Hydrogen peroxide (H2O2) is an environment‐friendly and efficient oxidant with a wide range of applications in different industries. Recently, the production of hydrogen peroxide through direct ...electrosynthesis has attracted widespread research attention, and has emerged as the most promising method to replace the traditional energy‐intensive multi‐step anthraquinone process. In ongoing efforts to achieve highly efficient large‐scale electrosynthesis of H2O2, carbon‐based materials have been developed as 2e− oxygen reduction reaction catalysts, with the benefits of low cost, abundant availability, and optimal performance. This review comprehensively introduces the strategies for optimizing carbon‐based materials toward H2O2 production, and the latest advances in carbon‐based hybrid catalysts. The active sites of the carbon‐based materials and the influence of coordination heteroatom doping on the selectivity of H2O2 are extensively analyzed. In particular, the appropriate design of functional groups and understanding the effect of the electrolyte pH are expected to further improve the selective efficiency of producing H2O2 via the oxygen reduction reaction. Methods for improving catalytic activity by interface engineering and reaction kinetics are summarized. Finally, the challenges carbon‐based catalysts face before they can be employed for commercial‐scale H2O2 production are identified, and prospects for designing novel electrochemical reactors are proposed.
The latest advances in carbon‐based hybrid catalysts toward hydrogen peroxide (H2O2) production are reviewed. In particular, the design of functional groups and the dependence of electrolyte pH play important roles to further improve the selectivity of H2O2 production via the oxygen reduction reaction.
Catalysts are at the heart of the hydrogen evolution reaction (HER) for the production of pure and clean hydrogen. For practical applications, the scalable synthesis of efficient HER catalysts, which ...work in both acidic and alkaline media, is highly desired. In this work, the mechanochemically assisted synthesis of a Ru catalyst with HER performance surpassing Pt in both acidic and alkaline media is reported. Mass production of this Ru catalyst can be achieved via a two‐step procedure: the mechanochemical reaction between graphite and dry ice produces edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP); mixing a Ru precursor and the CGnP in an aqueous medium introduces Ru ions, which coordinate on the CGnP. Subsequent annealing results in uniform Ru nanoparticles (≈2 nm) anchored on the GnP matrix (Ru@GnP). The efficient Ru@GnP catalyst can be easily powered by a single silicon solar cell using a wireless integration device. The self‐powered device exhibits robust hydrogen evolution under the irradiation of standard AM 1.5 solar light. This work provides a new opportunity for the low‐cost mass production of efficient and stable catalysts for practical applications.
The mechanochemically assisted synthesis of a ruthenium (Ru) on graphene nanoplatelet (GnP) catalyst is explored to demonstrate efficient and stable hydrogen evolution performance surpassing Pt in both acidic and alkaline media. The synthesis procedures start from uniform anchoring Ru ions on mechanochemically driven edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP) to produce Ru@CGnP, which becomes Ru@GnP after reduction and annealing.
Abstract
The one-step electrochemical synthesis of H
2
O
2
is an on-site method that reduces dependence on the energy-intensive anthraquinone process. Oxidized carbon materials have proven to be ...promising catalysts due to their low cost and facile synthetic procedures. However, the nature of the active sites is still controversial, and direct experimental evidence is presently lacking. Here, we activate a carbon material with dangling edge sites and then decorate them with targeted functional groups. We show that quinone-enriched samples exhibit high selectivity and activity with a H
2
O
2
yield ratio of up to 97.8 % at 0.75 V vs. RHE. Using density functional theory calculations, we identify the activity trends of different possible quinone functional groups in the edge and basal plane of the carbon nanostructure and determine the most active motif. Our findings provide guidelines for designing carbon-based catalysts, which have simultaneous high selectivity and activity for H
2
O
2
synthesis.
Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction (HER) catalysis. The HER reaction rate is a trade-off between hydrogen adsorption and desorption on the ...catalyst surface. Herein, we report the rational balancing of hydrogen adsorption/desorption by orbital modulation using introduced environmental electronegative carbon/nitrogen (C/N) atoms. Theoretical calculations reveal that the empty d orbitals of iridium (Ir) sites can be reduced by interactions between the environmental electronegative C/N and Ir atoms. This balances the hydrogen adsorption/desorption around the Ir sites, accelerating the related HER process. Remarkably, by anchoring a small amount of Ir nanoparticles (7.16 wt%) in nitrogenated carbon matrixes, the resulting catalyst exhibits significantly enhanced HER performance. This includs the smallest reported overpotential at 10 mA cm
(4.5 mV), the highest mass activity at 10 mV (1.12 A mg
) and turnover frequency at 25 mV (4.21 H
s
) by far, outperforming Ir nanoparticles and commercial Pt/C.
Ammonia, one of the most important synthetic feedstocks, is mainly produced by the Haber-Bosch process at 400-500 °C and above 100 bar. The process cannot be performed under ambient conditions for ...kinetic reasons. Here, we demonstrate that ammonia can be synthesized at 45 °C and 1 bar via a mechanochemical method using an iron-based catalyst. With this process the ammonia final concentration reached 82.5 vol%, which is higher than state-of-the-art ammonia synthesis under high temperature and pressure (25 vol%, 450 °C, 200 bar). The mechanochemically induced high defect density and violent impact on the iron catalyst were responsible for the mild synthesis conditions.
Abstract
Identification of active sites is one of the main obstacles to rational design of catalysts for diverse applications. Fundamental insight into the identification of the structure of active ...sites and structural contributions for catalytic performance are still lacking. Recently, X-ray absorption spectroscopy (XAS) and density functional theory (DFT) provide important tools to disclose the electronic, geometric and catalytic natures of active sites. Herein, we demonstrate the structural identification of Zn-N
2
active sites with both experimental/theoretical X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. Further DFT calculations reveal that the oxygen species activation on Zn-N
2
active sites is significantly enhanced, which can accelerate the reduction of oxygen with high selectivity, according well with the experimental results. This work highlights the identification and investigation of Zn-N
2
active sites, providing a regular principle to obtain deep insight into the nature of catalysts for various catalytic applications.
A novel synthesis strategy is demonstrated to prepare Mo3P/Mo nanobelts with porous structure for the first time. The growth and formation mechanism of the porous Mo3P/Mo nanobelt structure was ...disclosed by varying the contents of H2/PH3 and the reaction temperature. During the hydrogen evolution reaction (HER) catalysis, the optimized porous Mo3P/Mo nanobelts exhibited a small overpotential of 78 mV at a current density of 10 mA cm−2 and a low Tafel slope of 43 mV dec−1, as well as long‐term stability in alkaline media, surpassing Pt wire. Density functional theory (DFT) calculations reveal that the H2O dissociation on the surface of Mo3P is favorable during the HER.
A novel synthesis strategy is designed to prepare Mo3P/Mo nanobelts with porous structure for the first time. During the hydrogen evolution reaction (HER), the optimized porous Mo3P/Mo nanobelts exhibited superb catalytic activity and stability in alkaline media, surpassing Pt wire.
Controllable synthesis of monolayer MoS2 is essential for fulfilling the application potentials of MoS2 in optoelectronics and valleytronics, etc. Herein, we report the scalable growth of high ...quality, domain size tunable (edge length from ∼200 nm to 50 μm), strictly monolayer MoS2 flakes or even complete films on commercially available Au foils, via low pressure chemical vapor deposition method. The as-grown MoS2 samples can be transferred onto arbitrary substrates like SiO2/Si and quartz with a perfect preservation of the crystal quality, thus probably facilitating its versatile applications. Of particular interest, the nanosized triangular MoS2 flakes on Au foils are proven to be excellent electrocatalysts for hydrogen evolution reaction, featured by a rather low Tafel slope (61 mV/decade) and a relative high exchange current density (38.1 μA/cm2). The excellent electron coupling between MoS2 and Au foils is considered to account for the extraordinary hydrogen evolution reaction activity. Our work reports the synthesis of monolayer MoS2 when introducing metal foils as substrates, and presents sound proof that monolayer MoS2 assembled on a well selected electrode can manifest a hydrogen evolution reaction property comparable with that of nanoparticles or few-layer MoS2 electrocatalysts.
