Capabilities

Capabilities

Surface Modifications for Catalysis and Corrosion Mitigation

Laboratory

National Renewable Energy Laboratory (NREL)

Capability Expert

Todd Deutsch; James Young; Katie Hurst

Class

Benchmarking
Characterization

Node Readiness Category

1: Low-Temperature Electrolysis (LTE)
1: Photoelectrochemical (PEC)

Description

This capability involves performing modifications to surfaces to overcome inherent poor stability or insufficient catalysis of either photoelectrochemical (PEC) or low-temperature electrolysis (LTE) materials. Prior to modification, the surface might require preparation, for example, by chemical or plasma etching. Several noble metal hydrogen evolution catalysts can be applied at very low loadings by sputtering, atomic layer deposition (ALD), or electrodeposition to improve the kinetics of the water reduction half-reaction, which can also enhance stability. We can also apply water oxidation catalysts (e.g., IrOx, RuO2) to either photoanodes or dark anodes to minimize the water oxidation overpotential and, thus, maximize solar-to-hydrogen (STH) efficiency. Low-energy nitrogen ion implantation can also be performed, which has contributed to enhancing the PEC stability of some III-V semiconductor systems. We also have the ability to apply thin films by ALD using a Beneq TFS 200 ALD reactor that is equipped with in situ quartz crystal microbalance (QCM) for chemical characterization of reaction gases. It has a complete toxic gas system that accommodates up to 12 sources at one time. The system supports growth for a wide range of pure materials, oxides, nitrides, sulfides, and selenides. The system is also equipped with plasma capabilities for additional functionalization and chemistry. The system is glove box integrated, enabling air-free transfer. An additional custom-built ALD reactor is available for more porous materials including powders. Thin oxide films have demonstrated protection of photocathodes and photoanodes and can also be used as an antireflective coating to maximize photon utilization efficiency. Another component of this capability is applying Ohmic contacts to semiconductors by e-beam evaporation or electrodeposition.

Capability Bounds‎

Some processing parameters, such as temperature for ALD or pH of electrodeposition bath, might be incompatible with some semiconductors. Sample dimensions are limited to the stage area of each technique. ALD deposition rates are approximately 10–50 nm/h and slower for high surface area substrates. In some cases, inhibited nucleation can delay or prevent deposition, which may be temperature dependent or require interlayer deposition. Two ALD systems are available to accommodate different sample configurations (i.e., powders and flat plate geometries). Some chemistries are not available on the custom-built ALD system.

Unique Aspects‎

This Fuel Cell Technologies Office-funded capability has been demonstrated to enhance stability for both PEC materials and fuel cell catalysts. The sputtering chamber has a rotating sample stage for uniform deposition. The shutter is pneumatically controlled and automatically timed. Rapid shutter actuation provides precise deposition times down to ~1 s duration, allowing very brief or "flash" depositions, such that low doses/loadings can be achieved. Another unique aspect is NREL's experience in processing multiple kinds of semiconductor materials and knowledge and expertise in application of Ohmic contacts. The ALD custom-built system is equipped with a rotating sample holder, and the Beneq system has a fluidized bed attachment to enhance the uniformity of coatings powders. The Beneq ALD system is attached to a glove box, providing air-less transfer of samples into and out of the reactor.

Availability‎

The capability currently exists, is functional and generally available for access. Throughput of some techniques, especially those performed in vacuum (ALD, ion implantation, sputtering) can be limited by stage size and pump-down time.

Benefit‎

This capability can provide catalysis and some protection from corrosion to improve STH efficiency and extend operational lifetimes. It may also enhance the performance and durability of the electrocatalysts, porous transport layers, or bipolar plates for electrolysis application. NREL and others have shown that N-ion implantation can enhance the stability of PtRu/C catalysts by affecting the catalyst-substrate interaction.

Images

Equipment for continuous or flash sputtering: a) vacuum chamber, b) sample stage, shutter, and sputtering source material target, c) plan view TEM of photoelectrode surface with resulting distribution of 2–5 nm PtRu particles (bright), and d) electrolyzer performance enhancement through Ir-coated Ti porous transport layers. The ALD capabilities include e) the Beneq reactor and f) the custom-built reactor.

References‎

  1. C. Liu, M. Carmo, G. Bender, A. Everwand, T. Lickert, J. L. Young, T. Smolinka, D. Stolten, W. Lehnert, "Performance Enhancement of PEM Electrolyzers through Iridium-coated Titanium Porous Transport Layers," Electrochemistry Communications (2018).
  2. J. Gu, Y. Yan, J. L. Young, K. X. Steirer, N. R. Neale, J. A. Turner, "Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst," Nature Materials 15 (2016): 456–460.
  3. Y. Yang, J. Gu, J. L. Young, E. M. Miller, J. A. Turner, N. R. Neale, and M. C. Beard, "Semiconductor interfacial carrier dynamics via photoinduced electric fields," Science 350 (2015): 1061–1065.
  4. A. A. Dameron, T. S. Olson, S. T. Christensen, J. E. Leisch, K. E. Hurst, S. Pylypenko, J. B. Bult, D. S. Ginley, R. P. O'Hayre, H. N. Dinh, and T. Gennett, "Pt-Ru Alloyed Fuel Cell Catalysts Sputtered from a Single Alloyed Target,"  ACS Catalysis 1 (2011): 1307–1315.
  5. https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/progress14/ii_d_1_deutsch_2014.pdf
  6. https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/progress13/ii_c_1_deutsch_2013.pdf
  7. J. L. Young, M. A. Steiner, H. Döscher, R. M. France, J. A. Turner, T. G. Deutsch, "Direct solar-to-hydrogen conversion via inverted metamorphic multijunction semiconductor architectures," Nature Energy 2 (2017): 17028.
  8. https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/review18/pd163_mi_2018_p.pdf?Status=Master
  9. A. Settle et al., "Enhanced catalyst durability for biobased adipic acid production by atomic layer deposition: toward scaled application," Joule, accepted (2019).