Session U5: Energy Research

Influence of water on the reaction path of the oxygen reduction reaction in fuel cells

The development of fuel cell technology has been limited in part due to the cost of the catalyst used in the cell and the rate limiting oxygen reduction reaction. We will present a molecular modelling study focus toward the prediction of improved durability and catalytic efficiency of the Platinum catalyst using doped graphene and doped single walled carbon nanotube surface. The most promising carbon supports - active centre systems were then studied in the gas phase and with explicit water molecules to model the oxygen reduction reaction and tailor the catalytic centres to improve the efficiency of this reaction while reducing the probability of occurrence of side reactions. Two major conclusions have been drawn from this analysis of the oxygen reduction reaction with and without water present. The doping of the carbon surface leads to a stronger platinum-surface interaction and does help the breaking of the oxygen-oxygen bond. These two are interrelated since the stronger surface-platinum bond allows for the same orbitals to interact with the oxygen-oxygen orbital. In addition, the dopants could make the surfaces more polar thus retaining water which might help catalyze the reaction, this property could be very promising to increase the effectiveness of fuel cell cathodes.   

Mono-layer BC$_2$ a high capacity anode material for Li-ion batteries

Mono-layer of graphene with high surface area compared to the bulk graphite phase, shows less Li uptake. The Li activity or kinetics can be modified via defects and/or substitutional doping. Boron and Nitrogen are the best known dopants for carbonaceous anode materials. In particular, boron doped graphene shows higher capacity and better Li adsorption compared to Nitrogen doped graphene. Here, using first principles density functional theory calculations, we study the spectrum of boron carbide (BC$_x$) mono-layer phases in order to estimate the maximum gravimetric capacity that can be achieved by substitutional doping in graphene. Our results show that uniformly boron doped BC$_2$ phase shows a high capacity of ? 1400 mAh/g, much higher than previously reported capacity of BC$_3$.   

Two orders of magnitude enhancement in Li diffusivity in FCC fullerene under pressure

Silicon having high specific capacity of 4200 mAh/g is a potential candidate for anode material in Li ion battery. However, it goes through huge volume change during lithiation and de-lithiation which breaks the electrical contacts. To protect Si anode, carbon based materials have been used experimentally as an artificial solid electrolyte interface (SEI). In order to find a good artificial SEI, Li kinetics also has to be very efficient in it. Here, we theoretically investigated Li kinetics in bulk FCC fullerene and polymerized fullerene modeled by applying hydrostatic pressure. We find that Li diffusion barrier decrease with increasing pressure upto 17.7\% volume strain, leading to two orders of magnitude gain in diffusivity compared to the unstrained case. This lowering of barrier can be attributed to the charge transfer triggered by strong interaction between fullerene and Li. Further enhancement of pressure leads to inter-fullerene bond formation that makes Li diffusion barrier high.   

Surface nanocrystalline and hardening effects of Ti--Al--V alloy by electropulsing ultrasonic shock

The effect of electropulsing ultrasonic shock (EUS) on the surface hardening and microstructure of Ti6Al4V alloy was studied. It was found that electropulsing improved the microhardness dramatically both in the influential depth and maximum value, compared with the only ultrasonic-shocked sample. It's indicated that refined surface layer with nanocrystalline and improved microhardness were obtained on account of surface severe plastic deformation, dynamic recrystallization (DRX) and phase change, which was implemented at relative low temperature and high strain rate/capacity due to the coupling of the thermal and athermal effects of EUS. It's different from conventional experiments and theory. It's discussed that the positive contributions of EPT in the thermodynamics and kinetics of microstructure and properties change were attributed to the reduction of nucleation energy barrier and acceleration of atomic diffusion. Therefore, it's supposed that EUS is an energy-saving and high-efficiency method of surface treatment technique with the help of high-energy electropulses, which is promising in cost reduction of the surface engineering and energy management.   

The Greatest Challenge Ever for Mankind, Requiring Policies of Accelerating Hardship and Implementation Difficulty

Providing energy for the contemporary world has resulted in a multi-variable problem in which a confluence of historical anomalies and economic, psychological, political, and demographic factors thwart efforts to prevent significant harm from increasing atmospheric CO2. This unlikely combination has created the perfect storm in which the warnings by scientists are ineffective. Global warming is occurring simultaneously with increased population, some dysfunctional political institutions, ascendency of oversimplified economic theory, campaigns to discredit scientists, misinterpretation of the meaning of noise in the Milankovitch climate cycles, and substantially improved hydrocarbon extraction methods. These factors are compounded by traits of human nature, such as greed and resistance to changing the familiar and discontinuing profitable endeavors. The idea that future people are equal with us may not be widely supported, yet this value is the foundation of climate change action. History shows that most people and nations will not take appropriate measures until forced, yet the cost increases as action is delayed. This makes appropriate policies even more extreme and difficult to accomplish as more wealth is consumed in treating global warming symptoms.