Hydrogen is a promising clean energy source, an alternative to fossil fuels, and can potentially play a crucial role in reducing carbon emissions. The transportation and storage of hydrogen are the ...biggest hurdles to realizing a hydrogen economy. Ammonia is considered to be one of the most promising hydrogen carriers, because of its high hydrogen content and easy liquefaction in mild conditions. To date, ammonia is mostly produced by the ‘thermocatalytic’ Haber‐Bosch process, which requires high temperature and pressure. As a result, it can only produce ammonia in ‘centralized’ manufacturing systems. Mechanochemistry, a newly emerging method for efficient ammonia synthesis, offers potential advantages over the Haber‐Bosch process. Mechanochemical ammonia synthesis under near ambient conditions can be connected with ‘localized’ sustainable energy systems. In this perspective, the state‐of‐the‐art mechanochemical ammonia synthesis processes will be introduced. Challenges and opportunities are also discussed in relation to its role in a hydrogen economy.
Mechanochemical ammonia synthesis: Mechanochemistry is an emerging method of ammonia synthesis under mild conditions, and has no carbon emissions when connected with sustainable energy systems. In this perspective, the state‐of‐the‐art methods of mechanochemical ammonia synthesis are introduced with their challenges and opportunities for further development.
Developing high‐efficiency and cost‐effective alloy catalysts toward hydrogen‐evolution reaction (HER) is crucial for large‐scale hydrogen production via electrochemical water splitting, but ...conventional single‐principal‐element alloy design usually causes insufficient activity and durability of state‐of‐the‐art multimetallic catalysts based on non‐precious transition metals. Herein, we report multicomponent intermetallic Mo(NiFeCo)4 nanoparticles seamlessly integrated on hierarchical nickel network (Mo(NiFeCo)4/Ni) as robust hydrogen‐evolution electrocatalysts with remarkably improved activity and durability by making use of iron and cobalt atoms partially substituting nickel sites to form high‐entropy NiFeCo sublattice in intermetallic MoNi4 matrix, which serve as bifunctional electroactive sites for both water dissociation and adsorption/combination of hydrogen intermediate and improves thermodynamic stability. By virtue of bicontinuous nanoporous nickel skeleton facilitating electron/ion transportation, self‐supported nanoporous Mo(NiFeCo)4/Ni electrode exhibits exceptional HER electrocatalysis, with low Tafel slope (≈35 mV dec−1), high current density (≈2300 mA cm−2) at low overpotential (200 mV) and long‐term durability in 1 m KOH. When coupled to its electrooxidized and nitrified derivative for oxygen‐evolution reaction, their alkaline water electrolyzers operate with a superior overall water‐splitting output, outperforming the one constructed with commercially available noble‐metal‐based catalysts. These electrochemical properties make it an attractive candidate as electrocatalyst in alkaline water electrolysis for large‐scale hydrogen generation.
Multicomponent intermetallic Mo(NiFeCo)4 nanoparticles that are seamlessly integrated on hierarchical nanoporous nickel network (Mo(NiFeCo)4/Ni) hold great promise as low‐cost verstile electrocatalysts for highly efficient water splitting. Associated with hierarchical nanoporous architecture to facilitate electron transfer and offer abundant multicomponent intermetallic active sites, the self‐supported nanoporous Mo(NiFeCo)4/Ni electrode and its electrooxidized/nitrified derivative exhibit remarkably enhanced hydrogen‐evolution and oxygen‐evolution activities and durability.
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