Exploration of isoelectronic substitution in graphene dioxide for photocatalytic and photovoltaic applications – an ab-initio study

Abstract

Herein, we propose graphene dioxide (GDO) derivatives as promising materials for green hydrogen production by photocatalytic water splitting. The optoelectronic and photocatalytic properties of GDO, an insulator with a wide band gap, are tuned by designing new compositions through isovalent substitution of S/Se at the O site, Si and (B,N) at the C site. The newly predicted GDO derivatives were studied using hybrid functional calculations and our results show that several of these materials exhibit semiconducting behavior with a direct band gap value higher than 1.23 eV, hence appropriate for visible light-driven photocatalytic water splitting. The structural stability of these materials was analyzed by total energy and lattice dynamical calculations. The photo generated charge carriers possess lower effective mass and hence higher carrier mobility resulting in suppressed recombination rate and hence improving the water splitting efficiency. Apart from low excitonic binding energy, the electronic structure analysis shows that in several of these compounds the electrons and holes reside in two different atomic sites ensuring further reduction in recombination rate. The relatively higher absorption coefficient of GDO derivatives in the visible part of the solar spectrum indicates enhanced photoconversion efficiency suitable for solar cell applications also and it was further determined by photovoltaic performance parameter analysis. The band edge potential of GDO derivatives is well straddled by the water redox potential at different pHs, suggesting their potential for water splitting along with the possibility of CO₂ reduction. Our findings indicate that the newly predicted compositions hold significant promise for photocatalytic as well as photovoltaic applications.