TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The vehicle is selected from water, methanol, ethanol, propanol, 1-propanol, 2-propanol, glycols, ethylene glycols, and/or propylene glycol; and it comprises water water (preferably in an amount of greater than 60 wt.%). The catalyst particles comprises at least one of an elemental metal or an alloy (preferably platinum or an alloy of platinum and ruthenium); and supported catalyst particles.    TECHNOLOGY FOCUS - POLYMERS - Preferred Ink: The ink comprises the polymer electrolyte ionomer in an amount of 0.5-5 wt.%. Preferred Method: The depositing involves spraying; and the vaporizing includes heating the membrane. The process involves controlling catalyst layer porosity by controlling the temperature of the membrane. The process further involves e) controlling porosity in the multiple stacked catalyst layers by controlling the amount of vehicle vaporized in each alternating vaporizing step. In the process, the amount of vehicle vaporized in each alternating vaporizing step increases so as to create a porosity gradient in a direction perpendicular to a surface of the membrane. The steps (c) and (d) are alternated at least five times. The spraying involves aerosolizing the ink into several catalyst-containing droplets having an average droplet size of 20-60 microns. The multiple stacked catalyst layers are formed on the membrane through alternating spraying and vaporizing steps. The spraying involves i) spraying a first portion of the membrane with a first ink mixture comprising the liquid vehicle, a first catalyst amount of catalyst particles, and a first polymer electrolyte ionomer amount of polymer electrolyte ionomer; and ii) spraying a second portion of the membrane with a second ink mixture comprising the liquid vehicle, a second catalyst amount of catalyst particles, and a second polymer electrolyte ionomer amount of polymer electrolyte ionomer, under conditions to form a catalyst gradient and/or polymer electrolyte ionomer gradient on the membrane. The process forms a catalyst layer having a vertical gradient. The process is repeated, optionally with a second ink, for the other side of the membrane. The step (j) is repeated in several passes to form multiple stacked catalyst layers. Preferred Components: The weight ratio of the catalyst particles to the polymer electrolyte ionomer is greater than 5:1; and at least a majority of the catalyst particles have a spherical morphology. The catalyst particles have an average particle size of 1-10 microns; or 200-1000 nm. The catalyst particles comprises metal crystallites having an average crystallite size of less than 10 nm. The weight ratio of the catalyst particles to the polymer electrolyte ionomer in the ink is 2-10. The catalyst particles comprises a mixture of at least two different types of catalyst particles. The polymer electrolyte ionomer comprises a sulfonated tetrafluoroethylene copolymer. The membrane comprises a heated membrane (preferably a polymer electrolyte membrane). The multiple stacked catalyst layers are formed on the membrane through alternating spraying and vaporizing steps, the multiple layers being formed from multiple inks, at least two of the multiple inks, respectively, comprises catalyst particles having different average particle sizes from one another; or comprises compositionally different catalyst particles from one another. The gradient comprises a horizontal gradient or vertical gradient. The vertical or horizontal gradient comprises a vertical porosity gradient, a particle size gradient, or a catalyst particle concentration gradient. The polymer electrolyte membrane further comprises a second surface; and the catalyst coated membrane further comprises a second catalyst layer disposed on the second surface. The first catalyst layer comprises polymer electrolyte ionomer and catalyst particles. EXAMPLE - Deionized water (8 g) was added to platinum/ruthenium black catalyst particles (1 g). The mixture was horn sonicated in ice at duty cycle 50 amplitude 20% for 10 minutes (750 W, using 20% of maximum power). Nafion (RTM:perfluorinated ion exchange resin solution) (3.53 g) containing EW1100 (RTM: lower aliphatic alcohol/water (20%) solution containing 2-propanol, 1-propanol and methanol)) was added to the mixture. The final mixture was again horn sonicated in ice, duty cycle 50 amplitude 20% for 5 minutes (750 W, using 20% of maximum power) to give an anode ink. The ink stability and viscosity were measured. The ink showed a viscosity: stability of 12.60 cP: 1 hr.