewable energy technologies.

A step‐growth strategy to grow vertical porous aromatic framework nanosheets on graphene oxide:Hybrid material‐confined Co for ammonia borane methanolysis

The rational synthesis of a two-dimensional(2D)porous aromatic framework(PAF)with a controllable growth direction remains a challenge to overcome the limitation of traditional stacked 2D materials.Herein,a step-growth strategy is developed to fabricate a vertically oriented nitrogen-rich porous aromatic framework on graphene oxide(V-PAF-GO)using monolayer benzidine-functionalized GO(BZ-GO)as a molecular pillar.Then,the confined Co nanoparticle(NP)catalysts are synthesized by encapsulating ultra-small Co into the slit pores of V-PAF-GO.Due to the high nitrogen content,large specific surface area,and adequate slit pores,the optimized vertical nanocomposites V-PAF-GO provide abundant anchoring sites for metal NPs,leading to ultrafine Co NPs(1.4 nm).The resultant Co/V-PAF-GO catalyst shows an extraordinary catalytic activity for ammonia borane(AB)methanolysis,yielding a turnover frequency value of 47.6 min−1 at 25°C,comparable to the most effective non-noble-metal catalysts ever reported for AB methanolysis.Experimental and density functional theory studies demonstrate that the electron-donating effect of N species of PAF positively corresponds to the low barrier in methanol molecule activation,and the cleavage of the O–H bond in CH3OH has been proven to be the rate-determining step for AB methanolysis.This work presents a versatile step-growth strategy to prepare a vertically oriented PAF on GO to solve the stacking problem of 2D materials,which will be used to fabricate other novel 2D or 2D–2D materials with controllable orientation for various applications.

Ammonia borane-enabled hydrogen transfer processes:Insights into catalytic strategies and mechanisms

Transfer hydrogenation(TH) with in situ generated hydrogen donor is of great importance in reduction reactions, and an alternative strategy to traditional hydrogenation processes involving pressurized molecular hydrogen. Ammonia borane(NH3BH3, AB) is a promising material of hydrogen storage, and it has attracted much attention in reductive organic transformations owing to its high activity, good atom economy, nontoxicity, sustainability, and ease of transport and storage. This review focuses on summarizing the recent progress of AB-mediated TH reactions of diverse substrates including nitro compounds, nitriles, imines, alkenes, alkynes, carbonyl compounds(ketones and aldehydes), carbon dioxide,and N-and O-heterocycles. Syntheses protocols(metal-containing and metal-free), the effect of reaction parameters, product distribution, and variation of reactivity are surveyed, and the mechanism of each reaction involving the action mode of AB as well as structure-activity relationships is discussed in detail. Finally, perspectives are presented to highlight the challenges and opportunities for AB-enabled TH reactions of unsaturated compounds.

Interface electron collaborative migration of Co–Co3O4/carbon dots:Boosting the hydrolytic dehydrogenation of ammonia borane

Ammonia borane(AB)is an excellent candidate for the chemical storage of hydrogen.However,its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts.Herein,we report Co-Co3O4 nanoparticles(NPs)facilely deposited on carbon dots(CDs)as a highly efficient,robust,and noble-metal-free catalyst for the hydrolysis of AB.The incorporation of the multiinterfaces between Co,Co3O4 NPs,and CDs endows this hybrid material with excellent catalytic activity(rB=6816 mLH2 min^-1 gCo^-1)exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems.A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules,resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate.

Carbon dots-confined CoP-CoO nanoheterostructure with strong interfacial synergy triggered the robust hydrogen evolution from ammonia borane

Ammonia borane(NH_(3)BH_(3),AB) is promising for chemical hydrogen sto rage;however,current systems for rapid hydrogen production are limited by the expensive noble metal catalysts required for AB hydrolysis.Here we report the design and synthesis of a highly efficient and robust non-noble-metal catalyst for the hydrolysis of AB at 298 K(TOF=89.56 molH_(2) min^(-1) molCo^(-1)).Experiments and density functional theory calculations were performed to explore the catalyst’s hybrid nanoparticle heterostructure and its catalytic mechanism.The catalyst comprised nitrogen-doped carbon dots confining CoO and CoP,and exhibited strong interface-induced synergistic catalysis for AB hydrolysis that effectively decreased the energy barriers for the dissociation of both AB and water molecules.The co-doping of N and P introduced numerous defects,and further regulated the reactivity of the carbon layers.The heterogeneous interface design technique presented here provides a new strategy for developing efficient and inexpensive non-noblemetal catalysts that may be applicable in other fields related to energy catalysis.

