Page 98 - AWSAR 2.0

74 || AWSAR Awarded Popular Science Stories - 2019
The initial challenge we have is to pick a light collector that can absorb most of the sunlight as well as impart stability on light exposure. For that, we chose tiny triangular-shaped (prisms)
gold nanoparticles (30–40 nm
in size) attached to the glass
slide. We selected them as a
light collector because they
could efficiently absorb 95%
of the sunlight, and were very
robust on light exposure. For
the catalyst, we selected an
inexpensive, naturally abundant
cobalt-based (cobaloxime)
molecule: the light collector and
the cobalt-based materials were
connected through a linker. Consequently, the combination
of cobaloxime and tiny prisms
attached through a linker recreated an artificial leaf for water oxidation. The prepared sample looked like a blue sheet and worked as a leaf, and that’s why I called it ‘An artificial blue leaf’.
So now, the question is, how does this blue leaf work? It’s magic. You put this blue leaf into
the water and expose it to sunlight or any other white light source, give some boost (applied potential) and boom ...! The magic happens ... You will see bubbles ... Lots of bubbles due
to the oxygen and hydrogen gas formation. And you will know it is working. The way kids begin dancing and rolling on the trampoline; similarly, the blue leaf comes into action under light exposure. The tiny prismatic gold particles get very excited under light, and the free electrons of the particles start jumping and flowing. As the electrons move, they leave electron holes behind and generate the electron wave, which is then directed to the attached cobalt
catalyst that speeds up the water splitting. As a result, hydrogen and oxygen are produced from water. We found out that the blue leaf we created worked in normal water with high efficiency at minimal overpotential. Therefore, the first challenge about the productivity of the
The high energy density of H2 molecule and efficient extraction of the stored energy via fuel cell also established H2 as one of the most prominent energy vectors in the field. With all this background, now we are set to develop an artificial leaf that will effectively capture solar energy to H2.