Active and Durable Platinum Group Metal-Free Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Systems
Authors: Sayed Doha , Osmieri Luigi , Zelenay Piotr 
Published: December 2024

Net-zero emission energy technologies are urgently needed to mitigate climate change. Generation of “green” hydrogen via low-temperature water electrolysis using renewable electricity and its utilization in fuel cells for power generation when needed is a highly promising path towards achieving zero emission of greenhouse gases [1]. To guarantee the market affordability of low temperature water electrolyzers, cost and performance targets must be met [1]. The need for expensive catalysts based on platinum group metals (PGMs) in proton exchange membrane water electrolyzers (PEMWE) is currently the main obstacle to their widespread deployment. At the same time, liquid alkaline water electrolyzers (LAWE) exhibit the advantage of operation using catalysts based on earth abundant-based elements [2]. The main drawback of LAWE is the use of strongly alkaline and thus corrosive electrolyte (20-40% KOH), which negatively impacts the catalyst durability. The latter limitation comes on top of low current-density operation and losses in the catalyst performance often occurring as a result of current reversal during shut down [3].

Ni-based catalysts, e.g., binary Ni-Mo based materials, display the most promising activity in hydrogen evolution reaction (HER) among non-PGM materials [4]. However, their durability is still a major concern [5]. In one approach, tailoring the design and altering the electronic structure of the NiMo catalysts is an effective route to achieve a higher durability [6].

In this work, we designed a novel and facile synthesis approach to developing binder-free Ni-Mo- phosphide electrocatalysts (Ni-Mo-P) in two steps. In the first step, Ni and Mo were deposited on a Ni-foam substrate from a solution containing complexes of the two metals. In the second step, the deposit was phosphidated via reactive annealing in a presence of phosphorus precursor. The formation of NiMo-phosphide was confirmed by XRD. The thus-synthetized catalysts were electrochemically characterized in a three-electrode cell set-up, showing a decent HER activity. The durability of the catalyst was then assessed for 100 h in 1 M KOH solution under constant current operation, with no activity loss detected. We will compare performance of our catalysts with that of the commercially available Ni and Ni-Mo HER electrocatalysts.

References:

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