Boosting H₂ Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

Abstract

The sluggish kinetics of oxygen evolution reaction (OER) is the main bottleneck for the electrocatalytic water splitting to produce hydrogen (H2), and the by‐product is worthless O2. Therefore, designing a thermodynamically favorable oxidation reaction to replace OER and coupling with value‐added product generation on the anode is of significance for boosting H2 generation under low electrolysis voltage. Herein, cobalt hydroxide@hydroxysulfide nanosheets on carbon paper (Co(OH)2@HOS/CP) are synthesized as bifunctional electrocatalysts to facilitate H2 production and convert methanol to valuable formate simultaneously. Benefiting from the influences/changes on the composition, surface properties, electronic structure, and chemistry of Co(OH)2, the as‐obtained electrodes exhibit very high selectivity for methanol to value‐added formate oxidation (MFO) and boost electrocatalytic performance with low overpotential of 155 mV for MFO and 148 mV for hydrogen evolution reaction at a current density of 10 mA cm−2. Furthermore, the integrated two‐electrode electrolyzer drives 10 mA cm−2 at a cell voltage of 1.497 V with united 100% Faradaic efficiency for anodic and cathodic reaction and continuous 20 h of operation without obvious decay. The electrocatalytic hydrogen production with the assistance of alternative oxidation by the robust electrocatalyst can be further used to realize the upgrading of other organic molecules with less energy consumption.

Co P@NiCo-LDH heteronanosheet arrays as efficient bifunctional electrocatalysts for co-generation of value-added formate and hydrogen with less-energy consumption

“…The efficiency of charge transfer depends on the surface charge density of electrocatalysts, which governs the activity and selectivity [12 , 14 , 43 , 45 , 50] . Therefore, motivated by the selective electrooxidation of other alcohols [25][26][27][28][29][30][31] , continuous electrolysis is performed at a constant potential of 1.35 V vs. RHE in order to trace the anodic products. As shown in Fig.…”

“…Recently, an efficient strategy has been developed to replace OER by thermodynamic favorable anodic oxidation reaction in water since it can be integrated with HER to generate H 2 with less electrical energy consumption [6-8 , 13] . To realize the coelectrolysis, some reduced agents and organics substrate molecules have been used to optimizing the aqueous electrolyte, such as: urea [18 , 19] , hydrazine [20 , 21] , ammonia [22][23][24] , alcohols [25][26][27][28][29][30][31] , furfural [7 , 13 , 32 , 33] , biomass-derived intermediate compounds [34 , 35] , etc. Comparing to the traditional water electrolysis with HER and OER, these co-electrolysis reactions could significantly decrease operating voltage to produce hydrogen.…”

Hollow NiSe Nanocrystals Heterogenized with Carbon Nanotubes for Efficient Electrocatalytic Methanol Upgrading to Boost Hydrogen Co‐Production

“…Recently, integrating organic upgrading reaction and HER is reported as a promising co‐strategy and mainly represented by the chemical conversions from alcohol hydroxyls/aldehydes to carboxylates. [ 5–8 ] By supplanting sluggish OER, these organic upgrading reactions have been reported for boosting H 2 production with less energy cost, and the value‐added chemicals are obtained simultaneously from various carbon‐based feedstocks. [ 5–8 ]…”

“…[ 10,32–37 ] Among various organic candidates reported for integrating electrocatalytic upgrading and hydrogen co‐generation, methanol is one of the most basic organic molecule with widespread applications owing to its huge capacity, abundant sources, high activity, large volumetric heat capacity, and low price (≈350 €/ton). [ 7,30,38–40 ] Besides, methanol is a liquid C1 model organic molecule with simple structure so that it is of great importance for the basic research on CH, CO, and OH bonds’ activations, alcohol‐water reforming, and electrochemical CC coupling for synthesizing various valuable chemicals from organics. [ 41–44 ] Formic acid and formate salts, as critical intermediates in methanol oxidation process, are widely used in chemical industry with highly added value (>539 €/ton).…”

Cobalt-Based Metal-Organic Frameworks and Their Derivatives for Hydrogen Evolution Reaction

“…Two electrodes of the electrolysis system will play a key role in the hydrogen production. In theory, the decomposition voltage of water is 1.23 V. However, in order to overcome the thermodynamic equilibrium potential, a certain overpotential (η) is required during the practical electrolytic process, which will increase energy consumption (Xiang et al, 2020 ). Generally, highly efficient electrocatalysts could reduce the overpotential and increase the current density of these catalytic reactions (Karmodak and Andreussi, 2020 ; Xu et al, 2020 ).…”