Highly efficient electrocatalysts and perovskite solar cells: computer-aided design and experimental demonstration

Abstract

We discuss novel theoretical design of highly efficient energy materials including electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), water splitting, oxygene reduction reaction (ORR), and fuel cells. We find that single atoms (SAs) and nanoparticles (NPs) of transition metals embedded in graphitic carbon sheets and nanotubes synergistically play the key role of high performance electrocatalysts. These SAs+NPs catalysts show very low overpotential as well as impressive stability. Based on first principles prediction, we designed diverse highly efficient electrocatalysts and then performed experiments, verifying the theoretical predictions1,2. We also discuss a hidden role of A-site organic cations in hybrid halide perovskite solar cells which are uncovered with Fröhlich polaron picture based on first principles and many body theory. In Fröhlich polaron picture, A-site organic cations reduce a coupling between photo-excited carriers and lattice, thus enhancing the lifetime of carriers. This provides a design principle of A-site organic cation towards high performance perovskite solar cell material design3. PbI2/AI-terminated lead-iodide-perovskite (APbI3; A=Cs+/ methylammonium(MA)) interfaced with the charge transport medium of graphene or TiO2 is predicted to exhibit the sizable/robust Rashba-Dresselhaus (RD) effect by using DFT and ab initio molecular dynamics (AIMD) simulations at cubic-phase temperature. At the PbI2-terminated graphene/CsPbI3(001) interface, ferroelectric distortion towards graphene facilitates an inversion breaking field. At the MAI-terminated TiO2/MAPbI3(001) interface, the enrooted alignment of MA+ towards TiO2 by short-strong hydrogen-bonding and the concomitant PbI3 distortion preserve the RD interactions even above 330 K. The robust RD effect at the interface even at high temperatures, unlike in bulk, changes the direct-type band to the indirect-type to suppress recombination of electron and hole, thereby letting these accumulated carriers overcome the potential barrier between perovskite and charge transfer materials, which promotes the solar-cell efficiency4.