(594b) Improving Precision in Materials Synthesis for Hydrogen Electrocatalysis

Our research group is broadly interested in the synthesis and characterization of nanoparticulate catalysts for electrochemical energy conversion in aqueous alkaline electrolytes. Our primary focus to date has been on nonprecious catalysts for hydrogen evolution/oxidation in the long-term pursuit of efficient renewable energy storage via alkaline unitized regenerative fuel cells. This field has gained increased interest recently due to the attractiveness of alkaline operating conditions for capital cost reductions and the emerging availability of high-performing oxygen evolution/reduction catalysts and alkaline anion exchange membranes. By contrast, work on alkaline hydrogen electrochemistry has been hindered by two research challenges. The first is the lack of consensus regarding materials and methods for reproducible controls against which new catalysts can be evaluated. The second is the difficulty of making “apples-to-apples" comparisons between novel catalyst candidates that exhibit widely different morphologies. This presentation will describe our recent work to address each of these challenges by deploying precise synthetic methods for nanocatalysts.

To address the challenge of enabling high-quality controls in hydrogen electrochemistry, we have developed a straightforward method for generating clean Pt nanoparticles. The approach is based on a simple thermal reaction between a Pt(IV) precursor and ascorbic acid in the presence of sodium polyacrylate as a solubilizing agent. The resulting polycrystalline nanoparticles are uniform and 3-4 nm in size which can be readily recovered and cleaned using an aqueous base treatment. They can be directly deposited on any substrate of interest with or without a catalyst support, and they demonstrate consistently high activity toward hydrogen evolution/oxidation in acid and alkaline electrolytes.

In the interest of facilitating direct comparisons between candidate hydrogen evolution/oxidation electrocatalysts, we are leveraging a versatile method for synthesizing metal composite nanoparticles that involves the use of extremely powerful reducing agents in nonaqueous solution. This method enables us to generate uniform nanoparticles comprising mixtures of nearly any mixture of transition metals. We are also developing a unique technique adapted from the semiconductor nanofabrication literature to synthesize polycrystalline thin films whose surface roughness is on the order of a single bond length. This degree of dimensional control is expected to enable new insights into electrocatalyst structural evolution under operating conditions.