Carbon neutrality has been the most popular topic of the twenty-first century. Substitutingnon-sustainable fossil fuels with the cleaner energy source hydrogen is a viable strategy for reducing total carbon footprints, but the conventional method of hydrogen production is energy-intensive and polluting. Water electrolysis stands out among all hydrogen production methods due to its low instrumentation requirements and high efficiency. However, water electrolysis costs have yet to be reduced. By engineering the catalysts used at the cathode and anode, the focus of this thesis will be to improve the water electrolysis efficiency and material durability. In addition, corresponding theory is studied in order to reveal the structureperformance relationship of the catalyst, which provides perspective and theoretical support for the design of future catalysts.

In the first chapter, I will briefly describe the current status of global carbon production.The rationale for selecting water electrolysis is then presented, along with an overview of water electrolysis devices.

In the second chapter, I will describe our work (J. Am. Chem. Soc. 2018, 140, 29, 9046–9050) on improving the performance of the hydrogen evolution reaction (HER) by applyingsurface engineering to PtNi alloy. Hydrogen holds the potential of replacing nonrenewable fossil fuel. Improving the efficiency of hydrogen evolution reaction (HER) is critical for environmental friendly hydrogen generation through electrochemical or photoelectrochemical water splitting. Here we report the surface-engineered PtNi-O nanoparticles with enriched NiO/PtNi interface on surface. Notably, PtNi-O/C showed a mass activity of 7.23 mA/μg at an overpotential of 70 mV, which is 7.9 times higher compared to that of the commercial Pt/C, representing the highest reported mass activity for HER in alkaline conditions. The HER overpotential can be lowered to 39.8 mV at 10 mA/cm2 when platinum loading was only 5.1 μgPt/cm2, showing exceptional HER efficiency. The performance improvement could be attributed to the successful creation of Ni(OH)2/Pt(111) interface. Ni(OH)2 facilitated H2O molecule to be adsorbed on the surface as the first step of HER, and then recombination on the Pt(111) surface happened. Thus, the overall potential needed was decreased. Meanwhile, the prepared PtNi-O/C nanostructures demonstrated significantly improved stability as well as high current performance which are well over those of the commercial Pt/C and demonstrated capability of scaled hydrogen generation.

In the third chapter, I will demonstrate continuation of the last work, which is furtherimproving the alkaline HER performance on Pt-based alloy. Lattice tuning is one of the effective ways to optimize the HER performance on Pt-based alloy. Here, we report a facile lattice tuning method on Pt-based alloy using Cu addition to control the lattice parameter for optimal HER performacne. During the performance evaluation, PtCuNi/C and PtCuNi- O/C showed an average overpotential of 38.8 mV and 31.3 mV at 10 mA/cm2, respectively. The overpotential of PtCuNi-O/C is dramatically smaller than that of commercial Pt/C (115.2 mV). At an overpotential of 70 mV (-70 mV vs. RHE), the octahedral PtCuNi/C presents a mass activity (MA) of 4.9 mA/μgPt, while the PtCuNi-O/C demonstrates a MA of 8.7 mA/μgPt, which is nearly 9.5 folds to that of the commercial Pt/C (0.92 mA/μgPt). Also, the PtCuNi-O/C can reach a current density of 114 mA/cm2 at -0.2 V vs. RHE without iR compensation, which is well above that of Pt/C (22.4 mA/cm2), indicating a promising potential for the industrial scale hydrogen production. For the stability test, in contrast to the 160.1 mV potential drop for the Pt/C, there was only 55.5 mV, 48.2 mV potential drop for octahedral PtCuNi/C, PtCuNi-O/C, correspondingly, showing a significantly improved durability. Moreover, the dealloyed nanocatalysts showed the best performance when the lattice parameter is in the range of 0.3825-0.3835 nm for both PtNi-O/C and PtCuNi-O/C. In the fourth chapter, the main focus will be on the anode side featuring oxygen evolution reaction (OER) in acidic media. Developing durable non-precious catalysts for the acidic OER is crucial for the hydrogen production industry. In this regard, we report a facile strategy to synthesize the cobalt-based spinel oxide for the acidic OER with ultrahigh activity and outstanding durability. Specifically, the as-prepared NiCo2O4 delivered a low overpotential of 407 mV vs. reversible hydrogen electrode at 100 mA/cm2 and only a 68.9 mV increase at 10 mA/cm2 after 20 hours of chronopotentiometry test. Ex situ x-ray absorption spectroscopy studies revealed that Ni mainly occupies the octahedral site. In situ x-ray absorption spectroscopy studies demonstrated that adding Ni helped minimize the structure change during the OER, leading to NiCo2O4’s outstanding durability. Density functional theory calculations demonstrated that the OER overpotential is lowered by 90 mV on the NiCo2O4 surface compared to that of Co3O4. The acidic OER on the NiCo2O4 spinel structure undergoes a kinetically more favorable direct O-O coupling mechanism rather than the adsorbate evolution mechanism, which was seldom reported regarding acidic OER on non-precious metal oxides. We showcase an ideal way to produce cobalt-based spinel oxides following direct O-O coupling mechanism design rules, achieving promising acidic OER performance cost-effectively.

