Non‐Platinum Group Metal Electrocatalysts toward Efficient Hydrogen Oxidation Reaction

Abstract

Developing non‐platinum group metal (non‐PGM) electrocatalysts for the hydrogen oxidation reaction (HOR) represents the efforts towards the more economical use of hydrogen fuel cells and hydrogen energy, which has attracted tremendous attention recently. However, non‐PGM electrocatalysts for the HOR are still in their early development stages as compared with the significant advances in those for the oxygen reduction reaction and hydrogen evolution reaction. Herein, this paper summarizes the recent progresses and highlights the key challenges for the rational design of non‐PGM electrocatalysts, aiming to promote the development of non‐PGM HOR electrocatalysts. Fundamental understandings of the HOR mechanism are firstly reviewed, where theoretical interpretations on the low HOR kinetics in alkaline media, including the hydrogen binding energy theory, the bifunctional mechanism, and the water molecule reorganization, are particularly discussed. Subsequently, progresses of typical non‐PGM HOR electrocatalysts in acid and alkaline media are summarized separately. For the HOR under alkaline conditions, the superiorities and challenges of Ni‐based catalysts are discussed with a particular focus as they are the most promising non‐PGM electrocatalysts. Finally, this paper highlights the challenges and provide perspectives on the future development directions of non‐PGM HOR electrocatalysts.

Modification of the Intermediate Binding Energies on Ni/Ni3N Heterostructure for Enhanced Alkaline Hydrogen Oxidation Reaction

“…On the other hand, exchange current density (j 0 ) determined by following methods, can be regarded as a vital criterion to evaluate the intrinsic activities of catalysts. [17,22] One method is via Butler-Volmer equation to nonlinearly fit the data of HOR polarization curves in Tafel region (Figure 3b). [38,39] The other is by simplified Butler-Volmer equation to linearly fit the data in micro-polarization region (−10 to 10 mV), as depicted in Figure 3c.…”

Catalyst overcoating engineering towards high-performance electrocatalysis

“…The development of cost-effective non-precious metal based electrocatalysts for the alkaline HOR has fallen far behind that for the ORR and HER. 266 Currently, Ni-based materials are the most studied non-PGM catalysts for the alkaline HOR. 267 Pristine Ni is not active for the alkaline HOR process, which has been widely discussed to be because of its strong affinity to surface intermediates.…”

Synergistic Electrocatalysts for Alkaline Hydrogen Oxidation and Evolution Reactions

“…Notably, Ni is also one of the few non-PGMs that can preserve the metallic nature near the HOR/HER equilibrium potential. [13] However, the HOR is not viable on the monometallic Ni surface due to the too strong hydrogen binding energy and high activation energy barrier for the combination of H ad and OH ad . [40,83,84] The Gibbs free energy of H adsorption (ΔG Had ) on pure Ni was about -0.3 eV, which is slightly away from the thermoneutral state (ΔG Had = 0).…”

“…Although there are several excellent reviews that have summarized the recent advance in HOR and HER in either alkaline or acid media from the catalyst synthesis and structural engineering aspects. [13,15,22,23,[33][34][35] Unfortunately, at present, there is still a lack of systemic protocols for guiding the design of alkaline HOR/HER catalysts across studies. Therefore, we here focus on dissects the functionality of different active sites in synergistic electrocatalysts based on the mechanistic understanding and try to draw on the experience of the scattered reports to give insights for the future rational design of advanced HOR/HER catalysts.…”

“…[10] Generating hydrogen from water by electrochemical water electrolyzers using renewable energy resources and harvesting clean energy by low-temperature membrane-based hydrogen fuel cell technologies are regarded as the cutting-edge of hydrogen energy techniques and the research focuses. [11][12][13] Both hydrogen fuel cells and electrochemical water electrolyzers are heavily reliant on the use of high-performance electrocatalysts for accelerating the reaction rate. Profiting from breakthroughs in many key technologies and the use of platinum group metal (PGM) catalysts, proton exchange membrane (PEM)-based fuel cells (PEMFC) and water electrolyzers have been advanced tremendously in recent years.…”