The appeal of MoS2 begins with its structure. It is a layered transition-metal dichalcogenide in which sheets of molybdenum sandwiched between sulfur planes are stacked by weak van der Waals forces, allowing them to be peeled into atomically thin layers. It exists in three main polymorphs: the semiconducting 2H phase, thermodynamically stable and abundant in nature; the metallic 1T phase, which can be synthesized by chemical intercalation or growth tricks; and the rhombohedral 3R phase, whose broken inversion symmetry gives it distinctive optical behavior. Because bulk 2H-MoS2 has an indirect bandgap while a single layer has a direct one, researchers can tune its electronic and optical properties simply by controlling layer number and phase composition, a flexibility few catalysts offer.

Yet pristine MoS2 has a dirty secret that the review confronts head-on: it is largely inert. Catalysis happens almost exclusively at the edges of the sheets, where molybdenum atoms bind hydrogen with a Gibbs free energy of just 0.08 electron volts, nearly matching platinum’s ideal value of zero. The vast basal planes, meanwhile, do almost nothing. That mismatch between hype and reality is why the authors stress distinguishing genuine intrinsic activity from apparent gains produced by auxiliary components or interfacial effects, a critical eye they bring to every doping strategy they survey.

The physics of why doping works is rooted in the two half-reactions of water splitting. At the cathode, the hydrogen evolution reaction proceeds through a Volmer step, in which protons or water molecules are reduced to adsorbed hydrogen atoms, followed by either a Heyrovsky step, where those atoms react with another proton and electron to release H2, or a Tafel step, where two adsorbed atoms recombine. At the anode, the oxygen evolution reaction demands a punishing four-electron transfer through *OH, *O and *OOH intermediates, making it the kinetic bottleneck of the whole process. Splitting water thermodynamically requires a minimum cell voltage of 1.23 volts, but kinetic overpotentials and ohmic losses push real devices well beyond that. Dopants attack the problem on multiple fronts: they modify electronic structure, improve conductivity, create new active sites and optimize how strongly intermediates bind to the surface.

The review organizes dopants by their position in the periodic table, and the s-block delivers some of the most dramatic transformations. Lithium insertion drives a phase transition from semiconducting 2H to metallic 1T-prime MoS2, and Li0.14MoS2 delivers hydrogen evolution overpotentials of roughly 240 to 280 millivolts at 10 milliamperes per square centimeter with Tafel slopes of 65 to 85 millivolts per decade. Sodium-doped MoS2 nanotubes, grown as ultra-long one-dimensional structures with high surface area, boost charge transfer and have even served as counter electrodes with power conversion efficiencies up to 5.85 percent. On the theoretical side, first-principles calculations show that doping monolayer MoS2 with alkaline earth metals from beryllium to barium narrows the bandgap and shifts optical absorption toward longer wavelengths, with beryllium, magnesium and calcium variants offering the best band structures for photocatalytic water splitting.

P-block doping may be the star of the show. Phosphorus-doped MoS2, prepared by ball-milling with black phosphorus so that phosphorus atoms fill sulfur vacancies, achieves overpotentials as low as 93 millivolts for hydrogen evolution and 316 millivolts for oxygen evolution at 10 milliamperes per square centimeter in alkaline media, with a full water-splitting cell running at about 1.59 volts. Pairing phosphorus doping with a nickel sulfide heterostructure on nickel foam pushes overall splitting down to roughly 1.48 volts. Tin-doped MoS2 grown on nickel foam by microwave-assisted hydrothermal synthesis needs only 149 millivolts for hydrogen evolution and 259 millivolts for oxygen evolution, comfortably beating its undoped counterpart. Computational work on nickel and phosphorus co-doping of the metallic 1T phase predicts a near-ideal hydrogen adsorption free energy of 0.083 electron volts.

