Facile Synthesis and Electrochemical Characterization of Pt and Pt-based Electrocatalysts Supported on Reduced Graphene Oxide

Effect of carbon substrate materials as a Pt–Ru catalyst support on the performance of direct methanol fuel cells

Characterization and performance evaluation of Pt–Ru electrocatalysts supported on different carbon materials for direct methanol fuel cells

This special issue on clean energy and environmental technologies aims at providing a forum for researchers who are working on relevant areas to exchange ideas driving innovation and report their latest research outcomes in developing clean energy and environmental technologies. A few years ago, Nobel Laureate Richard E. Smalley outlined Humanity’s Top Ten Problems for the next fifty years, in a talk given for the Enterprise Forum at Massachusetts Institute of Technology (MIT). Energy was listed as the first of the top ten problems and the environment as the fourth. Actually energy is the most basic requirement for economic development and people’s livelihoods while this requirement is constantly increasing, particularly in economically rapidly developing countries like China. Supply of energy still mainly relies on fossil fuels such as coal, petroleum, and natural gas around the world. However reserves for fossil fuels are limited and producing energy from these fossil fuels with existing technologies has caused serious environmental problems, e.g., increasing greenhouse gases emission which exacerbates global warming. Resolutions to these global problems lie in the innovative technologies to produce energy in a clean and environmentally friendly manner. Both developing renewable energy and using energy more efficiently are major components of clean energy and environmental technologies. Development of clean energy and environmental technologies has been thought of as two of the most active research fields today. This special issue includes 12 papers consisting of research and review articles selected from different research institutions in Australia, China and Indonesia. They contain a wide range of the hottest research topics in clean energy and environmental technologies, including development of the innovative catalysts used for clean energy and environmental processes, studies on hydrogen production and storage, CO2 capture and syngas clean technology as well as other research in energy efficiency, coal seam gas recovery and environmental economics. These research and/or review articles, which although do not cover the full scope of studies in energy and environment due to page limitations , can still provide readers with brief track references to facilitate the development of new clean energy and environmental technologies. This special issue was organized as per instructions of the Editors Dr. Fei Yuan, Prof. Yaodong Huang, and Prof. Yanni Li. We have received invaluable help from colleagues working with or having worked with clean energy and environmental research, especially Prof. Edward White, Prof. Duong Do, Dr. Greg Birkett and Dr. Fu-Yang Wang in School of Chemical Engineering, the University of Queensland. They provided careful peer-reviews on the selected papers with many useful comments and suggestions for authors to enhance the quality of the papers. It would be impossible to publish this special issue without the help of these peer-reviewers. Finally, as the Guest Editor, I would like to thank all the people—all the authors and co-authors and reviewers for their contributions to this special issue, and editors of the Frontiers of Chemical Science and Engineering for their scientific input and consistent support.

The development and diffusion of clean technologies has an important role to play in preventing pollution. Government must address the issue of how firms can be given the necessary incentive to develop environmentally sound production techniques and products. This paper focus on how subsidies can — under certain restrictive conditions — stimulate innovation. Subsidization is usually assumed to involve unit subsidies for pollution reduction. Unit subsidies have little to do with the subsidy schemes in actual use. Our focus is on subsidy schemes specifically designed to promote the development of clean technologies through the use of grants/financial aid. Based on data from the development projects initiated through The Danish Clean Technology Programme we analyze how environmental innovations take place when the polluters, their suppliers and consultants are actively engaged in the development processes. The main merit of subsidy schemes like the Danish one is its direct focus on the innovation processes and the active incorporation of the network of firms surrounding the polluters. Our findings lead us to conclude that when it comes to subsidization, the role of government should be redefined. Government can act as a “matchmaker” by providing firms with informative incentives and necessary contacts for finding more efficient technological solutions to specific environmental problems.

Argues that access to clean, affordable, and reliable energy sources promotes economic prosperity. Clean energy technologies, such as carbon capture and sequestration as well as green hydrogen, are catalysts of the fundamental transformation process towards a more sustainable production. As clean energy is cautiously introduced into the global energy mix, fossil fuels, which once dominated the composition, are diminishing in their significance. This phenomenon is rewarding both economically and environmentally, given that fossil fuels are finite in nature and release toxic emissions when burned. Further, as clean energy technologies produce no carbon emissions in generating electricity, its adoption will enable us to achieve our ambitious climate policy goals. Finally, clean energy technologies are driving forces of energy-based economic development—promoting energy security and sustainable economic development concurrently. As such, it is found that the development of specific clean energy technologies is the best solution if we are aiming to combat global climate change and pursue economic-development sustainably. Hence, this chapter argues that policymakers ought to encourage the development of specific clean energy technologies. Nonetheless, the chapter acknowledges that the developmental process of these technologies may come with several threats and further contends that these risks must be mitigated before the benefits of accelerating a low-carbon pathway can be reaped. Therefore, the author posits that policymakers will have to deliberately adopt measures in fostering greater global cooperation so as to institute a robust climate-finance mechanism. To that end, Audrey Loo Wan Yi provides a snapshot of the existing climate-finance mechanism and discusses how a results-based climate-finance framework could possibly be the way forward.

