Innovative Strategies for Electrocatalytic Water Splitting

Abstract

Electrocatalytic water splitting driven by renewable energy input to produce clean H has been widely viewed as a promising strategy of the future energy portfolio. Currently, the state-of-the-art electrocatalysts for water splitting in acidic solutions are IrO or RuO for the O evolution reaction (OER) and Pt for the H evolution reaction (HER). Realization of large-scale H production from water splitting requires competent nonprecious electrocatalysts. Despite the advances of decades in this field, several challenges still exist and need to be overcome: (1) Most efforts in the design of nonprecious electrocatalysts have focused on developing HER catalysts for acidic conditions but OER catalysts for alkaline conditions owing to their thermodynamic convenience, potentially resulting in incompatible integration of the two types of catalysts and thus inferior overall performance. (2) In conventional water electrolysis, HER and OER are strictly coupled and therefore H and O are produced simultaneously, which may lead to explosive H/O mixing due to gas crossover. Meanwhile, the coexistence of H, O, and electrocatalysts could produce reactive oxygen species that might shorten the lifetime of an electrolyzer. (3) The HER rate is often limited by that of OER due to the more sluggish kinetics of the latter, which lowers the overall energy conversion efficiency. Moreover, the product of OER, O, is not highly valuable. (4) It remains challenging to develop efficient and low-cost H storage and transport systems for the future H economy. In this Account, we describe recent progress in innovative strategies to address the aforementioned four challenges in conventional water electrolysis. These novel strategies include (1) overall water electrolysis based on bifunctional nonprecious electrocatalysts (or precursors) to drive both HER and OER under the same conditions, (2) decoupled water electrolysis achieved by redox mediators for temporally and spatially separating HER from OER, (3) hybrid water electrolysis by integrating thermodynamically more favorable organic upgrading reactions to replace OER, and (4) tandem water electrolysis by utilizing biocatalysts for converting the in situ produced H with foreign compounds (e.g., CO and N) to more valuable products. Finally, the remaining challenges and future perspectives are also presented. We hope this Account will function as a momentum call for more endeavors into the development of advanced electrocatalytic systems and novel strategies for practicable H production from water as well as the electrocatalytic upgrading of diverse organic compounds.

Construction of Hierarchical Co–Fe Oxyphosphide Microtubes for Electrocatalytic Overall Water Splitting

“…[1,2] Intermittent sustainable energy sources (e.g., solar and wind) can be converted to the versatile and controllable forms through the splitting of water into hydrogen and oxygen. [7] However, the high cost and low abundance of these noble-metal-based materials greatly slow down the pace transfer resistance, which provides new opportunities for the design of highly active electrocatalysts. [7] However, the high cost and low abundance of these noble-metal-based materials greatly slow down the pace transfer resistance, which provides new opportunities for the design of highly active electrocatalysts.…”

Coupling PtNi Ultrathin Nanowires with MXenes for Boosting Electrocatalytic Hydrogen Evolution in Both Acidic and Alkaline Solutions

“…However, the majority of H 2 production in industry today relies on the reforming of fossil reserves, generating a large amount of carbon dioxide. On the contrary, hydrogen evolution reaction (HER), the reductive half reaction of water splitting, provides a clean and renewable way to produce hydrogen at the cost of electric energy . Obviously, developing highly efficient HER electrocatalysts to minimize the overpotential and facilitate the reaction kinetics is one of the prerequisites to realize industrial electrocatalytic hydrogen production in large‐scale …”

Unveiling the Origin of the High Catalytic Activity of Ultrathin 1T/2H MoSe2 Nanosheets for the Hydrogen Evolution Reaction: A Combined Experimental and Theoretical Study

“…[1][2][3][4][5][6] However,t he benchmark hydrogen evolution reaction( HER) suffers from sluggish reactionk inetics owing to additional water dissociation.M any efforts have been devoted to exploring different catalytic systems and the synthesis of high-performance catalysts for improvingt he HER. 2H 2 + O 2 )i se nvisioned to satisfy the globald emandf or clean and renewable energy,a ttracting significant attentionb ecause of its potential to replace fossil fuels.…”