Surface engineering of nickel selenide for an enhanced intrinsic overall water splitting ability

The development of efficient catalytic electrodes towards the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is at the heart of renewable-energy technologies. Despite the tremendous efforts towards engineering electrode schemes for increasing exposed surface areas and active sites, improving intrinsic catalytic activity still remains a great challenge. Here, we develop a surface-polyaniline (PANI) functionalized nickel selenide (NiSe-PANI) electrode with great performance enhancement for both the HER and OER. The decorated PANI layer subtly modulates the surface electronic structures of NiSe, with a surface-optimized selenium-enriched configuration for the HER and enhanced generation of Ni-III/IV active species when oxidized for the OER. When used as a bifunctional electrocatalyst for overall water splitting, the NiSe-PANI electrode displays excellent performance, with a current density of approximate to 10 mA cm(-2) at an applied voltage of 1.53 V during a long-term electrolysis test, and outperforms the Pt and IrO2 combination as the benchmark and most of the earth-abundant material-based bifunctional catalysts. Similar PANI-functionalization on other bifunctional nickel chalcogenide electrodes also exhibits obviously enhanced performance for overall water splitting, demonstrating the wider applicability of intrinsic activity enhancement via a surface electronic modulation strategy.