Development of electrocatalysts with extended homogeneity and improved metal–support interactions is of urgent scientific need in the context of electrochemical energy applications. Herein, bimetallic Pt–Pd nanoparticles with good homogeneity are fabricated using a convenient solution phase chemical reduction method onto a reduced graphene oxide (rGO) support. X-ray diffraction studies revealed that Pt–Pd/rGO possesses the crystallite size of 3.1 nm. The efficacies of Pt–Pd/rGO catalyst (20 wt% Pt + 10 wt% Pd on rGO support, Pt:Pd atomic ratio = 1:1) towards ethanol electrooxidation reaction (EOR) are evaluated in acidic conditions by cyclic voltammetry using catalyst-coated glassy carbon electrode as a working electrode. With the better dispersion on rGO support the Pt–Pd/rGO nancomposite catalyst exhibit highest mass specific activity (0.358 mA/µg-Pt) which is observed to be 1.9 times of similarly synthesized 20 wt% Pt/rGO (0.189 mA/µg-Pt) and 2.5 times of commercial 20 wt% Pt/C (0.142 mA/µg-Pt), respectively. Apart from the observed improved EOR activity, the Pt–Pd/rGO catalyst exhibited better stability than Pt/rGO and Pt/C catalysts. Strong synergy offered by Pt, Pd and rGO support could contribute to the observed higher EOR activity of Pt–Pd/rGO.

In the present work, we have synthesized a series of composites with NiO, Co3O4, and NiCo2O4 and reduced graphene oxide (RGO). The hybrid composites were fabricated trough a single step hydrothermal approach with subsequent heat treatment. X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy analyses indicate the metal oxide nanoparticles were integrated well in the carbon cloth substrate with rGO support. The as-prepared materials were evaluated as the electrodes for energy storage and conversion devices. As the electrode for supercapatteries, rGO supported NiCo2O4 exhibits highest specific capacity of 333 C g−1 at a specific current of 1 mA cm−1 when compared to their monometallic oxides and also exhibits excellent cycling stability with 89% retention at 5 mA cm−1 after 5000 cycles in a three-electrode system. Furthermore, we have investigated the electro-oxidation of methanol with these electrode in an alkaline medium. Compared to individual oxide composites, the NiCo2O4–rGO electrode shows excellent electro-catalytic activity towards methanol oxidation with low onset potential of ~ 0.3 V and high catalytic current density. The observed bi-functionality of rGO supported metal oxide composite could be attributed to the enhanced electrical conductivity and the well-integrated contact with carbon cloth back bone. Thereby it can be concluded that the design of hybrid composite electrode could be the better choice of electro-active materials for both energy storage and conversion applications.

Understanding improved thermal stability of lanthanum-modified Cu/CeO2-ZrO2 for CO oxidation under lean-burn exhaust conditions

One-pot synthesis of stable cationic gold species highly active in the CO oxidation confined into mordenite-like zeolite

With concerns about global warming and energy security, people are reducing fossil fuel use and turning to clean energy technologies. Mineral resources are used as materials for various energy technologies, and with the development of clean energy technologies, the demand for mineral resources will increase. China is a large country with various mineral resources, but its structural supply problem is severe. For China to reach the targets of carbon peaking before 2030 and carbon neutrality before 2060, they have set specific milestones for developing each clean energy industry; thus, the demand for mineral resources in clean energy will increase. We first summarise the mineral resources supply for China’s development of clean energy technologies. We analyse the demand for various mineral resources in specific clean energy technology sectors under the stated policies scenario and sustainable development scenario through scenario setting. Finally, we combine current domestic mineral resource reserves and overseas import channels to analyse China’s mineral resource supply and demand for developing the clean energy industry. Our results show that the surge in clean energy generation and electric vehicle ownership in China between 2020 and 2050 will lead to a significant increase in demand for mineral resources for these technologies and a shortage in the supply of some mineral resources. In particular, the supply of copper, nickel, cobalt, and lithium will be a severe constraint for clean energy development. We also find that secondary recycling of power battery materials in the electric vehicle sector could alleviate China’s resource constraints. The findings of our study provide a better understanding of the kinds of mineral elements that are in short supply on the path of clean energy development in China under carbon peaking and carbon neutrality targets and the future channels that can be used to increase the supply of minerals.

