In-depth investigation on the self-catalyzed growth of W2N/In2O3 composite nanowires synthesized via nitrogen plasma assisted in-situ thermal annealing for boosting photoelectrochemical performance

Abstract

Enhancing the charge separation efficiency through interface engineering of In2O3-based photoanodes represents a critical and complex research endeavor in the field of water splitting. Herein, we report a self-catalyzed growth of intrinsic Indium oxide (In2O3) Nanowires (NWs) and Tungsten nitride/Indium oxide (W2N/In2O3) composite nanowires (CNWs) on c-Si substrates by plasma assisted reactive thermal evaporation (PARTE) and nitrogen plasma assisted in-situ thermal annealing, respectively. The nitrogen plasma assisted in-situ thermal annealing effectively transforms the intrinsic In2O3 NWs to W2N/In2O3 CNWs. The optical energy gap, Eg gradually decreases from 2.49 to 2.40 eV when combine with W2N nanostructures. Decrease in the Eg simultaneously increases the photocurrent density of W2N/In2O3 CNWs at V = 0.4 V from 1.9 to 3.8 mA/cm2. This could attribute to the effective electron−hole separations at the interfaces of the heterojunction CNWs. The correlation between the substantially prolonged lifetime of charge carriers and narrowing the bandgap of the composite NWs could be feasible as a good electrochemical electrode. Moreover, the self-catalyzed and secondary growth mechanisms of hierarchically branched In2O3 NWs and W2N/In2O3 CNWs are discussed.