The GAO Materials Chemistry Research Group

Today is Geoff’s 79th birthday. Besides celebrating it online with family, friends, colleagues and alumni on the topic of “ride the train, save the world”, a birthday paper entitled “Accelerated optochemical engineering solutions to CO2 photocatalysis for a sustainable future” has been online today. In this perspective, Geoff systematically looked at the past and present of the gas-phase heterogeneous CO2 photocatalysis by introduction of the background and summary on the state-of-the-arts.

Geoff points out that the vision of CO2 photocatalysis is to produce a pyramid of fundamental chemicals from CO2 and H2O to counter the climate change as illustrated in above picture, and currently, there are four main directions in seeking for high solar-to-chemical energy efficiency: 1) Materials engineering strategies and new reactor designs for enhanced-performance heterogeneous CO2 photocatalysis; 2) Computational modeling of design strategies for studying light and heat transport in photocatalytic CO2 hydrogenation processes; 3) Comparison of thermochemical, photochemical, and photothermal CO2 utilization strategies and future opportunities; 4) Determining key technoeconomic decision-making criteria for assessing photocatalytic process viability and potential the cost of a mole of photons to generate a mole of product is a pivotal metric to decide whether or not the industrialization of CO2 photocatalysis is technologically and economically viable.

Based on this, Geoff proposes that the accelerated development of the CO2 photocatalysis is necessary given the looming climate change. The vision is based on revolutionary scientific advances of self-driving laboratories that are expected to creatively integrate artificial intelligence, machine learning, robotic automation, and data management tools to accelerate the discovery of high-efficiency photocatalysts and photoreactors through fast, low-cost, and parallel rather than slow and expensive serial procedures. See full story at Matter.

Direct air capture technology removes carbon dioxide from the air and compresses it for sequestration or utilization and promises to help us meet net-zero emissions goals. However, the process of direct air capture can be energy and land intensive and expensive. To design a direct air capture process that uses less energy and less land, a multi-disciplinary team outlines a plan to retrofit train cars to remove carbon from the air at a much lower than average cost per tonne in an article published in a peer-reviewed article in the journal Joule on July 20.

Stationary direct air capture facilities require large areas of land to house their equipment and construct the renewable energy sources required to support them. Obtaining the proper permits to operate can be difficult, and many residents are opposed to the construction of these large facilities in their towns and cities. “It’s a huge problem because most everybody wants to fix the climate crisis, but nobody wants to do it in their backyard,” says co-author Geoffrey Ozin, a carbon dioxide utilization chemist and chemical engineer and director of the solar fuels group at the University of Toronto. “Rail-based direct air capture cars would not require zoning or building permits and would be transient and generally unseen by the public.”

These purpose-built train cars use large vents to intake air, which would eliminate the need for the energy-intensive fan systems that stationary direct air capture systems use. After a sufficient amount of carbon dioxide has been captured, the chamber is closed, and the harvested carbon dioxide is collected, concentrated, and stored in a liquid reservoir until it can be emptied from the train at crew-change or fueling stops for direct transportation into the circular carbon economy or to nearby geological sequestration sites. The carbon-dioxide-free air then travels out the back or underside of the car and returns into the atmosphere.

When a train pumps the brakes, its energy braking system converts forward momentum into electrical energy. As the braking system is applied, the energy is dissipated in the form of heat and discharged out of the top of the train. “That is wasted energy,” says lead author E. Bachman, founder of CO2Rail. “Every complete braking maneuver generates enough energy to power 20 average homes for a day, so we’re not talking about a trivial amount of energy.” This energy, the authors suggest, should be used to help mitigate climate change.

The authors argue that direct air capture becomes an even more viable climate solution because the rail system is already in place. “The infrastructure exists,” says Ozin. “That’s the bottom line. All you need to do is take advantage of what is already available.”

The researchers say that an average freight train with these direct air capture cars could remove up to 6,000 tonnes of carbon dioxide per year. Because its sustainable-energy needs are being supplied by on-board sources, the price per tonne is significantly lower than that of other direct air capture systems. “The projected cost at scale is less than $50 per tonne, which makes the technology not only commercially feasible but commercially attractive,” Bachman says.

The authors hope this technology could have a positive impact beyond the carbon it removes from the atmosphere. “We could get a positive-feedback loop where the encouragement of rail to broadly deploy these direct air capture rail cars could even further decrease carbon emissions because rail is about five or six times more efficient than trucks,” says Bachman. “By increasing rail utilization, you increase the efficiency of the entire transportation system.” See full story at Joule.

Have you ever wondered how much solar heat is stored in the deserts of the world and wasted. Imagine if it could be utilized! We all know under the threat of climate change that cost-effective energy storage solutions is a world-wide objective to enable the transition from fossil to renewable forms of energy. Different storage media have been discovered so far such as gravity, lithium-ion batteries, supercapacitors, and molten salts. Recently, a Finnish start-up company Polar Night Energy demonstrated the potential of ultra-cheap sand for energy storage, which is totally green with reported power up to 100 MW, capacity up to 20 GWh, and efficiency as high as 99%. While it sounds like too good to be true, the core idea is to use solar or wind electricity to heat sand to 600-1000 °C and reuse the thermal energy to heat buildings or regenerate electricity. Then here goes one of the most fascinating points—the thermal energy can be stored for months before it degrades. Furthermore, the infrastructure of the sand system is straightforward, sands and pipes in cylinders at smaller scales or sands and pipes in canyons at larger scales, with vacuum containment for insulation. Due to abovementioned merits, the Polar Night Energy already is working to build energy storage facilities world-wide. See full story at Advanced Science News.