Synthesis of highly active Cobalt catalysts for low temperature CO oxidation

While CO oxidation catalyzed by gold nanoparticles has been practiced academically for several decades, there are still important discoveries to be made. One area of current interest is to pair Au with another alloying metal and observe the catalytic consequences of the presence of the other metal. In this work, TiO2-supported bimetallic Au nanoparticles are alloyed with Cu, Co, Ni, Pd, and Ru and used as catalysts for CO oxidation. Two synthetic methods for the alloys are presented: a strong electrostatic adsorption (SEA) method and a sterically demanding ligand synthesis (SDLS) method which uses triphenylphosphine (TPP) as the ligand. The catalytic performance of the materials synthesized with the SEA and SDLS methods is compared in CO oxidation. The results indicate that the materials tested present an enthalpy–entropy compensation effect. Interestingly, both the enthalpy of activation, ΔH‡, and the entropy of activation, ΔS‡, generally decrease with particle size. AuCo and AuRu materials exhibit a decrease in the overall activity as compared to Au and the other Au alloys when synthesized via SEA. Au face-centered-cubic alloys AuCu, AuNi, and AuPd prepared via SEA show an improvement in activity compared to monometallic Au in our reaction conditions. In situ diffuse reflectance infrared Fourier transform spectroscopy presents two distinct regions for Au bimetallics where AuCo and AuRu show peak positions in the region of 2070–2050 cm–1, indicating a weaker interaction for AuCo and AuRu with CO when compared to that of the other alloys. For the SDLS method samples, the hypothesis is that TPP would enhance the CO oxidation rate by enhancing the charge transfer to the metallic surface. The results indicate that SDLS samples have lower CO oxidation rates and if any charge transfer occurs, it is masked by the lateral interactions of the CO π bonds and the phenyl groups of TPP.

Platinum (Pt) is widely used as an activator in direct methanol fuel cells (DMFCs). However, the development of Pt catalyst is hindered due to its high cost and CO poisoning. A multi-metallic catalyst is a promising catalyst for fuel cells. We develop a simple and rapid method to synthesize PtNiCo/rGO nanocomposites (NCs). The PtNiCo/rGO NCs catalyst was obtained by microwave-assisted synthesis of graphene oxide (GO) with Pt, Ni, and Co precursors in ethylene glycol (EG) solution after heating for 20 min. The Pt-Ni-Co nanoparticles showed a narrow particle size distribution and were uniformly dispersed on the reduced graphene oxide without agglomeration. Compared with PtNiCo catalyst, PtNiCo/rGO NCs have superior electrocatalytic properties, including a large electrochemical active surface area (ECSA), the high catalytic activity of methanol, excellent anti-toxic properties, and high electrochemical stability. The ECSA can be up to 87.41 m2/g at a scan rate of 50 mV/s. They also have the lowest oxidation potential of CO. These excellent electrochemical performances are attributed to the uniform dispersion of PtNiCo nanoparticles, good conductivity, stability, and large specific surface area of the rGO carrier. The synthesized PtNiCo/rGO nanoparticles have an average size of 17.03 ± 1.93 nm. We also investigated the effect of catalyst material size on electrocatalytic performance, and the results indicate that PtNiCo/rGO NC catalysts can replace anode catalyst materials in fuel cell applications in the future.

Due to the depletion of fossil fuels, the demand for renewable energy has increased, thus stimulating the development of novel materials for energy conversion devices such as fuel cells. In this work, nickel nanoparticles loaded on reduced graphene oxide (Ni/rGO) with small size and good dispersibility were successfully prepared by controlling the pyrolysis temperature of the precursor at 450 °C, assisted by a microwave-assisted hydrothermal method, and exhibited enhanced electrocatalytic activity towards oxygen reduction reaction (ORR). Additionally, the electron enrichment on Ni NPs was due to charge transfer from the rGO support to metal nickel, as evidenced by both experimental and theoretical studies. Metal-support interactions between nickel and the rGO support also facilitated charge transfer, contributing to the enhanced ORR performance of the composite material. DFT calculations revealed that the first step (from O2 to HOO*) was the rate-determining step with an RDS energy barrier lower than that of the Pt(111), indicating favorable ORR kinetics. The HOO* intermediates can be transferred onto rGO by the solid-phase spillover effect, which reduces the chemical adsorption on the nickel surface, thereby allowing continuous regeneration of active nickel sites. The HO2- intermediates generated on the surface of rGO by 2e- reduction can also efficiently diffuse towards the nearby Ni surface or the interface of Ni/rGO, where they can be further rapidly reduced to OH-. This mechanism acts as the pseudo-four-electron path on the RRDE. Furthermore, Ni/rGO-450 demonstrated superior stability, methanol tolerance, and durability compared to a 20 wt% Pt/C catalyst, making it a cost-effective alternative to conventional noble metal ORR catalysts for fuel cells or metal-air batteries.

Preparation and catalytic behavior of reduced graphene oxide supported cobalt oxide hybrid nanocatalysts for CO oxidation