Hydrogen gas is a storable form of chemical energy that could complement intermittent renewable energy conversion. One of the main disadvantages of hydrogen gas arises from its low density, and therefore, efficient handling and storage methods are key factors that need to be addressed to realize a hydrogen-based economy. Storage systems based on liquids, in particular, formic acid and alcohols, are highly attractive hydrogen carriers as they can be made from CO2 or other renewable materials, they can be used in stationary power storage units such as hydrogen filling stations, and they can be used directly as transportation fuels. However, to bring about a paradigm change in our energy infrastructure, efficient catalytic processes that release the hydrogen from these molecules, as well as catalysts that regenerate these molecules from CO2 and hydrogen, are required. In this review, we describe the considerable progress that has been made in homogeneous catalysis for these critical reactions, namely, the hy...

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols.

The utilization of fossil fuels has enabled an unprecedented era of prosperity and advancement of well-being for human society. However, the associated increase in anthropogenic carbon dioxide (CO2) emissions can negatively affect global temperatures and ocean acidity. Moreover, fossil fuels are a limited resource and their depletion will ultimately force one to seek alternative carbon sources to maintain a sustainable economy. Converting CO2 into value-added chemicals and fuels, using renewable energy, is one of the promising approaches in this regard. Major advances in energy-efficient CO2 conversion can potentially alleviate CO2 emissions, reduce the dependence on nonrenewable resources, and minimize the environmental impacts from the portions of fossil fuels displaced. Methanol (CH3OH) is an important chemical feedstock and can be used as a fuel for internal combustion engines and fuel cells, as well as a platform molecule for the production of chemicals and fuels. As one of the promising approaches, thermocatalytic CO2 hydrogenation to CH3OH via heterogeneous catalysis has attracted great attention in the past decades. Major progress has been made in the development of various catalysts including metals, metal oxides, and intermetallic compounds. In addition, efforts are also put forth to define catalyst structures in nanoscale by taking advantage of nanostructured materials, which enables the tuning of the catalyst composition and modulation of surface structures and potentially endows more promising catalytic performance in comparison to the bulk materials prepared by traditional methods. Despite these achievements, significant challenges still exist in developing robust catalysts with good catalytic performance and long-term stability. In this review, we will provide a comprehensive overview of the recent advances in this area, especially focusing on structure-activity relationship, as well as the importance of combining catalytic measurements, in situ characterization, and theoretical studies in understanding reaction mechanisms and identifying key descriptors for designing improved catalysts.

Recent Advances in Carbon Dioxide Hydrogenation to Methanol via Heterogeneous Catalysis.

Catalytic transformations of syngas (a mixture of H2 and CO), which is one of the most important C1-chemistry platforms, and CO2, a greenhouse gas released from human industrial activities but also a candidate of abundant carbon feedstock, into chemicals and fuels have attracted much attention in recent years. Fischer-Tropsch (FT) synthesis is a classic route of syngas chemistry, but the product selectivity of FT synthesis is limited by the Anderson-Schulz-Flory (ASF) distribution. The hydrogenation of CO2 into C2+ hydrocarbons involving C-C bond formation encounters similar selectivity limitation. The present article focuses on recent advances in breaking the selectivity limitation by using a reaction coupling strategy for hydrogenation of both CO and CO2 into C2+ hydrocarbons, which include key building-block chemicals, such as lower (C2-C4) olefins and aromatics, and liquid fuels, such as gasoline (C5-C11 hydrocarbons), jet fuel (C8-C16 hydrocarbons) and diesel fuel (C10-C20 hydrocarbons). The design and development of novel bifunctional or multifunctional catalysts, which are composed of metal, metal carbide or metal oxide nanoparticles and zeolites, for hydrogenation of CO and CO2 to C2+ hydrocarbons beyond FT synthesis will be reviewed. The key factors in controlling catalytic performances, such as the catalyst component, the acidity and mesoporosity of the zeolite and the proximity between the metal/metal carbide/metal oxide and zeolite, will be analysed to provide insights for designing efficient bifunctional or multifunctional catalysts. The reaction mechanism, in particular the activation of CO and CO2, the reaction pathway and the reaction intermediate, will be discussed to provide a deep understanding of the chemistry of the new C1 chemistry routes beyond FT synthesis.