Transition-metal dopants from the d-block exploit the interplay between molybdenum’s 4d electrons and the 3d electrons of iron, cobalt, nickel, copper, vanadium, chromium and manganese. Chromium-doped MoS2 nanosheets reach a hydrogen evolution overpotential of 142 millivolts with a Tafel slope of 61 millivolts per decade, indicating a Volmer-Heyrovsky mechanism and faster kinetics than pristine material. A chromium-doped MoS2/WS2 catalyst acts as a robust bifunctional electrode, needing just 145 millivolts for hydrogen evolution and 181 millivolts for oxygen evolution while surviving 72 hours at a punishing 100 milliamperes per square centimeter. Co-doping compounds the gains: iron-cobalt co-doped MoS2 shows Tafel slopes of 50 to 79 millivolts per decade for oxygen evolution, and cobalt-vanadium co-doping yields a hydrogen evolution overpotential of just 86 millivolts, with cobalt activating basal-plane sulfur sites while vanadium tunes hydrogen binding toward thermoneutrality. Perhaps most audacious, a high-entropy alloy of iron, cobalt, nickel, manganese and chromium supported on MoS2 nanosheets delivers oxygen evolution at about 210 millivolts with a Tafel slope of 40.3 millivolts per decade.

Photocatalysis adds a solar dimension to the story. When light strikes a semiconductor, electrons jump to the conduction band and holes remain in the valence band, and if the photon energy exceeds the bandgap, those carriers can respectively reduce water to hydrogen and oxidize it to oxygen. Silver-modified MoS2 nanosheets produce about 1600 micromoles of hydrogen per gram per hour under visible light, a 4.5-fold improvement over pristine MoS2, because silver nanoparticles form Schottky barriers that trap electrons and suppress recombination, with catalytic efficiency reported up to 99 percent and over 90 percent activity retained after 20 hours. A computationally designed cobalt-phosphorus co-doped MoS2 establishes dual active sites, with phosphorus driving oxygen evolution and activated sulfur sites facilitating hydrogen evolution at a near-ideal 0.08 electron volt adsorption energy, while extending photogenerated carrier lifetime from 64 to 123 picoseconds. An 8 percent cobalt-doped 1T/2H mixed-phase catalyst achieves overpotentials of minus 127 millivolts for hydrogen evolution and 292 millivolts for oxygen evolution under sunlight in alkaline media.

Just as important as the performance numbers is the evidence that these catalysts survive real operating conditions. The review catalogues meticulous before-and-after characterization: X-ray photoelectron spectroscopy and extended X-ray absorption fine structure confirm lithium-induced phase transitions, with the molybdenum-molybdenum bond distance shrinking from 3.16 to 2.80 angstroms in the 1T-prime phase; solid-state lithium-7 NMR and in situ infrared spectroscopy with nitric oxide probe molecules track dopant environments and edge sites. Electron paramagnetic resonance verifies the sulfur vacancies that make phosphorus-doped MoS2 active, and post-electrolysis imaging shows lamellar morphology essentially unchanged after long-term testing. Vanadium-doped monolayers grown by chemical vapor deposition hold stable current for 9000 seconds with only a 13 millivolt shift after 500 cycles, while nickel-doped electrodes endure 10,000 seconds of chronoamperometry with negligible degradation.

The synthesis toolbox is equally mature, spanning hydrothermal autoclave reactions at 180 degrees Celsius, chemical vapor deposition for atomically precise doped monolayers, solid-state ion exchange, and microwave-assisted growth directly on conductive nickel foam, meaning these catalysts are not laboratory curiosities but materials with plausible routes to scale. The authors are careful not to oversell: pristine MoS2’s inert basal plane, the complexity of oxygen evolution mechanisms, which in some materials proceed through conventional adsorbate pathways and in others through lattice oxygen participation, and questions of long-term durability all remain open challenges. But the trajectory is unmistakable. By treating the periodic table as a tuning dial, chemists are converting a cheap layered semiconductor once dismissed as mostly inactive into a family of bifunctional electrodes that split water with efficiencies once reserved for platinum and iridium, bringing solar- and electricity-driven green hydrogen a significant step closer to economic reality.

Subject of Research: Doped molybdenum disulfide electrocatalysts and photocatalysts for hydrogen production via water splitting

Article Title: Recent advances in doped MoS2 electrocatalysts and photocatalysts for water splitting

Article References: Nath, A., Paul, S. R., & Patra, S. G. (2026). Recent advances in doped MoS2 electrocatalysts and photocatalysts for water splitting. Discover Electrochemistry, 3(1), Article 47. https://doi.org/10.1007/s44373-026-00133-2

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00133-2

Keywords: MoS2, water splitting, hydrogen evolution reaction, oxygen evolution reaction, electrocatalysis, photocatalysis, doping, transition metal dichalcogenides, green hydrogen, overpotential, phase engineering, renewable energy