Ni Foam-Supported NiMo Catalysts for the HER
Authors: Bazan Antony , García Gonzalo , Baena-Moncada Angélica María , Pastor Elena 
Published: July 2022

In the last years, “green hydrogen” fuel had gained a strong relevance due to its potential as friendly-environment energy source to replace fossil fuels. “Green hydrogen” fuel is obtained from water splitting by electrolysis, which can be powered by renewable energy sources, avoiding the emission of CO2 gas as by-product [1]. Particularly, alkaline water splitting has been, extensively, reported as the most sustainable and low-cost route for “green hydrogen” production. However, either oxygen (OER) or hydrogen evolution (HER) half-reaction can be limited by low-relative abundance of noble metals used as commercial electrocatalysts, such as, the benchmarking IrO2||Pt two-electrode couple of 1.57 V at 10 mA cm-2 [2].
Hence the design of non-noble electrocatalysts has gained relevance due to their remarkable electroactivity and high abundance. Mainly, Ni, Fe, Co and/or Mo - based electrocatalysts showed outstanding performance toward the HER. Indeed, theoretical studies indicated that their metallic surfaces promote the hydrogen electro-adsorption as like-metal hydride [M-H], hydroxide [M-OH] and or oxyhydroxide [MOOH] species [3–5]. Consequently, a controlled charge transfer in a two-step mechanism allows a fast electroreduction of water to the desired “green hydrogen” gas.
Herein, we report the synthesis of bimetallic nanostructures, which are produced by thermal-controlled chemical reduction of their precursor salts (NiCl2, Na2MoO4) on the activated nickel foam (NiFA) surface at different highest temperatures (60, 70 and 80 ºC) [4,6]. Therefore, electrocatalysts were labeled as NiMo60/NiFA (60ºC), NiMo70/NiFA (70 ºC) and NiMo80/NiFA (80 ºC). Materials were physicochemical characterized by XRD, SEM, ICP-MS, infrared and Raman spectroscopy, and the HER on the synthesized catalysts in alkaline media was monitored by Differential Electrochemical Mass Spectrometry (DEMS) and in-situ Raman spectroscopy (Fig. a-d).
Main results reveal outstanding electrochemical performance toward the HER on the novel nanomaterials, which is mainly influenced by the highest temperature reached at the synthesis procedure. Furthermore, DEMS indicate similar reaction mechanism for the HER at all catalysts and an increment of the catalytic activity rising the temperature at the synthesis stage.

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Acknowledgments

The Peruvian Fund for Science and Technology (PROCIENCIA) and the Peruvian Minister of Education (MINEDU) by supporting the present work under project 298-2019 FONDECYT and the Doctoral Program with contract 237-2015. The Spanish Ministry of Economy and Competitiveness (MINECO) under project ENE2017-83976 -C2-2-R (FEDER) (co-funded by FEDER). G.G. acknowledges the “Viera y Clavijo” program (ACIISI & ULL), NANOtec, INTech, and Cabildo de Tenerife for laboratory facilities. Authors would like to acknowledge the use of SEGAI—ULL facilities.

Figure 1