Rhenium-Based Electrocatalysts for Water Splitting

Abstract

Due to the contamination and global warming problems, it is necessary to search for alternative environmentally friendly energy sources. In this area, hydrogen is a promising alternative. Hydrogen is even more promising, when it is obtained through water electrolysis operated with renewable energy sources. Among the possible devices to perform electrolysis, proton exchange membrane (PEM) electrolyzers appear as the most promising commercial systems for hydrogen production in the coming years. However, their massification is affected by the noble metals used as electrocatalysts in their electrodes, with high commercial value: Pt at the cathode where the hydrogen evolution reaction occurs (HER) and Ru/Ir at the anode where the oxygen evolution reaction (OER) happens. Therefore, to take full advantage of the PEM technology for green H 2 production and build up a mature PEM market, it is imperative to search for more abundant, cheaper, and stable catalysts, reaching the highest possible activities at the lowest overpotential with the longest stability under the harsh acidic conditions of a PEM. In the search for new electrocatalysts and considering the predictions of a Trasatti volcano plot, rhenium appears to be a promising candidate for HER in acidic media. At the same time, recent studies provide evidence of its potential as an OER catalyst. However, some of these reports have focused on chemical and photochemical water splitting and have not always considered acidic media. This review summarizes rhenium-based electrocatalysts for water splitting under acidic conditions: i.e., potential candidates as cathode materials. In the various sections, we review the mechanism concepts of electrocatalysis, evaluation methods, and the different rhenium-based materials applied for the HER in acidic media. As rhenium is less common for the OER, we included a section about its use in chemical and photochemical water oxidation and as an electrocatalyst under basic conditions. Finally, concluding remarks and perspectives are given about rhenium for water splitting.

NiMo/CoMoO4 Heterostructure with Confined Oxygen Vacancy for Active and Durable Alkaline Hydrogen Evolution Reaction

“…To analyze the origin of the electrocatalytic activity of the pristine CoMoO 4 and NiMo/CoMoO 4 �directly grown on NF� their ECSA values were determined through C dl 63 at varying scan rates of 0.02 to 0.12 V s −1 (Figure S8). As shown in Figure 4d, the C dl value of NiMo/CoMoO 4 increased almost three-fold relative to pristine CoMoO 4 (2.71 vs 1.14 mF cm −2 ).…”

Self-supporting FeCoMoP nanosheets for efficient overall water splitting

“…The scan rate for the HER polarization curve was 5 mV s À1 , while for the OER and water splitting it was 1 mV s À1 , in order to minimize the background current and the influence of nickel oxidation peaks. Tafel slopes were calculated from the LSV curves, while the double-layer capacitance (C dl ) was obtained by CV at different scan rates (10,20,30,40, and 50 mV s À1 ) within the non-faradaic range (1.12-1.13 V). Electrochemical impedance spectroscopy (EIS) was conducted over a frequency range of 10 5 Hz to 10 À2 Hz.…”

“…[6][7][8] Electrolyzing water to produce hydrogen is a safe and non-polluting method, making it an ideal approach for large-scale hydrogen production. 9,10 Nonetheless, in the process of water electrolysis for hydrogen production, both the HER and the OER exhibit additional overpotentials, leading to an actual water splitting voltage far exceeding the theoretical voltage (1.23 V). 11,12 In particular, the four-electron proton-coupled OER generates additional overpotentials that are particularly difficult to reduce.…”

Tuning Electrochemical Hydrogen-Evolution Activity of CoMoO4 through Zn Incorporation

“…The universally rapid consumption of traditional fossil fuels and the pernicious environmental impacts they create have encouraged researchers to actively and urgently seek a sustainable, renewable, and environmentally friendly energy source as an alternative [1,2]. Electrocatalytic water splitting is a potential approach to convert renewable electricity-generated from renewable energy resources-to hydrogen as a pure, viable, and carbon dioxide-free energy source [3,4]. The efficiency of the water-splitting process is closely dependent on the degree of competence of the electrocatalysts to drive the evolution of the hydrogen (HER) and oxygen (OER) from the medium [5,6].…”