Identifying efficient non-precious metal catalysts for oxygen evolution reaction (OER) remains a great challenge. Here we report robust cobalt (oxide) nanoparticles deposited on porous nitrogen-doped carbon (N-carbon) film prepared by pulsed laser deposition under a reactive background gas which exhibit highly efficient OER performance with low overpotential and high stability.The global energy crisis has prompted intense research into the development of various types of sustainable energy conversion and storage systems.1 Splitting water is widely considered to be a critical step toward efficient renewable energy production, storage and usage. One of the major hurdles in making water electrolysis commercially more viable is the low efficiency of the anodic oxygen evolution reaction (OER) and the high cost of conventional OER catalysts such as IrO 2 and RuO 2 .2 Inexpensive and durable "noble metal-free" electrocatalysts such as non-precious metal and metal-free nanostructures, as well as their hybrids, have received much attention recently.3 Among different non-precious metals, cobalt-based materials are promising OER catalysts, however, the easy accumulation and low conductivity of pure cobalt oxides decreases the available active sites and limits charge transport during the oxidation process. 4 On the other hand, various carbon-based materials feature unique advantages due to their tunable molecular structures, abundance, and strong tolerance to acid/alkaline environments. The interplay between carbon and cobalt oxide nanoparticles can modify the overall physicochemical and electronic structures which make the resultant composites highly competitive to traditional cobalt-based electrocatalysts.
5Despite recent progress in developing non-precious metal (specifically cobalt) based hybrid materials, new OER electrocatalysts with low overpotentials and long-term stability are still needed. To overcome these challenges, synthesis techniques are required which ensure high control and tunability of morphology, structure and composition of multi-component materials. Physical vapour deposition (PVD) techniques allow high purity and control in the fabrication of coatings and thin films. In this context, pulsed laser deposition (PLD) is particularly versatile in the tuning of properties of deposited materials 6 which is based on ablating a target material by laser pulses to produce plasma of ejected species that can be deposited onto a substrate. The control of the ablation process permits the tuning of the growth mode and properties of the deposited films over a wide range.