From Theory to Experiment: Cascading of Thermocatalysis and Electrolysis in Oxygen Evolution Reactions

Abstract

The role of elevated temperatures in electrolysis has generally been regarded as accelerations of electron transport, mass transport, and adsorption/desorption processes. In the present work, with first-principles calculations, we demonstrate that thermally activated on-surface reactions can significantly increase the efficiency of energy conversions in electrolysis via a thermally and electrically cascaded mechanism. In the oxygen evolution reaction (OER), to be specific, the formation of high-energy *OOH on Fe can be assisted by thermally activated combination of *O and *OH on the surface of ironbenzenehexathiol coordination polymer (Fe-BHT). Such theoretical predictions are then confirmed by our experimental measurements. The OER efficiency on Fe-BHT increases with increasing temperature and outperforms the state-of-the-art IrO 2 catalyst at around 80 °C. This research may shed light on an avenue for designing and preparing electrocatalysts with enhanced catalytic performance.

Theoretical Investigation on the Hydrogen Evolution, Oxygen Evolution, and Oxygen Reduction Reactions Performances of Two-Dimensional Metal-Organic Frameworks Fe3(C2X)12 (X = NH, O, S)

“…The optimized atomic structures of *OH, *O, and *OOH intermediates on three Fe-MOF monolayers are diagnosed by considering different adsorbed sites and conformations ( Figures S2–S4 ). It is found that their reaction sites are the same as Fe atoms ( Figure 6 ), which is in agreement with those of other MOF materials [ 22 , 24 ].…”

“…They are ( 1 S4). It is found that their reaction sites are the same as Fe atoms (Figure 6), which is in agreement with those of other MOF materials [22,24]. The OER free energy diagram at 0.00 V, 1.23 V, and work potential is depicted in Figure 6.…”

“…∆G U = eU, where U is the electrode potential, and e is the electron transfer. ∆G pH = k B T × ln10 × pH, where k B is the Boltzmann constant, and pH = 0 in this study, which is the same as previous works [24,31,35,36]; ∆G field is neglected. The entropy and vibrational frequencies of the gas species are taken from the database [49].…”

“…In comparison with the findings of previous studies (Table 2), the Fe-O MOF displays the small or comparable hydrogen adsorption free energy (∆G H = 0.08 eV), implying its excellent HER electrocatalytic activity. [33] 0.14-0.26 --Fe-BHT [24] -0.88 -Zn@InSe [34] 0.02 --Ir 3 (HITP) 2 [35] --0.31 Ni@PR-GDY [36] −0.05 0.29 0.38 Rh 3 (HITP) 2 [35] --0.37…”

“…Mo 3 (C 2 O) 12 MOF could achieve a low limiting potential of -0.36 V for NRR via the distal pathway [22]. These MOFs could also be used as electrocatalysts for ORR [23], OER [24], and HER [25].…”