Synergistic Electrocatalysts for Alkaline Hydrogen Oxidation and Evolution Reactions

Abstract

Alkaline water electrolyzers (AWEs) and anion-exchange membrane fuel cells (AEMFCs) have received increasing attention for their natural compatibility with earth-abundant materials and are regarded as the cutting-edge of hydrogen energy techniques and the research focuses. However, the commercialization of these devices remains in the sluggish hydrogen electrode reactions due to the requirement of cooperative adsorption of both hydrogen species and hydroxyl species. The research on synergistic alkaline hydrogen oxidation/evolution reaction (HOR/HER) electrocatalysts is still in its infancy. This review summarizes the recent progress and strategies in constructing synergistic active sites for advancing alkaline HOR/HER electrocatalysts. The fundamentals of alkaline HOR/HER are first introduced with both theoretical and experimental verifications to rationalizing the necessity of constructing synergistic active sites. Then, this review systemically dissects the functionality of different active sites in recently reported innovative HOR/HER catalysts and introduces the synergistic effects. Finally, some perspectives on the challenges and opportunities for the future design and synthesis of the synergistic HOR and HER electrocatalysts are proposed, intending to promote the application of hydrogen-based energy conversion systems.

Single‐Atom Molybdenum Engineered Platinum Nanocatalyst for Boosted Alkaline Hydrogen Oxidation

“…HOR kinetics on Pt surface is extremely fast in acidic media even at a loading of 0.05 mg Pt cm −2 or less, but it will be reduced by ≈100 times in alkaline conditions. [5][6][7][8] Hence, higher Pt loadings are required for AEMFCs systems, making the development of HOR catalysts with high efficiency, superior robustness, and less amount/sacrifice of costly Pt resource in alkaline media highly desirable.…”

Boosting the interfacial hydrogen migration for efficient alkaline hydrogen evolution on Pt-based nanowires

“…The proposal is further supported by the CO-stripping curves (Fig. 4d and S22 †), where PtNiP possesses the earliest onset potential for the oxidative removal of CO and therefore the strongest OH À binding 35 in comparison with the PtNi catalyst. Besides, the more polarized and unsymmetrical structure of H 2 O molecules adsorbed on the PtNiP catalyst reects the corresponding facile water dissociation kinetics (Fig.…”

“…The Tafel slope of the PtNi NWs is lower at 39.2 mV dec −1 , which demonstrates that the RDS switches from the Volmer step to the electrochemical desorption step and Ni introduction accelerates the water dissociation kinetics. 35 P-doping further lowers the Tafel slope to 26.6 mV dec −1 for the PtNiP-0.11 NWs, in which the P atoms can promote both the Volmer and desorption steps. The extrapolation of the Tafel plots presents the largest exchange current density at 3.51 mA cm −2 , corresponding to its optimal intrinsic activity (Fig.…”

Green Electrosynthesis of 5,5′‐Azotetrazolate Energetic Materials Plus Energy‐Efficient Hydrogen Production Using Ruthenium Single‐Atom Catalysts

“…Except for the Heyrovsky step, the other key step of water dissociation (Volmer step) is generally considered to be the rate‐determining step for the alkaline HER. [ 55 ] In this regard, a free‐energy diagram of the Volmer step on the surface of MoSe 2 /Ru SA and MoSe 2 /Ru NC at various adsorption sites was proposed. As displayed in Figure 6g and Figure S9, Supporting Information, although the MoSe 2 /Ru SA and MoSe 2 /Ru NC showed similar capacities for promoting the Heyrovsky step at the Se sites (Figure 6f), the energy barrier of the Volmer step for MoSe 2 /Ru NC (1.17 eV) at the Ru sites was significantly lower than that of MoSe 2 /Ru SA (0.87 eV), which indicated superior alkaline HER activity in MoSe 2 /Ru SA than in MoSe 2 /Ru NC.…”