Water electrolysis is considered as the “cleanest” way to produce hydrogen, when the required electricity is derived from renewable energy sources such as solar or wind. To overcome the prohibitive cost barrier to market penetration and to enable widespread deployment of water electrolyzers, it is of paramount importance to develop efficient, cheap, and durable electrocatalysts to expedite hydrogen and oxygen evolution reactions (HER and OER). Notwithstanding remarkable progress in bi-functional electrocatalysts, there are few materials that can simultaneously catalyze HER and OER in the same medium. In this presentation, we report a self-supported three-dimensional macroporous electrode composed of micro/nano-hybrid structures of nickel phosphide – an emerging non-precious electrocatalysts. The electrode is fabricated by a simple, cost-effective, and readily-scalable method, and can be directly used as either cathode or anode in an alkaline electrolyzer. Overall electrochemical water splitting has been realized using an electrolyzer constructed by two identical the as-fabricated electrodes, and a high energy efficiency of 91% is achieved at 10 mA cm^-2. Our finding would significantly simplify the fabrication procedure of water electrolyzers and substantially lower the production costs, given the unique bi-functionality, easy and cost-effective synthetic process of our self-supported nickel phosphide macroporous electrodes.

Figure: SEM image showing the morphology of the self-supported three-dimensional nickel phosphide electrodes.