1. Department of Mechanical and Aerospace Engineering University of California, Irvine 5200 Engineering Hall Irvine CA 92617–2700 USA
2. Department of Mechanical Science and Engineering University of Illinois at Urbana‐Champaign Urbana IL 61801 USA
3. Department of Electrical and Computer Engineering University of Illinois at Urbana‐Champaign Urbana IL 61801 USA
4. Materials Research Laboratory University of Illinois at Urbana‐Champaign Urbana IL 61801 USA
5. International Institute for Carbon Neutral Energy Research (WPI‐12CNER) Kyushu University 744 Moto‐oka, Nishi‐ku Fukuoka 819‐0395 Japan