Investigation of fuel cell behavior with different catalyst loadings at varying humidities and temperatures

Proton exchange membrane fuel cells (PEMFCs) suffer from severe performance losses under low-humidity conditions, which limits their deployment in portable and open-cathode systems without external humidifiers. In this study, we systematically investigate the combined effects of platinum (Pt) loading (0.2–1.0 mg Pt cm −2 ), ionomer-to-carbon (I/C) ratio (0.6 and 0.8), and operating conditions (0–100 % RH, 40–70 °C) using commercial catalyst materials. We find that performance does not peak at full humidification but instead at intermediate RH values (50–75 %), with the optimum shifting lower as Pt loading increases. An intermediate loading (0.4 mg Pt cm −2 ) maximizes performance by balancing ORR kinetics, proton resistance, and water management. Increasing I/C ratio to 0.8 impairs performance under high humidity but substantially improves both water retention and durability under dry conditions by slowing electrochemically active surface area loss. These results establish clear design principles linking catalyst layer composition to operating environment, providing guidelines for reliable PEMFC operation in practical low-humidity applications such as UAVs and portable devices. • Systematic study of catalyst loading and ionomer/carbon ratio in PEMFCs. • Loading of 0.4 mg Pt cm −2 balances kinetics, proton resistance, and water management. • Peak performance shifts from 75 % RH (low loadings) to 50 % RH (high loadings). • Higher I/C ratio (0.8) enhances durability and water retention under dry operation. • Results provide design rules for reliable PEMFCs in low-humidity, portable applications.