Abstract
has increased by an average of 1.7 %, which has attained 17.9 TW in
2017 [1]. Projections further estimate this into 22 TW by 2030, an
almost 25 % increase, with fossil fuels accounting for nearly 80 % of the
total [2,3]. The undeniable reliance of the world on fossil fuels has raised
concerns from a sustainability and environmental standpoint. While
thermo and electrocatalysts in the chemical industry have addressed
some issues by reducing energy input, achieving bias-free photocatalytic
overall water splitting (OWS) into hydrogen (H2) and oxygen (O2) remains
a long-term goal for sustainable fuel production [4–8].
Photocatalytic OWS, unlike its highly studied photo-electrochemical
counterpart, eliminates the need for conductive electrolytes
or strong acidic/alkaline solutions. This reduces utilization costs, which
in turn addresses multiple stability and safety concerns [9]. Nevertheless,
challenges exists which are directly related to its narrow visiblelight-
response range and undesirable charge carrier recombination,
resulting in a limited apparent quantum yield (AQY) efficiency (typically
below 15 %) that is reported from literature [10]. The reported
content of UV light in the 300–400 nm region in the solar spectrum is
less than 3 % [11]. Despite almost having 40 % of solar light falling
within the visible spectrum found at 400–700 nm [12], current visiblelight-
responsive (VLR) catalysts are typically limited to 400–485 nm,
hindering energy conversion efficiency [13]. To maximize the efficiency
of photocatalytic water splitting systems, the selection of an appropriate
photocatalyst that can efficiently absorb longer wavelengths of solar
spectrum is very crucial.