Amphiphilic Ti porous transport layer for highly effective PEM unitized regenerative fuel cells
Ahyoun Lim, Hui‐Yun Jeong, Youngjoon Lim, Jin Young Kim, Jin Young Kim, Hee‐Young Park, Hee‐Young Park, Jong Hyun Jang, Yung‐Eun Sung, Jong Min Kim, Jong Min Kim, Hyun S. Park, Hyun S. Park
Abstract
Polymer electrolyte membrane unitized regenerative fuel cells (PEM-URFCs) require bifunctional porous transport layers (PTLs) to play contradictory roles in a single unitized system: hydrophobicity for water drainage in the fuel cell (FC) mode and hydrophilicity for water supplement in the electrolysis cell (EC) mode. Here, we report a high-performance amphiphilic Ti PTL suitable for both FC and EC modes, thanks to alternating hydrophobic and hydrophilic channels. To fabricate the amphiphilic PTL, we used a shadow mask patterning process using ultrathin polydimethylsiloxane (PDMS) brush as a hydrophobic surface modifier, which can change the Ti PTL's surface polarity without decreasing its electrical conductivity. Consequently, performance improved by 4.3 times in FC (@ 0.6 V) and 1.9 times in EC (@ 1.8 V) from amphiphilic PTL. To elucidate reason for performance enhancement, discrete gas emission through the hydrophobic channels in amphiphilic PTL was verified under scanning electrochemical microscopy.