Energy consumption is currently over-reliant on non-renewable energy sources. One promising pathway towards a renewable future is the solar thermochemical process that can be used to produce hydrogen via water splitting. Current solar thermochemical reactors utilize CeO2 as the nonstoichiometric material for the two-step redox process; however, the high reaction temperatures required have opened the opportunity for using new compounds with favorable thermodynamic and kinetic properties, such as perovskites. The cycle efficiency can be further improved by using ceramic foams with macroporous structures due to their enhanced heat transfer properties compared to powder and monoliths. We have recently shown that porous lanthanum strontium manganite (LSM) can produce a 3 times greater hydrogen yield compared to CeO2 during isothermal H2 production. Now, using computational methods to expand our material search, we have identified B-site doped LSM compositions with oxygen vacancy formation energy values between 2.5 and 5 eV and have analyzed their nonstoichiometry via thermogravimetric analysis. Specifically, we have compared LSM to LSM doped with Al (LSMA) and Ga (LSMG). We investigate the effect of microstructural features (pore size, grain size, and overall porosity) on the kinetics and yield during isothermal H2 production and the comparative performance of LSM vs. LSMA vs. LSMG powders, pellets, and foams.