A novel composite CdS/meoporous zirconium titanium phosphate (ZTP) photocatalyst working under visible light was successfully prepared by a two-step thermal sulfidation procedure. The composite photocatalyst prepared by this method was found to show an activity superior to that of catalysts prepared by direct sulfidation either at room or high temperature. By choosing different Zr/Ti ratios, the conduction band of ZTP could be continuously adjusted. The optimal Zr/Ti ratio was found to be 1:3, where the energy difference between the conduction bands of CdS and ZTP can ensure a large driving force for fluent electron transfer from CdS to ZTP and the conduction band of ZTP substrate is still high enough for efficient hydrogen production. The quantum yield of this composite photocatalyst at 420 nm as measured in experiments reached 27.2%.

The design and fabrication of a gas-phase microreactor that is based upon a multilayer laminate microelectronics structure is described. The reactor is a key component in an integrated system whose platform utilizes a commercial computer chassis with modular boards to perform the required process functions. The design combines knowledge from earlier laminate microstructures with new prototyping concepts for incorporation of various on-board devices. A 3-D finite element simulation model was used to identify various design improvements. The final device contains two parallel reaction channels on a chiplike die in which a 1 μm platinum film catalyst is deposited on the underside of a silicon nitride membrane. Seven platinum heaters and temperature sensors are evenly distributed along the top side of the silicon nitride membrane. Electrical contacts for the on-board control and sensing devices are achieved through various pins that are distributed around the reactor die. The experience and knowledge gained in developing the final reactor device is utilized in Part 2 of this series for reactor packaging and development of the integrated system modules.

An integrated packaging system is developed for the multilayer laminate gas-phase microreactor die whose design and fabrication was described in Part 1 of this series. A commercial plastic socket used for integrated circuit testing was adapted so the reactor chip could be easily installed while maintaining consistent alignment with all electrical contacts. A heated fluidics interface was developed that connects the nonmetallic feed and product gas ports on the microreactor chip to metal tubing. Thermal experiments and 3-D finite-element heat transfer simulations of the combined socket-fluidics assembly showed that the plastic reactor socket could be safely operated up to 250°C. Other tests showed that the microreactor heaters were capable of achieving membrane temperatures in excess of 600°C.Step-response tests demonstrated that temperature changes of ca. 100°C could be achieved in less than 10 ms. Testing of the electrical leads on the reactor chip verified that the device resistance on a single reactor chip was uniform within a few percentage points. The packaged system developed here is used in Part 3 of this series to create a modular reactor board for incorporation into an integrated process system.