The last chapter generally conclude the content covered in the thesis and provided someperspective on future catalyst design and scale-up applications.

In 2012, over 25% of the bridges in the United States were rated as structurally deficient or functionally obsolete. Moreover, 35% of bridges are serving beyond their theoretical design lifespan and the number has been projected to increase over the next decade. The imperative needs of improving the overall condition of the bridge system has been impeded by the shortage of funding available for bridge repairs and maintenance. In 2006 the gap between Federal Highway Administration's (FHWA) estimates to eliminate the bridge maintenance backlog and the actual appropriations to bridges for repairs and maintenance from the Highway Bridge Program was $43.4 Billion. In 2009, the gap increased to $65.7 Billion. Such conflict has made effective bridge management more critical than ever.

In bridge management, agencies collect bridge condition data and develop deterioration models that predict the bridges' future conditions and associated costs, based on which maintenance, rehabilitation and reconstruction (MR&R) decisions are made. It is therefore critical to have accurate deterioration models. However, limited availability of data and incomplete understanding of the deterioration process result in inaccurate models, which lead to sub-optimal MR&R decisions and significant cost increases.

To address the inaccuracy stemming from limited bridge condition data, researchers have proposed Adaptive Control (AC) methods that update the deterioration models successively as new data become available. The underlying belief is that agencies can obtain more accurate deterioration models through updating and subsequently improve their MR&R decisions and achieve cost savings. State-of-the-art bridge management systems, such as Pontis, use a class of AC procedures known as Certainty Equivalent Control (CEC). The procedure used in Pontis updates the transition probabilities (i.e., the parameters of the component deterioration models) after each condition survey, and uses the updated probabilities in subsequent planning of MR&R decisions. Unfortunately, CEC does not necessarily lead to more accurate models, or guarantee savings in system costs; in other words, updating of the type in Pontis is not necessarily beneficial.

In the present dissertation, an AC method, Open-Loop Feedback Control (OLFC), is proposed for system-level bridge management. The performance of OLFC and the Pontis CEC is tested in a numerical study and empirical results show that OLFC has superior performance with respect to two criteria. In terms of improvement in model accuracy, the Pontis CEC yields systematic bias in model parameter estimates and therefore does not improve model accuracy. In all testing scenarios, the resulting deterioration models lead to faster deterioration than the true models. OLFC, on the other hand, results in consistent convergence to the true models in all testing scenarios and improves model accuracy. When evaluated by system costs, the Pontis CEC consistently results in higher system costs than the no-updating scenario. The increases are on the order of $180 Million at the level of the State of California. To the contrary, updating with OLFC consistently achieves system costs savings compared to the no-updating scenario, and results in system costs that do not differ significantly from the system costs when true models are used for MR&R decision-making.

In addition, a computationally tractable optimization routine is developed for MR&R decision-making. The routine ensures strict conformity to system budget constraints and achieves satisfactory computational efficiency even given high levels of heterogeneity in bridge systems.