Fig 1

(a) HOR/HER specific exchange current density of Pt/C in a PEMFC at 353 K compared to that obtained in 0.1 mol∙L−1 KOH and extrapolated to 353 K. (b) HOR overpotential of Pt/C with different mass activity in KOH (black solid lines and gray dashed lines); this is compared with mass activities measured on Pt/C in a PEMFC at 353 K (red lines) 11. Adapted with permission, Copyright 2011, Electrochemical Society, Inc."

Fig 2

Diagram of alkaline HOR/HER mechanisms. (a) Bifunctional Mechanism; (b) HBE Theory; (c) electronic Effect."

Table 1

The theoretical Tafel slope of the rate-determining step in HOR/HER, mechanism of HOR/HER and corresponding Tafel slope (298 K)."

Fig 3

(a) Schematic representation of the HER on Ni(OH)2/Pt(111); (b) comparison between activities for the HER, expressed as overpotential required for a 5 mA∙cm−2 current density, in 0.1 mol∙L−1 HClO4 and 0.1 mol∙L−1 KOH for both bare metal surfaces and Ni(OH)2-modifed surfaces. (b) Adapted with permission 39, Copyright 2012, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim."

Fig 4

(a) HOR polarization curves (black) and CVs (dashed grey and red) for Au(111); (b) HOR polarization curves of Pt/C with 0, 3, 6 and 9 mL doped 5 mmol∙L−1 RuCl3 and Pt1Ru1/C collected in 0.1 mol∙L−1 KOH electrolyte; (c) CO stripping voltammograms collected for Pt/C with various amount of deposited RuCl3 in Ar-saturated 0.1 mol∙L−1 KOH; (d) schematic diagram of Pd/Ni structure (left), and a zoom-in to show the bifunctional catalytic effect of the Pd/Ni surface (right). (a) Adapted with permission 35, Copyright 2013, Nature Publishing Group. (b, c) Adapted with permission 37, Copyright 2017, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (d) Adapted with permission 44, Copyright 2016, Elsevier BV."

Fig 5

(a) Steady state CVs of Pt collected in different pH electrolytes; (b) exchange current densities (i0) normalized to surface area of H1a (peak potential 0.13 V) as a function of t-ECSA; i0 of HOR/HER on Ir/C samples normalized to t-ECSA as a function of t-ECSA. (a) Adapted with permission 49, Copyright 2015, Nature Publishing Group. (b) Adapted with permission 54, Copyright 2015, American Chemical Society."

Fig 6

CO tripping on Pt/C (a) and PtRu/C (b) in 0.1 mol∙L−1 H2SO4 and 0.1 mol∙L−1 KOH solutions; (c) schematic diagram of the cathode-chimney effect for the HER; (d) schematic diagram of anode-chimney effect for the HOR. (a, b) Adapted with permission 61, Copyright 2015, Royal Society of Chemistry. (c) Adapted with permission 62, Copyright 2019, Elsevier BV. (d) Adapted with permission 63, Copyright 2020, Royal Society of Chemistry."

Fig 7

Adsorption energies of (a) H* and (b) H2O* on different metals surfaces with and without OH*; Gibbs free energy change of HOR elementary reaction steps and OH* formation at varied electrode potentials (U, V vs NHE) on (c) Pt(110) and (d) PtRu(110) with and without OH*. (a–d) Adapted with permission 65, Copyright 2019, American Chemical Society."

Fig 8

(a) A snapshot and (b) time evolution of the work function along the trajectory to determine the potential of zero charge equilibrated; (c) electrostatic potential V(z) of Pt(111) in a vacuum (dashed line) and the averaged potential of the Pt(111) electrode with an ion-free water film (solid line). The charge caused by the water film δV (z) is illustrated in the lower panel. (a, b) Adapted with permission 75, Copyright 2018, American Institute of Physics."

Fig 9

Models of water/Pt(100) interface in QMMD simulation. (a) Explicit model (~6 water layers), (b) explicit + Na+ model (~6 water layers + 1Na) and (c) explicit + implicit model (~3 water layers + implicit solvation). (a–c) Adapted with permission 53, Copyright 2018, American Chemical Society."