Co-CoO_x supported onto TiO_(2) coated with carbon as a catalyst for efficient and stable hydrogen generation from ammonia borane

Ammonia borane(AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article, catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO_(2)@N-C(CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoO_x/TiO_(2)@N-C(COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 m L min^(-1) g_(Co)^(-1) is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co, Co_(3)O_(4) and TiO_(2) promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Core-shell structured nanospheres with mesoporous silica shell and Ni core as a stable catalyst for hydrolytic dehydrogenation of ammonia borane

Core-shell structured nanospheres with mesoporous silica shell and Ni core(denoted as Ni@meso-SiO2) are prepared through a three-step process. Monodispersed Ni precursors are first prepared, and then coated with mesoporous SiO2. Final Ni@meso-SiO2spheres are obtained after calcination. The products are characterized by X-ray powder diffraction, transmission electron microscopy and N2adsorption-desorption methods. These spheres have a high surface area and are well dispersed in water, showing a high catalytic activity with a TOF value of 18.5,and outstanding stability in hydrolytic dehydrogenation of ammonia borane at room temperature.

Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media

Ammonia borane is widely used in most areas including fuel cell applications.The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles.The glassy carbon electrode was firstly covered with polymeric film electrochemically and then,Au,Ag,and Au–Ag nanoparticles were deposited on the polymeric film,respectively.The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy,transmission electron microscopy,electrochemical impedance spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.It was found that alloyed Au–Ag bimetallic nanoparticles are formed.Electrochemical measurements indicate that the developed electrode modified by Au–Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media.The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane.Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions.

Constructing ultrafine monodispersed Co_(2)P/(0.59-Cu_(3)P)on Cu doped CoZn-ZIF derived porous N-doped carbon for highly efficient dehydrogenation of ammonia borane

Rational construction of highly dispersed,small size,low cost catalysts for release of hydrogen from ammonia borane(AB)is regarded as a prospective approach for promoting the development of upcoming hydrogen economy.However,the high price and scarcity of precious metal catalysts impose restrictions on their large-scale application.To this end,with the aid of a Cu doped CoZn-zeolitic imidazolate frameworks(ZIFs)template strategy,we successfully construct ultrafine monodispersed Co_(2)P/(0.59-Cu_(3)P)on CoZn-ZIF derived porous N-doped carbon(Co_(2)P/(0.59-Cu_(3)P)-NC)as an efficient non-noble-metal catalyst.Specifically,Co and Cu atoms can be geometrically separated to high degree due to the presence of Zn in the CuCoZn-ZIF precursor,evaporation of Zn during pyrolysis can generate porous structure with the framework well maintained.The results show that porous Co_(2)P/(0.59-Cu_(3)P)-NC bimetallic phosphide exhibits large specific surface area,hierarchical pore structure,well-exposed active sites.Based on the kinetics analyses and ion effects,the catalyst has achieved an unprecedentedly high total turnover frequency(TOF)of 798 mol·molcat^(−1)·min^(−1)in 0.4 M NaOH solution at 298 K,which surpasses all the ever-reported transition-metal phosphides catalysts for hydrogen generation from AB.Experiments and theoretical studies confirm that the highly porous structure of the support,the ultrafine and high dispersion of nanoparticles,the N/P doping and their synergistic effects(e.g.,M-P,M-N,N-C,M-M',M-support)jointly induce strong electron transfer,which can reduce the reaction energy barrier and enhance their interaction with AB,thus correspondingly obtaining excellent catalytic performance.The mechanism and strategy presented in this work pave an avenue for the design of non-noble metal catalyst for hydrogen energy system.

A review on hydrogen production from ammonia borane:Experimental and theoretical studies

Ammonia borane(NHsBH3,AB)is an ideal raw material of hydrogen production with higher hydrogen storage capacity.In this paper,the catalytic processes of AB dehydrogenation were described from different ways,including thermal dehydrogenation,hydrolysis,methanolysis,photocatalysis and photopiezoelectric synergy catalysis with experimental research and theoretical calculations.Catalyst models include bulk materials,two-dimensional materials,nanocluster particles and single/diatomic structures.Among them,the proportion of H2 released is different,and the reaction conditions are also different,which are suitable for different application scenarios.Through this review,we could have a preliminary comprehensive understanding of AB dehydrogenation reaction.

