Developing efficient, durable, and earth-abundant electrocatalysts for both hydrogen and oxygen evolution reactions is important for realizing large-scale water splitting. Nanoparticle systems present unique advantages in terms of deposition method, scalability, and surface area. Furthermore, an incredible range in materials can be rapidly synthesized and screened. Our focus is in exploring novel materials for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), and understanding how the surface chemistry affects the catalytic process. We report that FeB2 nanoparticles, prepared by a facile chemical reduction of Fe2+ using LiBH4 in an organic solvent, are superb bifunctional electrocatalysts for overall water splitting. The FeB2 electrode delivers a current density of 10 mA/cm2 at overpotentials of 61 mV for the HER and 296 mV for the OER in alkaline electrolyte with Tafel slopes of 87.5 and 52.4 mV/dec, respectively. DFT calculations demonstrate that the boron-rich surface possesses an appropriate binding energy for chemisorption and desorption of hydrogen-containing intermediates, thus favoring the HER process. The excellent OER activity of FeB2 is ascribed to the formation of a FeOOH/FeB2 heterojunction during water oxidation. We will also discuss our efforts to improve the stability of CdSe colloidal quantum dots (CQD) when used for photoelectrocatalysis. To enhance the stability and performance, we employ a film structure composed of organic PEDOT:PSS acting as a hole transport layer, CdSe CQDs acting as a semiconducting light absorber, and conformal atomic layer deposition (ALD) Pt layer serving as both a passivation layer and cocatalyst for hydrogen evolution. The PEDOT:PSS/CdSe/Pt photocathode with 300 cycles of Pt ALD shows a high photocurrent density of -2.14 mA/cm2 at 0 V vs. RHE and high stability in acidic electrolyte.

Nanoparticle catalysis: Understanding the role of the surface and surface-passivation in creating stable, efficient and scalable devices

255th National Meeting (2018)

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