Abstract
Synthesis of low cost, durable and efficient electrocatalysts that support oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are the bottlenecks in water electrolysis. Here we propose a strategy for the development of controllably alloyed, porous, and low density nickel (Ni) and cobalt (Co) based alloys - whose electrocatalytic properties can be tuned to make them multifunctional. Ni and Co based alloy with the chemical structure of Ni1Co2 is identified as an efficient OER catalyst among other stoichiometric structures in terms of over potential @ 10 mAcm−2 (1.629 V), stability, low tafel slope (87.3 mV/dec), and high Faradaic efficiency (92%), and its OER performance is also found to be on par with the benchmarked IrO2. Tunability in the porous metal synthesis strategy allowed the incorporation of graphene during the Ni sponge formation, and the Ni- incorporated nitrogen doped graphene sponge (Ni-NG) is found to have very high HER activity. A water electrolysis cell fabricated and demonstrated with these freestanding electrodes is found to have high stability (>10 hours) and large current density (10 mAcm−2 @ 1.6 V), opening new avenues in the design and development of cost effective and light weight energy devices.
Highlights
Rational organization and design of bulk porous multi-metallic architectures are highly demanding and receiving tremendous attention from the scientific community due to their immense applications in energetics[1]
The resultant mixture was poured into a cylindrical crystalline glass dish, which was pre-heated to a temperature of 300 °C using a hot plate in the ambient atmosphere
(C–E) field emission scanning electron microscope (FESEM) images of Ni, Co3O4 and Ni1Co2 sponges respectively. (F) High resolution transmission electron microscope (HRTEM) image of Ni1Co2, (G,H) are the STEM-energy dispersive X-ray spectroscopy (EDS) elemental mapping for Ni and Co in the corresponding TEM image shown in the inset of (F) respectively
Summary
Rational organization and design of bulk porous multi-metallic architectures are highly demanding and receiving tremendous attention from the scientific community due to their immense applications in energetics[1]. Despite the development of numerous metal free 2D materials based catalysts, benchmarked conventional metals in energy technologies are still remain as unbeatable in terms of over potential and long-standing performance[7,8,9]. We propose a single step alloying process for the development of multi-metallic sponges using a template free bulk synthesis method, and demonstrated the performance of these sponges in water electrolysis. Though enormous efforts have been devoted to find effective catalysts, precious metals based catalysts such as RuO2 and IrO2 are still remain as unbeatable for OER23–25. These precious metal oxides are not suitable for large-scale applications and sustainable energy technologies. Development of active (low over potential), durable (stability in the performance), and inexpensive catalysts is of high topical concern
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