Heterostructuring 2D Co_(2)P nanosheets with 0D CoP via a saltassisted strategy for boosting hydrogen evolution from ammonia borane hydrolysis

Ammonia borane(NH3BH3,AB)holds promise for chemical storage of hydrogen.However,designing superb and low-cost photocatalyst to drive hydrogen evolution from AB under visible light irradiation is highly desirable but remains a major challenge for promoting the practical utilization of AB.Herein,we demonstrated a heterostructure photocatalyst consisting of zerodimensional(0D)CoP nanoparticles immobilized on two-dimensional(2D)Co_(2)P nanosheets(CoP/Co_(2)Ps)as a high-performance and low-cost catalyst for hydrogen evolution from AB hydrolysis,in which 0D/2D heterostructure was synthesized using the saltinduced phase transformation strategy.Interestingly,the optimized CoP/Co_(2)Ps exhibit a robust H_(2) evolution rate of 32.1 L∙min^(−1)∙g_(Co)^(−1),corresponding to a turnover frequency(TOF)value of 64.1 min^(−1),being among the highest TOF for non-noblemetal catalysts ever reported,even outperforming some precious metal catalysts.This work not only opens a new avenue to accelerate hydrogen evolution from AB by regulating the electronic structures of heterointerfaces,but also provides a novel strategy for the construction of precious-metal-free materials for hydrogen-related energy catalysis in the future.

Facile synthesis of graphene-supported Ni-CeOx nano-composites as highly efficient catalysts for hydrolytic dehydrogenation of ammonia borane

Development of low-cost and high-performance catalysts for hydrogen generation via hydrolysis of ammonia borane （NH3BH3, AB） is a highly desirable pathway for future hydrogen utilization. In this work, Ni nanocatalysts doped with CeOx and supported on graphene （Ni-CeOdgraphene） were synthesized via a facile chemical reduction route and applied as robust catalysts for the hydrolysis of AB in aqueous solution at room temperature. The as-synthesized Ni-CeOdgraphene nanocomposites （NCs） exhibited excellent catalytic activity with a turnover frequency （TOF） as high as 68.2 min-1, which is 49-fold higher than that for a simple Ni nanoparticle catalyst and is among the highest values reported for non-noble metal catalysts in AB hydrolysis. The development of efficient and low-cost Ni-CeOdgraphene catalysts enhances the feasibility of using ammonia borane as a chemical hydrogen storage material, which may find application in a hydrogen fuel-cell based economy.

Three-dimensional nitrogen-doped graphene hydrogel supported Co-CeOx nanoclusters as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

The development of highly active noble-metal-flee catalysts for catalytic hydrolysis of ammonia borane is mandatory for its application in hydrogen storage. Herein, Co-CeOx nanoclusters have been successfully anchored on a three-dimensional nitrogen-doped graphene hydrogel （NGH） by a simple coreduction method and further used as efficient catalysts to catalytic hydrolysis of ammonia borane at room temperature. Thanks to the strong synergistic electronic effect between Co and CeOx, as well as the strong metal-support interaction between Co-CeOx and 3D NGH, the as-synthesized Co-（CeOx）0.91/NGH catalyst exhibits superior catalytic activity toward hydrolysis of ammonia borane, with the turnover frequency （TOF） value of 79.5 min 1, which is almost 13 times higher than that of Co]NGH, and higher than most of the reported noble-metal-free catalysts.

Hydrolytic dehydrogenation of ammonia borane catalyzed by poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets supported Ag_(0.3)Co_(0.7) nanoparticles

Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets(PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7nanoparticles in order to obtain an excellent catalyst for ammonia borane(AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag0.3Co0.7bimetallic nanoparticles with uniform size distribution of 5 nm are well dispersed on PAMAM/rGO composite architecture. Ag0.3Co0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value(TOF) of 19.79 molH2min-1molM-1at 25.0±0.1℃ and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy(34.21 kJ mol-1) make these Ag0.3Co0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.

Hydrogen generation of ammonia borane hydrolysis catalyzed by Fe_(22)@Co_(58) core-shell structure

In this paper,the process of ammonia borane(AB)hydrolysis generate H_(2) on the transition metal Fe@Co core-shell structure has been obtained.According to the different roles played by H_(2)O molecules and the number of H_(2)O molecules involved,there are three schemes of reaction paths.RouteⅠdoes not involve the dissociation of H_(2)O molecules and all H atoms come from AB.Moreover,the H_(2)O molecule has no effect on the breaking of the B—H bond or the N—H bond.The reaction absorbs more heat during the formation of the second and third H_(2) molecules.RouteⅡincludes the dissociation of H_(2)O molecules and the cleavage of B—H or N—H bonds,respectively,and the reaction shows a slight exotherm.RouteⅢstarted from the break of the B—N bond and obtained 3H_(2) molecules through the participation of different numbers of H_(2)O molecules.After multiple comparative analyses,the optimal hydrolysis reaction path has been obtained,and the reaction process can proceed spontaneously at room temperature.

