From Science Daily:
Mimicking photosynthesis, water-splitting cells absorb sunlight and produce fuel. A challenge in designing such cells is pairing the semiconductor that absorbs sunlight and generates electrons with the catalyst that uses those electrons to produce fuel. Researchers introduced a novel way to study the flow of electrons at the interface of the two materials. Using this capability, they found that ion-permeable catalysts form interfaces that yield more energy relative to comparable — but denser — catalysts.
Water splitting provides a potential mechanism for the large-scale conversion and storage of solar energy in the form of a renewable chemical fuel, such as hydrogen. The invention of direct methods to probe charge-separating water-splitting interfaces enables the development of more efficient devices that produce hydrogen from sunlight and water. The discovery also sheds light on fundamental questions regarding charge-transfer at modified interfaces.
A bottleneck in the development of high-efficiency water-splitting solar devices has been a lack of direct, quantitative information regarding the electronic behavior of the interface between the catalyst and semiconductor. To better understand catalysts, researchers electrically contacted a single-crystal titanium dioxide electrode and coated it with various catalyst films. The semiconductor-catalyst interfaces were directly probed as they operated using a new dual-electrode photoelectrochemistry technique to independently monitor and control the voltage and current at both the materials. Using this approach, researchers watched the charge accumulate in the catalyst and change the catalyst’s voltage. Redox-active ion-permeable catalysts, such as nickel hydroxide/nickel oxyhydroxide (Ni(OH)2/NiOOH), yielded “adaptive” semiconductor-catalyst junctions where the effective Schottky barrier height…