Size‐Selective Photoelectrochemical Reactions in Microporous Environments: Clark Probe Investigation of Pt@g‐C₃N₄ Embedded into Intrinsically Microporous Polymer (PIM‐1)

Abstract

Graphitic carbon nitride (g‐C3N4) with photo‐attached platinum (Pt@g‐C3N4) is known to generate hydrogen under illumination in aqueous environments in the presence of carbohydrate hole quenchers. Here, Pt@g‐C3N4 is embedded into a polymer of intrinsic microporosity (PIM‐1) host material with a molecularly rigid structure to maintain active unblocked catalyst surfaces and to control transport to/from the photocatalyst. A Clark‐type oxygen/hydrogen sensor is employed with Pt@g‐C3N4 embedded into PIM‐1 applied as a film to be the gas‐permeable sensor membrane. Oxygen reduction and hydrogen production are observed in situ as a function of light exposure and quencher concentration. Significant size‐selectivity favouring smaller more flexible saccharides or carbohydrate/ hydrocarbon quenchers is observed and attributed to rate limiting PIM‐1 micropore transport. Effective hydrogen production through a Teflon membrane is demonstrated. The underlying hydrogen production/ photocurrent enhancing effects of the microporous PIM‐1 film on the photochemical process are revealed.

Hydrogen Peroxide Versus Hydrogen Generation at Bipolar Pd/Au Nano-catalysts Grown into an Intrinsically Microporous Polyamine (PIM-EA-TB)

“…Without addition of formic acid, the Clark probe (at − 0.7 V vs. Ag/AgCl) equilibrates to about − 0.35 µA after 5 min. This corresponds to the oxygen flux from solution through the Nylon disk, through the sensor film, and to the underlying platinum sensor electrode consistent with previous reports [33]. The equilibration time (the time to quasi steady state) of 2 to 5 min is typical, although slower equilibration may be anticipated in the case of additional catalytic reactions at the coated Nylon disk.…”

“…8C) as a function of formic acid, a "switch-on" transition occurs at approximately 10 mM formic acid with more formic acid leading to a plateau in the response probably linked to saturation of the solution with hydrogen. The Clark probe current (with + 0.6 V vs. Ag/AgCl applied voltage) for high formic acid concentrations is consistent with the response expected when intentionally bubbling hydrogen gas to saturate the solution [33]. When purging the solution with argon gas and then adding formic acid, very similar Clark probe responses are recorded (see Fig.…”

“…These "guest" nanoparticles are active for hydrogen generation from formic acid due to PIM-EA-TB not blocking the surface of the catalyst and effective permeation of formic acid. Both hydrogen production and oxygen consumption are monitored in situ with a Clark probe [33] (Fig. 1A) and employing Nylon mesh substrates.…”

Effects of g-C3N4 Heterogenization into Intrinsically Microporous Polymers on the Photocatalytic Generation of Hydrogen Peroxide

“…Both PIM-1 and PIM-EA-TB have been employed previously for embedding catalysts with the aim of minimizing catalyst surface blocking by avoiding detrimental PIM-catalyst interactions (due to molecular rigidity in the polymer backbone) and maximizing catalyst performance (due to a fully accessible catalyst surface). We have recently demonstrated photocatalytic hydrogen production with a co-catalyst-modified g-C 3 N 4 embedded into a PIM …”

TiO2 nanocrystal rods on titanium microwires: growth, vacuum annealing, and photoelectrochemical oxygen evolution

“…Further investigation is possible with a photo-Clark probe approach. 32 Fig. 8A illustrates the approach with a Clark probe as an oxygen sensor exposed to blue LED light.…”