Exclusively carbon-based self-supporting electrodes doped with different heteroatoms for overall water splitting in a wide pH range

Carbon-based electrocatalysts are considered as promising catalysts for water separation due to their earth-rich elements, low cost and high catalytic activity. Here, we construct an electrode system based on carbon materials consisting of carbon quantum dots (CQDs) doped with different heteroatoms are integrated on vertically aligned graphene array (VG) (X-VG-CQDs, X = N, S, P, B) as self-supporting electrodes for overall water splitting. The electrochemical performance shows the following pattern: N-VG-CQDs > S-VG-CQDs > P-VG-CQDs > B-VG-CQDs > VG-CQDs. DFT calculations are performed to investigate the correlation between electrochemical performances of various heteroatoms doped of VG-CQDs. The stability test results show that a series of heteroatom-doped VG-CQDs electrodes exhibit more than 50 h stability in a wide pH range. And the Faraday efficiencies of these electrodes for hydrogen evolution reaction are nearly 81%. This study may shed light on the development of efficient cost-effective carbon-based self-supporting electrodes for overall water splitting.