Oxygen modified CoP2 supported palladium nanoparticles as highly efficient catalyst for hydrolysis of ammonia borane

Ammonia borane(AB)is regarded as a promising chemical hydrogen-storage material due to its high hydrogen content,nontoxicity,and long-term stability under ambient temperature.However,constructing advanced catalysts to further promote the hydrogen production still remains a challenge for the hydrolysis of AB.Herein,we report a novel oxygen modified CoP_(2)(O-CoP_(2))material with dispersed palladium nanoparticles(Pd NPs)as a highly efficient and sustainable catalyst for AB hydrolysis.The modification of oxygen could optimize the catalytic synergy effect between CoP_(2)and Pd NPs,achieving enhanced catalytic activity with a turnover frequency(TOF)number of 532 min^(-1)and an activation energy(E_(a))value of 16.79 kJ·mol^(-1).Meanwhile,reaction kinetic experiments prove that the activation of water is the rate-determining step(RDS).The water activation mechanism is revealed by quasi in-situ X-ray photoelectron spectroscopy(XPS)and in-situ X-ray absorption fine structure(XAFS)measurements.The activation of water leads to the production of-H and-OH groups,which are further adsorbed on the oxygen atoms in P-O bond and Pd atoms,respectively.In addition,density functional theory(DFT)calculations indicate that the introduced oxygen facilitates the adsorption and activation of water molecules.This novel modulation strategy successfully sheds new light on the development of advanced catalysts for hydrolysis of AB and beyond.

Monodispersed Pt nanoparticles on reduced graphene oxide by a non-noble metal sacrificial approach for hydrolytic dehydrogenation of ammonia borane

Downsizing noble metal nanoparticles,such as Pt,is an essential goal for many catalytic reactions.A non-noble metal sacrificial approach was used to immobilize monodispersed Pt nanoparticles （NPs） with a mean size of 1.2 nm on reduced graphene oxide （RGO）.ZnO co-precipitated with Pt NPs and subsequently sacrificed by acid etching impedes the diffusion of Pt atoms onto the primary Pt particles and also their aggregation during the reduction of precursors.The resulting ultrafine Pt nanoparticles exhibit high activity （a turnover frequency of 284 min-1 at 298 K） in the hydrolytic dehydrogenation of ammonia borane.The non-noble metal sacrificial approach is demonstrated as a general approach to synthesize well-dispersed noble metal NPs for catalysis.

Enhanced catalytic activity of monodispersed AgPd alloy nanoparticles assembled on mesoporous graphitic carbon nitride for the hydrolytic dehydrogenation of ammonia borane under sunlight

We address the composition-controlled synthesis of monodispersed AgPd alloy nanoparticles （NPs）, their assembly for the first time on mesoporous graphitic carbon nitride （mpg-C3N4）, and the unprecedented catalysis of mpg-CgN4@AgPd in the hydrolytic dehydrogenation of ammonia borane （AB） at room temperature. Monodispersed AgPd alloy NPs were synthesized using a high-temperature organic-phase surfactant-assisted protocol comprising the co-reduction of silver（I） acetate and palladium（II） acetylacetonate in the presence of oleylamine, oleic acid, and 1-0ctadecene. This protocol allowed the synthesis of four different compositions of AgPd alloy NPs. The AgPd alloy NPs were then assembled on mpg-C3N4, reduced graphene oxide, and Ketjenblack using a liquid-phase self-assembly method. Among the three supports tested, the mpg-CBN4@AgPd catalysts provided the best activity because of the Mott-Schottky effect, which was driven by the favorable work function difference between mpg-CBN4 and the metal NPs. Moreover, the activity of the mpg-CBN4@AgPd catalyst was further enhanced by an acetic acid treatment （AAt）, and a record initial turnover frequency of 94.1 mOl（hydrogen）＇mOl（catalyst）-l-min-1 was obtained. Furthermore, the mpg-CBN4@Ag42Pdss-AAt catalyst also showed moderate durability for the hydrolysis of AB. This study also includes a wealth of kinetic data for the mpg-CBN4@AgPd-catalyzed hydrolysis of AB.

An efficient single atom catalysts Os/P_(3)C sheet for ammonia borane dehydrogenation

Ammonia borane(NH_(3)BH_(3),AB)has been considered to be a promising chemical hydrogen storage material.Based on density functional theory,a series of transition metal atoms supported P_(3)C(P_(3)C_O)sheet is systematically investigated to screen out the most promising catalyst for dehydrogenation of AB.The results indicate that the Os/P_(3)C and Os/P_(3)C_O could be an efficient single atom catalyst(SACs)and the stepwise reaction pathway with free energy barrier of 2.07 and 1.54 e V respectively.Remarkably,the rate constant further quantitatively confirmed the real situation of the first step of dehydrogenation of AB on the Os/P_(3)C and Os/P_(3)C_O substrates.We found that k_(f1)at 400 K is equivalent to k_(f2)at 800 K,which greatly improves the temperature of the first step of AB dehydrogenation on P_(3)C_O.We hope this work can provide a promising method for the design of catalysts for AB dehydrogenation reactions on the surface of two-dimensional materials(2D).