CO2-to-methanol catalysis is an appealing way for the production of solar fuels. The benchmark catalyst is the decades-old Cu/ZnO/Al2O3 that demonstrates high stability and high activity, but it should be operated under high hydrogen concentration (>75%) and high pressure to suppress the competing reverse water-gas shift side-reaction (CO2-to-CO). In a recent work, Lu, Chengliang, and Geoff showcased a black In2O3-x(OH)y catalyst that can shift the competing CO and methanol production to cooperative one. To amplify, the hydridic In-H and protonic In-OH in the catalyst forms surface frustrated Lewis pair (SFLP) to enable facile CO2 activation to CO, with the SFLP degraded to oxygen vacancy. Fortunately, the produced CO can be captured by the oxygen vacancy and be transformed into methanol on site. After the desorption of methanol, the oxygen vacancy is recycled to SFLP upon H2 heterolysis. As a result, the methanol synthesis over In2O3-x(OH)y is promoted by the CO formation, surpassing the Cu/ZnO/Al2O3 catalyst under ambient pressure and 50% H2 concentration. See full story at Nature Communications.

Besides acting as the most widely used semiconductor materials, silicon in oxide form (silica SiO2) has attracted broad interests in environmental and energy catalysis recently due to the low cost, non-toxicity and ubiquitous presence in the Earth’s crust. In this Review of silica mediated catalysis, Wei and co-authors begin by brief discussions of the general applications of silica, methods to engineer it, and the mechanistic understanding during catalysis processes. This is followed by a discussion of some recent examples that silica counterintuitively goes beyond the general understandings, including interplay with optics/thermal conduction to enhance photocatalysis and geometric confinement of supported metals to show strong metal-silica support interaction. Throughout the Review the authors attempt to highlight the novel and emerging designs that broaden the limits of silica. See full story at Chem Catalysis.

Catalyst stability is the most important parameter for industrial application. For example, Cu is a prestigious CO2 catalyst, but its durability is partially limited by the sintering of Cu nanoparticles under high temperature. Increasing the Cu-support interaction can enhance stability, which is typically realized on reducible metal oxides via in-situ migration to partial Cu coverage. In a recent work, Wei and Geoff developed an alternative method to expand the strong metal-support interaction to non-reducible silica supported Cu. Within the novel design, a two-dimensional multi-layer SiO2 support is prepared by topological exfoliation of CaSi2 with CuCl2 and thereafter calcination Cu nanoparticles, and thus Cu nanoparticles are encapsulated and confined between layers. The prepared Cu-SiO2 catalysts exhibit excellent activity and long-term stability in high-temperature CO2 hydrogenation reactions. See full story at Advanced Science.

Chemical industry is a stubborn sector for decarbonization but the benefits could be enormous. To cut the emission of chemical industry, current solution is electrification of which the power is supplied by grid electricity, while the long-term goal is to develop pure renewable energy-driven carbon-neutral or carbon-negative techniques. To this regard, photocatalysis is among the most appealing pathways. In a recent study in ACS Energy Letter, the economic viability of photocatalytic chemical production is found to be promoted by reduced cost of renewable energy and enhanced efficiency of LED. See full story at Advanced Science News.

A global energy transition is expected to increase the share of renewable energy from current 12% to 90% in 2050. Different from the on-demand fossil fuel, inteminent renewable energy including solar and wind calls for large-scale, cost-effective grid-scale energy storage facilities. Currently, the energy storage is dominated by gravity-based pumped hydro (90%), followed by lithium, lead and zinc batteries (5%), and then the rest. Recently, a Swiss company Energy Vault demonstrated potential to change this framework by the use of cranes to lift and lower heavy composite blocks into massive architectures, which delivers gigawatts capacity and remarkable energy efficiency of 83-85%. See full story at Advanced Science News.

The war in Ukraine has araised the global concern for possible chip shortage due to disruption in semiconductor-level neon supply. Being the world’s major neon supplier, Ukraine perfects the process of concentrating 18 ppm neon in air to 99.999% purity based on cryogenic fractionation. This kind of high-purity neon is used to trigger the 193 nm-deep ultraviolet wavelength for the state-of-the-art 7 nm spatial resolution photolithography, together with argon and fluorine in an excimer laser. The excited-state chemistry behind the argon-fluorine-neon excimer laser is explained in detail by Geoff, as well as why the neon is necessary during the process. See full story at Advanced Science News.

It is with great delight and excitement to announce that Professor Geoffrey Ozin is the 2022 Killam Prize winner for his leading work in nanoscience. The Killam Prizes are awarded by the Canada Council for the Arts and among Canada’s most prestigious prizes for careers in research, which is to “recognize and celebrate our most inspiring scholars and thought leaders.” Five awards are given, one each in the fields of humanities, social sciences, natural sciences, health sciences, and engineering. Each of the Laureates receive $100,000 in award funding.