New horizon in C1 chemistry: breaking the selectivity limitation in transformation of syngas and hydrogenation of CO2 into hydrocarbon chemicals and fuels

The high volumetric capacity (53 g H2/L) and its low toxicity and flammability under ambient conditions make formic acid a promising hydrogen energy carrier. Particularly, in the past decade, significant advancements have been achieved in catalyst development for selective hydrogen generation from formic acid. This Perspective highlights the advantages of this approach with discussions focused on potential applications in the transportation sector together with analysis of technical requirements, limitations, and costs.

Formic Acid as a Hydrogen Energy Carrier

The ever-increasing amount of anthropogenic carbon dioxide (CO2) emissions has resulted in great environmental impacts. The selective hydrogenation of CO2 to methanol, the first target in the liquid sunshine vision, not only effectively mitigates the CO2 emissions, but also produces value-added chemicals and fuels. This critical review provides a comprehensive view of the significant advances in heterogeneous catalysis for methanol synthesis through direct hydrogenation of CO2. The challenges in thermodynamics are addressed first. Then the progress in conventional Cu-based catalysts is discussed in detail, with an emphasis on the structural, chemical, and electronic promotions of supports and promoters, the preparation methods and precursors of Cu-based catalysts, as well as the proposed models for active sites. We also provide an overview of the progress in noble metal-based catalysts, bimetallic catalysts including alloys and intermetallic compounds, as well as hybrid oxides and other novel catalytic systems. The developments in mechanistic aspects, reaction conditions and optimization, as well as reactor designs and innovations are also included. The advances in industrial applications for methanol synthesis are further highlighted. Finally, a summary and outlook are provided.

State of the art and perspectives in heterogeneous catalysis of CO2 hydrogenation to methanol.

Conversion of CO2 to value-added chemicals has been a long-standing objective, and direct hydrogenation of CO2 to lower olefins is highly desirable but still challenging. Herein, we report a selective conversion of CO2 to lower olefins through CO2 hydrogenation over a ZnZrO/SAPO tandem catalyst fabricated with a ZnO-ZrO2 solid solution and a Zn-modified SAPO-34 zeolite, which can achieve a selectivity for lower olefins as high as 80–90% among hydrocarbon products. This is realized on the basis of the dual functions of the tandem catalyst: hydrogenation of CO2 on the ZnO-ZrO2 solid solution and lower olefins production on the SAPO zeolite. The thermodynamic and kinetic coupling between the tandem reactions enable the highly efficient conversion of CO2 to lower olefins. Furthermore, this catalyst is stable toward the thermal and sulfur treatments, showing the potential industrial application.

Highly Selective Conversion of Carbon Dioxide to Lower Olefins

Highly Selective Conversion of Carbon Dioxide to Aromatics over Tandem Catalysts

Hydrogen production from the dehydrogenation of formic acid (fa) is promising. most of the current catalysts for fa dehydrogenation are effective only in the presence of bases or additives. we report here newly developed iridium complexes containing conjugated n,n-diimine ligands for fa dehydrogenation in water without the addition of bases or additives. a turnover frequency (tof) of 487500h(-1) with [cp*ir(l1)cl]cl (l1=2,2-bi-2-imidazoline) at 90 degrees c and a turnover number (ton) of 2400000 with in situ prepared catalyst from [ircp*cl-2](2) and 2,2-bi-1,4,5,6-tetrahydropyrimidine (l2) at 80 degrees c were obtained, the highest values reported for fa dehydrogenation to date. a mechanistic study reveals that the formation of [ir-h] intermediate species is the rate-determining step in the catalytic cycle.

Unprecedentedly High Formic Acid Dehydrogenation Activity on an Iridium Complex with an N,N′‐Diimine Ligand in Water

Hydrogenation of CO2 to methanol utilizing the hydrogen from renewable energy sources offers a promising way to reduce CO2 emissions through the CO2 utilization as a carbon source. However, it is a...

Jijie Wang

Papers

Highly Selective Conversion of Carbon Dioxide to Lower Olefins

Highly Selective Conversion of Carbon Dioxide to Aromatics over Tandem Catalysts

Unprecedentedly High Formic Acid Dehydrogenation Activity on an Iridium Complex with an N,N′‐Diimine Ligand in Water

High-Performance MaZrOx (Ma = Cd, Ga) Solid-Solution Catalysts for CO2 Hydrogenation to Methanol

Atomically dispersed Ptn+ species as highly active sites in Pt/In2O3 catalysts for methanol synthesis from CO2 hydrogenation